EP3920667A1 - Method for the precise automatic addressing of bus subscribers with applicable self-calibration in a differential can bus system - Google Patents

Abstract

The present invention relates to the field of electrical engineering and electronics and relates to a method for the precise, automatic addressing of BUS subscribers with applicative self-calibration in a differential CAN-BUS system, which is used, for example, to calibrate the control for the auto-addressing of intelligent LED chains can be used in vehicles. The invention is based on the object of providing a method which makes a time-consuming adjustment process unnecessary during the manufacturing process. The object is achieved by a method in which an auto addressing mode is signaled by the CAN-BUS master to the BUS participants and three differential voltage values are measured during a dominant BUS state at each BUS participant, with a first differential voltage value being measured simultaneously on each BUS participant and a second differential voltage value being measured simultaneously on each BUS participant d and a third differential voltage value is measured at each BUS user at the same time. An individual offset and gain error is compensated for for each BUS subscriber and then a self-calibrated differential voltage value is determined with simultaneous transmission of the self-calibrated differential voltage values V _AA from each BUS subscriber to the CAN-BUS master.

Description

The present invention relates to the field of electrical engineering and electronics in particular to the field of physical differential communication interfaces in a linear BUS architecture with a high data rate and relates to a method for the precise, automatic addressing of BUS users with applicative self-calibration in a differential CAN-BUS system.

There are various options for controlling intelligent LED chains. An intelligent LED chain is understood to be a string of LEDs (light emitting diodes), each of which is controlled by an LED driver circuit, i.e. H. an LED controller. As a participant in the LED chain, an LED controller can control one or more LEDs. A central control unit in the LED chain makes it possible, for example, to control and set the radiation intensity (trimming), color, etc. of individual LEDs or of LED groups in the chain using the LED driver circuits.

BUS systems represent a versatile and frequently used solution for controlling LED chains. With such a network structure, a large number of participants, also known as BUS participants, can be integrated into a BUS system to be applied and with the help of a suitable BUS Protocol can be connected via bidirectional communication. For a one-to-one differentiation of the participants within such a BUS system, the fixed position of the participants in the BUS arrangement must be differentiated, which is typically achieved by individual address assignment of each individual participant.

An obvious possibility is to provide each participant with a fixed individual address. Another possibility is to use an additional functional condition in order to be able to distinguish ICs of the same type in such a BUS system at the beginning. Both approaches are through a very high effort and are usually very inflexible, such as B. when exchanging or adding individual BUS participants.

To improve the manageability of BUS structures, different methods for independent, distinguishable addressing have been developed. The principle of auto addressing is already state of the art for LIN-BUS systems. However, the physical characteristics of the LIN-BUS are in some points, such as B. the maximum data rate, the interference immunity or the radiation, limited and not suitable for some applications. Differential BUS structures are significantly more powerful than LIN-BUS systems with regard to many physical properties and, moreover, have better radiation properties. However, comparable methods for automatic addressing, as are known for LIN-BUS systems, are not known for differential BUS structures. A typical differential BUS structure is the CAN-BUS.

An auto-addressing method for differential BUS systems for intelligently controlled LED chains is known from an invention registered at the same time as the present invention. This auto-addressing method enables precise addressing of LED driver ICs in a linear BUS topology, which are arranged in a chain structure and at the same time have a differential interface, without an additional address line. Addressing takes place by evaluating a voltage drop through parasitic or additional line resistances between the participants. For this purpose, both the physical properties of the differential BUS structure that are already present and the standardized signal play of the BUS are used.

The method according to the invention in the invention registered at the same time uses the additional line resistances inserted in the two lines between the BUS subscribers of the CAN-BUS to ensure that a dominant difference level emitted by the BUS master from BUS subscriber to BUS subscriber through these BUS line resistances and the reduced termination resistance at the end of the BUS is slightly lower. These resistors must be designed in such a way that normal CAN-BUS communication is not hindered or disturbed. The position-dependent decrease in the voltage difference level is used to define the BUS subscriber addresses. To do this, all BUS users first measure with a command from the BUS master (short: "InitAA" - IAA) the dominant differential level arriving at you. Then, on a further command from the BUS master (short: "ExecuteAA" - EAA), the simultaneous transmission of these measured values from the BUS users to the BUS master. The BUS subscriber with the lowest measured value can transmit its measured value down to the last bit without collision and saves the lowest address for itself and is excluded from the transmission for the subsequent commands (EAA). The BUS master repeats this command until no more BUS users respond. The subscriber address to be stored in each case correlates to the number of previous collision-prone transmissions. Then all BUS participants have determined their address, the BUS master registers this because of the lack of a response from BUS participants, and the BUS can switch to the normal application mode.

The above-mentioned measurement and evaluation of the voltage drops between the BUS participants requires great accuracy, especially if it is assumed that the total voltage drop across the BUS structure is limited and at the same time a sufficiently large number of BUS participants are involved target. In the prior art, such measurement paths are compared in integrated circuits in the production process by means of automatic test systems, which is often a time-consuming back-end process. It must be reproducible across different machines and locations, include the entire temperature range and have correspondingly low long-term drift.

The present invention is therefore based on the object of providing a method for the precise, automatic addressing of BUS subscribers with applicative self-calibration in a differential CAN-BUS system, which does not have the disadvantages of the prior art described above and which requires a time-consuming adjustment process during of the manufacturing process is unnecessary in order to realize a serial production capability without significant additional effort.

The object is achieved by the invention specified in the patent claims. Advantageous refinements are the subject of the subclaims, wherein the Invention also includes combinations of the individual dependent claims in the sense of an AND link, as long as they are not mutually exclusive.

• Anschalten und/oder Zurücksetzen des CAN-BUS-Systems;
• Signalisieren eines Autoadressierungsmodus durch den CAN-BUS-Master an die BUS-Teilnehmer, die den Autoadressierungsmodus einstellen;
• Messen von drei Differenzspannungswerten während eines dominanten BUS-State an jedem BUS-Teilnehmer, wobei
  • ein erster Differenzspannungswert V_0V von GND gegen GND an jedem BUS-Teilnehmer gleichzeitig gemessen wird,
  • ein zweiter Differenzspannungswert V_CANH von der CANH-Leitung (3) gegen GND an jedem BUS-Teilnehmer gleichzeitig gemessen wird,
  • ein dritter Differenzspannungswert V_CANL von der CANL-Leitung gegen GND an jedem BUS-Teilnehmer gleichzeitig gemessen wird;
• Kompensieren eines individuellen Offsetfehlers für jeden BUS-Teilnehmer durch Subtrahieren des ersten V_0V-Differenzspannungswertes jeweils vom zweiten V_CANH-Differenzspannungswert und vom dritten V_CANL-Differenzspannungswert des jeweiligen BUS-Teilnehmers;
• Kompensieren eines individuellen Gainfehlers für jeden BUS-Teilnehmer (5) mittels eines Korrekturfaktors k_korr, wobei der Korrekturfaktor k_korr aus einem fixen BUS-Referenzwert V_CMRef und den kompensierten V*_CANH- und V*_CANL-Differenzspannungswerten gemäß kkorr = 2 ·V_CMRef / (V*_CANH+ V*_CANL) ermittelt wird;
• Ermitteln eines selbstkalibrierten Differenzspannungswertes V_AA gemäß V_AA = (V_CANH - V_CANL) · k_korr = (V_CANH - V_CANL) · (2·V_CMRef) / (V*_CANH + V*_CANL) durch jeden BUS-Teilnehmer;
• Gleichzeitiges Übermitteln der selbstkalibrierten Differenzspannungswerte V_AA von jedem BUS-Teilnehmer an den CAN-BUS-Master, wobei jeder BUS-Teilnehmer das Übermitteln seines Differenzspannungswertes V_AA solange wiederholt, bis dieser konfliktfrei bis zum letzten Bit an den CAN-BUS-Master übertragen wurde, wobei aus der Reihenfolge der konfliktfrei übermittelten Differenzspannungswerte V_AA mittels einer im CAN-BUS-System bekannten und festgelegten Zuordnungsvorschrift eine BUS-Knotenadresse für jeden BUS-Teilnehmer bestimmt wird.

According to the invention, a method for the precise, automatic addressing of BUS subscribers with applicative self-calibration in a differential CAN-BUS system is specified, the BUS subscribers being arranged linearly along a CAN-BUS and each with a first connection with a CANH line and are connected to a second connection with a CANL line of the CAN-BUS and a CAN-BUS master at the beginning of the CAN-BUS and at least at the end of the CAN-BUS a termination resistor are arranged, the CAN-BUS master and the Terminating resistor connect the CANH line and the CANL line to each other, the procedure has the following steps:

• Switching on and / or resetting the CAN-BUS system;
• Signaling of an auto-addressing mode by the CAN-BUS master to the BUS users who set the auto-addressing mode;
• Measurement of three differential voltage values during a dominant BUS state at each BUS subscriber, whereby
  • a first differential voltage _{value V 0V} from GND to GND is measured simultaneously on each BUS user,
  • a second differential _{voltage value V CANH is measured simultaneously} from the CANH line (3) to GND on each BUS user,
  • a third differential _{voltage value V CANL is measured simultaneously} from the CANL line to GND at each BUS user;
• Compensating for an individual offset error for each BUS subscriber by subtracting the first V _{0V differential voltage value} from the second V CANH differential voltage value and from the third V _{CANL differential voltage value of} the respective BUS subscriber;
• Compensation of an individual gain error for each BUS user (5) by means of a correction factor k _corr , the correction factor k _corr from a fixed BUS reference value V _CMRef and the compensated V * _CANH and V * _{CANL differential voltage values} according to kkorr = 2 · V _CMRef / (V * _CANH + V * _CANL ) is determined;
• Determination of a self-calibrated differential _{voltage value V AA} according to V _AA = (V CANH - V _CANL ) · k _corr = (V _CANH - V _CANL ) · (2 · V _CMRef ) / (V * _CANH + V * _CANL ) by each BUS user ;
• Simultaneous transmission of the self-calibrated differential voltage values V _AA from each BUS subscriber to the CAN-BUS master, with each BUS subscriber _{repeating the transmission of its differential voltage value V AA} until it has been transmitted to the CAN-BUS master without conflict up to the last bit , with a BUS node address being determined for each BUS subscriber from the sequence of the conflict-free transmitted differential _{voltage values V AA} by means of an assignment rule known and defined in the CAN-BUS system.

Advantageously, that BUS subscriber who has transmitted his self-calibrated differential voltage value V _AA to the CAN-BUS master without conflict, blocks his transmission to the CAN-BUS master.

And the process steps are also advantageously controlled automatically and quasi-protocol-controlled by the CAN-BUS master.

With the method according to the invention, it is possible for the first time to specify a method for applicative self-calibration of the measuring arrangement required for the precise, automatic addressing of BUS subscribers in a differential CAN-BUS system, with which a time-consuming adjustment process becomes unnecessary during the manufacturing process of the ICs and which can be realized without problems in a series production without significant additional effort.

This is achieved by a method for applicative self-calibration of a measuring arrangement necessary for auto-addressing in a CAN-BUS system, which is preferably used for and in a CAN-BUS system with auto-addressing. In the CAN-BUS system, the BUS users are along a CAN-BUS arranged linearly and each connected with a first connection with a CANH line and with a second connection with a CANL line of the CAN-BUS. CANH identifies the CAN high potential, CANL identifies the CAN low potential. The order in which the first connections of the BUS users are connected to the CANH line along the CAN-BUS from a CAN-BUS master to a termination resistor is the same as the order in which the second connections of the BUS users are connected to the CANL line along the CAN-BUS from the BUS master to the termination resistor. A CAN-BUS master is arranged at the beginning of the CAN-BUS and a termination resistor is arranged at the end of the CAN-BUS, the CAN-BUS master and the termination resistor connecting the CANH line and the CANL line to one another.

The procedure consists of the following steps:
The prerequisite for performing the self-alignment of the BUS subscriber ICs according to the invention is that the CAN-BUS system must first be switched on and / or reset.

For self-adjustment, three differential voltage values are measured during a dominant BUS state on each BUS user, with a first differential voltage value V _0V from GND to GND being measured simultaneously on each BUS _{user, and a second differential voltage value} V CANH from the CANH line to GND is measured simultaneously at each BUS _{user, and a third differential voltage value} V CANL from the CANL line to GND is measured simultaneously at each BUS user. A termination resistor is located at least at the end of the differential CAN-BUS, which is formed from the CANH and CANL lines. The CAN-BUS master is located at the beginning of the CAN-BUS. The assignment of the beginning and the end of the CAN-BUS are linguistically chosen so that the beginning and the end of a linearly extending CAN-BUS system are identified, whereby it is crucial that the CAN-BUS master has a dominant BUS- State initiates into the CAN-BUS and the termination resistor is arranged at the place that is furthest away from the CAN-BUS master and closes the circuit back to the CAN-BUS master.

In a next step, an individual offset error for each BUS subscriber is compensated for by subtracting the first differential _{voltage value} Vov from the second differential voltage value V CANH and from the third differential _{voltage value} V CANL of the respective BUS subscriber. The offset-compensated differential _{voltage values} are V * CANH and V * _CANL .

An individual gain error for each BUS user is then compensated for by means of a correction factor k _korr , the correction factor k _korr from a fixed BUS reference value V _CMRef and the compensated V * _CANH and V * _CANL differential voltage values according to kkorr = 2 · V _CMRef / (V * _CANH + V * _CANL ) is determined. The BUS reference value V _CMRef can be freely selected. The BUS reference value V _CMRef preferably corresponds to the nominally occurring common mode voltage of the dominant BUS state signal provided by the CAN BUS master in accordance with (V _CANH + VCANL) / 2. The individual _levels V CANH, V _{CANL change} via the BUS, but if the resistance distribution between the CANH and CANL lines is sufficiently uniform over the entire length of the BUS, the common mode voltage does not change in a degenerate manner between the BUS lines. Participants.

In a next step, a self-calibrated differential voltage value V _AA according to V _AA = (V _CANH - V _CANL ) k _korr = (V _CANH - V _CANL ) (2 V _CMRef ) / (V * _CANH + V * _CANL ) is determined in each BUS participant. This completes the self-adjustment of the BUS users. With the method according to the invention it is possible by means of three individual measurements, namely a voltage measurement of 0V / short circuit, of V _CANH and of V _CANL for each BUS user along the CAN-BUS and the subsequent transmissions of all voltage values from the BUS users to the BUS -Master to assign an address to all BUS participants.

In one embodiment of the method, the BUS reference value V _CMRef can be freely selected. In a preferred embodiment of the method _{according to the invention, the BUS reference value V CMRef corresponds to} the nominally occurring common mode voltage of the dominant BUS state signal provided by the BUS master according to (V _CANH + V _CANL ) / 2. The BUS reference value is a fixed value for all BUS users or for all ICs produced with auto-addressing capability _{Normalization of} the measured value of the dominant signal (V CANH - V _CANL ) uses the nominal common mode voltage V _{CM of} the dominant signal from the master (V _{CM_Master} = (V _{CANH_Master} + V _{CANL_Master} ) / 2), which is a typical normalization of 1 results.

In one embodiment of the method, the GND line of the supply for operating the CAN-BUS system is fed in at the BUS end. This ensures that systematically a GND shift that only becomes negative in the direction of the BUS end occurs, which only increases the difference between the measured values of neighboring BUS users and thus ensures more reliable position detection.

The described method for the applicative self-calibration of a measuring arrangement necessary for a localized automatic addressing of BUS users can advantageously be used in the method according to the invention for the localized automatic addressing of BUS users with applicative self-calibration in a differential CAN-BUS system.

The method according to the invention for the precise, automatic addressing of BUS subscribers with applicative self-calibration in a differential CAN-BUS system has the following steps:
First the CAN-BUS system is switched on and / or reset.

The CAN-BUS master then signals to all BUS subscribers (BUS slaves) that auto-addressing is taking place, whereupon the BUS subscribers set an auto-addressing mode, i. H. the auto-addressing is initialized in each BUS subscriber and the task for measuring the differential voltages described below is carried out by each BUS subscriber.

For the first self-adjustment, three differential voltage values are measured during a dominant BUS state on each BUS user, a first differential voltage value V _0V from GND to GND being measured simultaneously on each BUS _{user, and a second differential voltage value} V CANH from the CANH line is measured against GND at each BUS user at the same time, and a third differential _{voltage value} V CANL from the CANL line against GND is measured at each BUS user at the same time. A termination resistor is located at least at the end of the differential CAN-BUS, which is formed from the CANH and CANL lines. The CAN-BUS master is located at the beginning of the CAN-BUS. The assignment of the beginning and the end of the CAN-BUS are linguistically chosen so that the beginning and the end of a linearly extending CAN-BUS system are identified, whereby it is crucial that the CAN-BUS master has a dominant BUS- State initiates into the CAN-BUS and the termination resistor is arranged at the place that is furthest away from the CAN-BUS master and closes the circuit back to the CAN-BUS master.

In a next step, an individual offset error for each BUS subscriber is compensated for by subtracting the first differential _{voltage value} Vov from the second differential voltage value V CANH and from the third differential _{voltage value} V CANL of the respective BUS subscriber. The offset-compensated differential _{voltage values} are V * CANH and V * _CANL .

An individual gain error for each BUS user is then compensated for by means of a correction factor k _korr , the correction factor k _korr from a fixed BUS reference value V _CMRef and the compensated V * _CANH and V * _CANL differential voltage values according to kkorr = 2 · V _CMRef / (V * _CANH + V * _CANL ) is determined. The BUS reference value V _CMRef can be freely selected. The BUS reference value V _CMRef preferably corresponds to the nominally occurring common mode voltage of the dominant BUS state signal provided by the CAN BUS master in accordance with (V _CANH + VCANL) / 2. The individual _levels V CANH, V _{CANL change} via the BUS, but if the resistance distribution between the CANH and CANL lines is sufficiently uniform over the entire length of the BUS, the common mode voltage does not change in a degenerate manner between the BUS lines. Participants.

In a next step, a self-calibrated differential voltage value V _AA according to V _AA = (V _CANH - V _CANL ) k _korr = (V _CANH - V _CANL ) (2 V _CMRef ) / (V * _CANH + V * _CANL ) is determined in each BUS participant.

To carry out the auto-addressing, the self-calibrated differential voltage value is simultaneously used by each BUS subscriber in a next process step V _{AA is} transmitted to the CAN-BUS master, with each BUS subscriber _{repeating the transmission of its differential voltage value V AA} until it has been transmitted to the CAN-BUS master without conflict up to the last bit, with the sequence of the conflict-free transmitted differential voltage values V _{AA is determined} by means of an assignment rule known and defined in the CAN-BUS system, a BUS node address for each BUS subscriber. Based on the previous conflicting measured value transmissions, the BUS users assign themselves a BUS node address. The BUS master can check the correctness of the total number of BUS users if it knows the number of BUS users in the BUS system from the start.

Thus, the inventive method differs significantly z. B. from LIN auto-addressing method, where only one BUS user can be addressed per measurement.

The BUS subscriber who has transmitted his self-calibrated differential voltage value V _AA to the CAN-BUS master without conflict saves the BUS node address that corresponds to the number of conflicting attempts to transmit to the CAN-BUS master and then blocks his transmission the CAN-BUS master.

Accordingly, the self-calibrated differential voltage value V _AA is transmitted from each BUS user to the CAN-BUS master until a valid BUS node address has been assigned to this BUS user.

In one embodiment of the method according to the invention, the process steps are controlled automatically and quasi-protocol-controlled by the CAN-BUS master. The measurement method according to the invention with self-alignment includes, through the application-related approach, a location-dependent, individual offset and gain error correction of the entire measurement paths within the BUS subscribers, the sequence of which takes place automatically within the BUS subscribers and is initiated by the CAN master in a quasi-protocol-controlled manner. The physical levels of the measuring arrangement that are typical of the BUS are also used as stimulating measuring signals, i.e. basically on Basis of the already existing physical properties of the BUS structure. With this type of signal processing, the integrated measuring arrangement can be subject to the usual process and parameter fluctuations and does not have to meet excessive accuracy requirements.

In a further embodiment of the method according to the invention, the BUS users are LED driver circuits that control one or more LEDs. The method according to the invention enables self-calibration for a simpler and more reliable implementation of the auto-addressing of LED chains on the basis of the voltage drop in the BUS lines of the LED driver circuits. This solution only requires BUS communication, but does not require any additional components such as cables, pins, external components, etc.

In summary, the method according to the invention offers the following advantages: No complex adjustment is necessary for the auto-addressing at the end of the manufacturing process of the ICs or in the application. The calibration is independent of both temperature influences and long-term drifts. With the method, individual and location-dependent application properties can be taken into account at the module level. The common mode voltage of the BUS master forms the reference for the self-adjustment of the measuring devices of the BUS participants and makes a high-precision external or internal reference superfluous. Due to the low absolute accuracy requirements that are placed on the measurement of the differential voltages, the procedure can be carried out with an absolutely minimal additional hardware expenditure in the integrated circuit (IC) for the self-adjustment by using the physical properties of the BUS structure that are already present for the measurements be used.

The invention is to be explained in more detail below using exemplary embodiments.

Fig. 1

BUS-Teilnehmer (BUS-Slaves) in einem CAN-BUS-System, das die Spannungsabfälle an jedem BUS-Teilnehmer entlang des BUS für die Autoadressierung nutzt;

Fig. 2

Prinzipielle Struktur des für den Selbstabgleich verwendeten Messverstärkers;

Fig. 3

Schaltungsaufbau des Messverstärkers in SC-Technik zur Durchführung des Verfahrens zur Selbstkalibrierung einer für die Autoadressierung von differentiellen BUS-Schnittstellen notwendigen Messanordnung.

The drawings show

Fig. 1

BUS subscribers (BUS slaves) in a CAN-BUS system that uses the voltage drops at each BUS subscriber along the BUS for auto-addressing;

Fig. 2

Basic structure of the measuring amplifier used for self-adjustment;

Fig. 3

Circuit structure of the measuring amplifier in SC technology for carrying out the method for self-calibration of a measuring arrangement necessary for the auto-addressing of differential BUS interfaces.

the Figure 1 shows a CAN-BUS system 1, which comprises a CAN-BUS 2, which is formed from a CANH line 3 and a CANL line 4. Between the CANH line 3 and the CANL line 4, the BUS subscribers 5 are arranged linearly along the CAN-BUS 2 and each have a first connection to the CANH line 3 and a second connection to the CANL line 4 of the CAN-BUS 2 connected. The sequence of the connection of the first connections of the BUS subscribers to the CANH line 3 along the CAN-BUS 2 from a BUS master 6 to a termination resistor 7 is the same as the sequence of the connection of the second connections of the BUS subscribers 5 to the CANL line 4 along the CAN-BUS 2 from the BUS master 6 to the termination resistor 7. A BUS master 6 at the beginning of the CAN-BUS 2 and a termination resistor 7 at least at the end of the CAN-BUS 2 are arranged, the BUS -Master 6 and the termination resistor 7 connect the CANH line 3 and the CANL line 4 to one another.

The method for self-calibration of a measuring arrangement necessary for auto-addressing or for self-adjustment for automatic addressing of BUS users in a CAN-BUS system is based on Figure 2 explained with the measuring amplifier shown.

gemäß der beispielhaften Struktur des Messverstärkers in Figur 2, wobei r_ln das Teilerverhältnis der Eingangsspannung zum Ausgang des Spannungsteilers 13 bezeichnet. Bei allen drei Messungen wird die Spannung $${\mathrm{V}}_{\mathrm{Add}}\cdot {\mathrm{r}}_{\mathrm{Add}}={\mathrm{V}}_{\mathrm{Add}}\cdot {\mathrm{R}}_{\mathrm{Div}}\cdot {\mathrm{R}}_{\mathrm{In}}/\left({\mathrm{R}}_{\mathrm{In}}\cdot {\mathrm{R}}_{\mathrm{Add}}+{\mathrm{R}}_{\mathrm{Div}}\cdot {\mathrm{R}}_{\mathrm{Add}}+{\mathrm{R}}_{\mathrm{In}}\cdot {\mathrm{R}}_{\mathrm{Div}}\right)$$

mit r_Add = R_Div · R_In / (R_In·R_Add + R_Div·R_Add + R_In·R_Div), was das Teilerverhältnis der Hilfsspannung zum Ausgang des Spannungsteilers 13 bezeichnet, gleichermaßen addiert, wodurch ein Offset des Messverstärkers und der Folgestufen (ADC) für die Messung sicher auf einen positiven Wert gebracht werden soll. So ergeben sich für die drei Messungen entsprechende ADC-Werte für: $${\mathrm{V}}_{\mathrm{M}\mathrm{1}}={\mathrm{V}}_{\mathrm{CANH}}\cdot {\mathrm{r}}_{\mathrm{In}}+{\mathrm{V}}_{\mathrm{Add}}\cdot {\mathrm{r}}_{\mathrm{Add}}$$

$${\mathrm{V}}_{\mathrm{M}\mathrm{2}}={\mathrm{V}}_{\mathrm{CANL}}\cdot {\mathrm{r}}_{\mathrm{In}}+{\mathrm{V}}_{\mathrm{Add}}\cdot {\mathrm{r}}_{\mathrm{Add}}\mathrm{und}$$

$${\mathrm{V}}_{\mathrm{M}\mathrm{3}}={\mathrm{V}}_{\mathrm{GND}}\cdot {\mathrm{r}}_{\mathrm{In}}+{\mathrm{V}}_{\mathrm{Add}}\cdot {\mathrm{r}}_{\mathrm{Add}}$$

Nun erfolgt die digitale Verrechnung der Werte gemäß: $${\mathrm{V}}_{\mathrm{M}\mathrm{13}}={\mathrm{V}}_{\mathrm{M}\mathrm{1}}-{\mathrm{V}}_{\mathrm{M}\mathrm{3}}={\mathrm{V}}_{\mathrm{CANH}}\cdot {\mathrm{r}}_{\mathrm{In}}$$

$${\mathrm{V}}_{\mathrm{M}\mathrm{23}}={\mathrm{V}}_{\mathrm{M}\mathrm{2}}-{\mathrm{V}}_{\mathrm{M}\mathrm{3}}={\mathrm{V}}_{\mathrm{CANL}}\cdot {\mathrm{r}}_{\mathrm{In}}$$

das sind nun die vom Offset bereinigten Messwerte für CANH und CANL. _{The measurement voltages V meas} processed by the measurement amplifier are fed to an ADC, which is usually already present, to carry out the measurements and then used for auto-addressing after the process-based calculation of the individual measurement values. For the procedure, three individual measurements are initially carried out during a dominant BUS state, namely for the potentials of CANH, CANL and GND, divided over $${\mathrm{r}}_{\mathrm{In}}={\mathrm{R.}}_{\mathrm{Div}}\cdot {\mathrm{R.}}_{\mathrm{Add}}/\left({\mathrm{R.}}_{\mathrm{In}}\cdot {\mathrm{R.}}_{\mathrm{Add}}+{\mathrm{R.}}_{\mathrm{Div}}\cdot {\mathrm{R.}}_{\mathrm{Add}}+{\mathrm{R.}}_{\mathrm{In}}\cdot {\mathrm{R.}}_{\mathrm{Div}}\right)$$

according to the exemplary structure of the measuring amplifier in Figure 2 , where r _ln denotes the division ratio of the input voltage to the output of the voltage divider 13. For all three measurements, the voltage becomes $${\mathrm{V}}_{\mathrm{Add}}\cdot {\mathrm{r}}_{\mathrm{Add}}={\mathrm{V}}_{\mathrm{Add}}\cdot {\mathrm{R.}}_{\mathrm{Div}}\cdot {\mathrm{R.}}_{\mathrm{In}}/\left({\mathrm{R.}}_{\mathrm{In}}\cdot {\mathrm{R.}}_{\mathrm{Add}}+{\mathrm{R.}}_{\mathrm{Div}}\cdot {\mathrm{R.}}_{\mathrm{Add}}+{\mathrm{R.}}_{\mathrm{In}}\cdot {\mathrm{R.}}_{\mathrm{Div}}\right)$$

with r _Add = R _Div * R _In / (R _In * R _Add + R _Div * R _Add + R _In * R _Div ), which denotes the divider ratio of the auxiliary voltage to the output of the voltage divider 13, is also added, creating an offset of the measuring amplifier and the following stage (ADC) for the measurement should be safely brought to a positive value. This results in corresponding ADC values for the three measurements for: $${\mathrm{V}}_{\mathrm{M.}\mathrm{1}}={\mathrm{V}}_{\mathrm{CANH}}\cdot {\mathrm{r}}_{\mathrm{In}}+{\mathrm{V}}_{\mathrm{Add}}\cdot {\mathrm{r}}_{\mathrm{Add}}$$

$${\mathrm{V}}_{\mathrm{M.}\mathrm{2}}={\mathrm{V}}_{\mathrm{CANL}}\cdot {\mathrm{r}}_{\mathrm{In}}+{\mathrm{V}}_{\mathrm{Add}}\cdot {\mathrm{r}}_{\mathrm{Add}}\mathrm{and}$$

$${\mathrm{V}}_{\mathrm{M.}\mathrm{3}}={\mathrm{V}}_{\mathrm{GND}}\cdot {\mathrm{r}}_{\mathrm{In}}+{\mathrm{V}}_{\mathrm{Add}}\cdot {\mathrm{r}}_{\mathrm{Add}}$$

The values are now digitally offset according to: $${\mathrm{V}}_{\mathrm{M.}\mathrm{13th}}={\mathrm{V}}_{\mathrm{M.}\mathrm{1}}-{\mathrm{V}}_{\mathrm{M.}\mathrm{3}}={\mathrm{V}}_{\mathrm{CANH}}\cdot {\mathrm{r}}_{\mathrm{In}}$$

$${\mathrm{V}}_{\mathrm{M.}\mathrm{23}}={\mathrm{V}}_{\mathrm{M.}\mathrm{2}}-{\mathrm{V}}_{\mathrm{M.}\mathrm{3}}={\mathrm{V}}_{\mathrm{CANL}}\cdot {\mathrm{r}}_{\mathrm{In}}$$

these are now the measured values for CANH and CANL that have been cleared of the offset.

Der Korrekturfaktor für diese Differenzspannung ergibt sich nach: $${\mathrm{k}}_{\mathrm{korr}}=\mathrm{2}\cdot {\mathrm{V}}_{\mathrm{CMRef}}/\left({\mathrm{V}}_{\mathrm{M}\mathrm{13}}+{\mathrm{V}}_{\mathrm{M}\mathrm{23}}\right)=\mathrm{2}\cdot {\mathrm{V}}_{\mathrm{CMRef}}/\left(\left({\mathrm{V}}_{\mathrm{CANH}}+{\mathrm{V}}_{\mathrm{CANL}}\right)\cdot {\mathrm{r}}_{\mathrm{In}}\right)$$

wobei V_CMRef eine im Prinzip beliebig festlegbare Spannung ist, vorzugsweise aber der nominalen Common Mode Spannung entsprechen sollte.The differential voltage to be compensated results from $${\mathrm{V}}_{\mathrm{Diff}\mathrm{12th}}={\mathrm{V}}_{\mathrm{M.}\mathrm{1}}-{\mathrm{V}}_{\mathrm{M.}\mathrm{2}}={\mathrm{V}}_{\mathrm{M.}\mathrm{13th}}-{\mathrm{V}}_{\mathrm{M.}\mathrm{23}}=\left({\mathrm{V}}_{\mathrm{CANH}}-{\mathrm{V}}_{\mathrm{CANL}}\right)*{\mathrm{r}}_{\mathrm{In}}\mathrm{.}$$

The correction factor for this differential voltage results from: $${\mathrm{k}}_{\mathrm{corr}}=\mathrm{2}\cdot {\mathrm{V}}_{\mathrm{CMRef}}/\left({\mathrm{V}}_{\mathrm{M.}\mathrm{13th}}+{\mathrm{V}}_{\mathrm{M.}\mathrm{23}}\right)=\mathrm{2}\cdot {\mathrm{V}}_{\mathrm{CMRef}}/\left(\left({\mathrm{V}}_{\mathrm{CANH}}+{\mathrm{V}}_{\mathrm{CANL}}\right)\cdot {\mathrm{r}}_{\mathrm{In}}\right)$$

where V _{CMRef is} in principle a voltage that can be determined as desired, but should preferably correspond to the nominal common mode voltage.

The corrected differential voltage for a BUS subscriber 5 now results simply from: $${\mathrm{V}}_{\mathrm{corr}}={\mathrm{k}}_{\mathrm{corr}}\cdot {\mathrm{V}}_{\mathrm{Diff}\mathrm{12th}}=\mathrm{2}\cdot {\mathrm{V}}_{\mathrm{CMRef}}\cdot \left({\mathrm{V}}_{\mathrm{CANH}}-{\mathrm{V}}_{\mathrm{CANL}}\right)/\left({\mathrm{V}}_{\mathrm{CANH}}+{\mathrm{V}}_{\mathrm{CANL}}\right)={\mathrm{V}}_{\mathrm{AA}}$$

The most important prerequisite for the function of a self-adjustment is the presence of a reference that can be used and measured by all BUS users 5 within the individual BUS system 1, for which the common mode voltage of the dominant signal from the master 6 can be used. At each BUS subscriber 5, three individual measurements are required in the dominant BUS state, namely a first voltage measurement between GND and GND, which supplies a first differential voltage value Vov, and a second voltage measurement between CANH and GND, which supplies _{a second differential voltage value V CANH} and a third voltage measurement between CANL _L and GND, which supplies _{a third differential voltage value V CANL.} By subtracting the value from the 0V measurement from the other two measurements, an offset compensation is initially carried out. The measured value to be compensated is the difference between the voltage measurements of V _CANH and V _CANL ( _i.e. V CANH - V _CANL ). The correction factor k _korr for this difference results from the quotient of double the nominal common mode voltage, which is in principle arbitrarily defined, and the sum of the two offset-compensated values for V _CANH and V _CANL , which is double the common provided by the master Mode voltage corresponds to the dominant signal. The product of the difference and the determined correction factor ((V _CANH - V _CANL ) · k _corr ) now results in the comparable value for the differential voltage of V _CANH and V _CANL adjusted within the BUS.

With the method according to the invention, it is therefore possible to carry out a self-adjustment of the BUS users via three individual measurements in order to then start auto-addressing for all BUS users in the CAN-BUS. It is particularly advantageous that absolute accuracy is not required for the voltage measurements. A quasi-arbitrary reference that is only valid within the BUS is used instead of a global absolute reference as it would have to be provided for a tester comparison. One advantage of using the common mode voltage of the dominant signal from the BUS master 6 as a reference is that it is present unchanged at all BUS users 5 at the same time.

In Figure 3 an embodiment of the circuit structure of the measuring amplifier using SC technology to carry out the method for self-calibration of the measuring device for auto-addressing in a CAN-BUS system 1 is shown.

With the proposed method, an adjustment at the end of the IC production on a test system, which requires enormous precision, can be dispensed with.

The self-adjustment of the measuring device for auto-addressing in a BUS application as such does not require absolute accuracy, nor is long-term stability of the variables to be measured required. It is only necessary that all BUS subscribers 5 within a BUS 2 have the same voltage available for measurement at the time of the self-adjustment. This is exactly where the solution for the measurement amplifier and the associated measurement process comes in, thus avoiding completely unnecessary effort and precision on the tester. Only three individual measurements are now required in the dominant BUS state. By subtracting the value of the Vov measurement from the two other measurements (V _CANH , V _CANL ), the offset compensation is initially carried out. Of these two offset-compensated measurements (V * _CANH , V * _CANL ), the quotient of the difference and the sum is now a measure of the BUS differential voltage corrected in the gain, which may only need to be standardized, for example with twice the nominal common -Mode voltage.

The measuring amplifier and the associated measuring method with self-adjustment for CAN-AA + (auto-addressing) can be used for an RGB-LED multichannel PWM controller IC with a CANPhy interface and offers the possibility of an automatic, very precise "adjustment" of the amplifier with regard to offset and gain in the application during / after power-on for the purpose of performing safe auto-addressing in the BUS system 1.

List of reference symbols

1.

CAN-BUS system

2.

CAN-BUS

3.

CAN high line

4th

CAN low line

5.

BUS participant, LED driver circuit

6th

BUS master

7th

Termination resistance

8th.

CANH input

9.

CANL input

10.

GND input

11th

Toggle switch

12th

Auxiliary voltage

13th

Voltage divider

14th

Buffered output voltage from the voltage divider to the analog-digital converter

15th

Buffer operational amplifier

Claims (3)

Method for the precise, automatic addressing of BUS subscribers (5) with applicative self-calibration in a differential CAN-BUS system (1), the BUS subscribers (5) being arranged linearly along a CAN-BUS (2) and each with a first connection with a CANH line (3) and with a second connection with a CANL line (4) of the CAN-BUS (2) and a CAN-BUS master (6) at the beginning of the CAN-BUS (2 ) and at least at the end of the CAN-BUS (2) a termination resistor (7) are arranged, the CAN-BUS master (6) and the termination resistor (7) the CANH line (3) and the CANL line (4 ) connect with each other, the process has the following steps: - Switching on and / or resetting the CAN-BUS system (1); - Signaling of an auto-addressing mode by the CAN-BUS master (6) to the BUS users (5) who set the auto-addressing mode; - Measurement of three differential voltage values during a dominant BUS state at each BUS user (5), whereby - A first differential voltage value Vov from GND to GND is measured at each BUS user (5) at the same time, - a second differential _{voltage value V CANH is measured simultaneously} from the CANH line (3) to GND at each BUS user (5), - A third differential _{voltage value V CANL is measured simultaneously} from the CANL line (4) to GND at each BUS user (5); - Compensating for an individual offset error for each BUS subscriber (5) by subtracting the first Vov differential _{voltage value} from the second V CANH differential voltage value and from the third V _{CANL differential voltage value of} the respective BUS subscriber (5); - Compensation of an individual gain error for each BUS user (5) by means of a correction factor k _korr , the correction factor k _korr from a fixed BUS reference value V _CMRef and the compensated V * _CANH and V * _CANL differential voltage values according to kkorr = 2 · V _CMRef / (V * _CANH + V * _CANL ) is determined; - Determination of a self-calibrated differential _{voltage value V AA} according to V _AA = (V CANH - V _CANL ) k _korr = (V _CANH - V _CANL ) (2 V _CMRef ) / (V * _CANH + V * _CANL ) through each BUS Participant (5); - Simultaneous transmission of the self-calibrated differential voltage values V _AA from each BUS subscriber (5) to the CAN-BUS master (6), with each BUS subscriber (5) _{repeating the transmission of its differential voltage value V AA} until it is free of conflicts up to the last bit is transferred to the CAN bus master (6), from the sequence of conflict-free transmitted differential voltage values V _AA by means of one and the fixed allocation specification known in the CAN-BUS-system (1) comprises a BUS-node address for each bus subscriber (5 ) is determined. Method according to Claim 1, in which the BUS user (5) who _{has transmitted its self-calibrated differential voltage value V AA} to the CAN-BUS master (6) without conflict blocks its transmission to the CAN-BUS master (6). Method according to one of the preceding claims, wherein a sequence control of the method steps takes place automatically and quasi-protocol-controlled by the CAN-BUS master (6).

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