CN103051505A - CAN (Controller Area Network) network node time-delay computing method - Google Patents
CAN (Controller Area Network) network node time-delay computing method Download PDFInfo
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- CN103051505A CN103051505A CN201210544866XA CN201210544866A CN103051505A CN 103051505 A CN103051505 A CN 103051505A CN 201210544866X A CN201210544866X A CN 201210544866XA CN 201210544866 A CN201210544866 A CN 201210544866A CN 103051505 A CN103051505 A CN 103051505A
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Abstract
The invention relates to a CAN (Controller Area Network) network node time-delay computing method, namely a sum of two parts, i.e. node input time-delay and node output time-delay is calculated. The CAN network node time-delay computing method comprises the following steps that a false driving station which is at an idle state inputs a standard bit time explicit pulse; a bit time synchronously jumps to an explicit jump edge, and the driving station simultaneously monitors a sixth invisible bit; the bit time sends an initiative error mark to a bus, and the driving station begins to calculate an initial testing time; and the node delay time is calculated by repeatedly testing through a formula standard, namely, Tnode=Tedge-7T. The CAN network node time-delay computing method disclosed by the invention can be used for computing the node delay time more accurately, thereby determining a propagation section in the bit time more accurately and ensuring the correct transmission of signals. According to the CAN network node time-delay computing method disclosed by the invention, the node delay time can be computed by inputting a relationship between the explicit pulse and the invisible bit, so that the propagation section can be better determined, propagation section of the bit time is determined to be not overlong, and the bit rate is limited.
Description
Technical field
The present invention relates to network node and calculate the field, particularly a kind of computational methods of CAN network node time-delay.
Background technology
Controller local area network (Control Area Network; CAN) be the communication protocol of a serial, asynchronous, many main frames, it can connect electronic control module, transducer and actuator in automobile or the commercial Application.The CAN bus is widely used on the automobile, particularly on the electric automobile, is mainly used to realize the information exchange between each ECU (Electrical Control Unit) of In-vehicle networking, forms vehicle netbios.One of them key element of CAN agreement is bit rate, and the bit rate range that it is supported is from 1～1 000 Kb/s.
The inverse of bit rate is bit time, only has bit time to each node to be configured and could produce an identical bit rate.According to the CAN standard, bit time forms by four sections altogether: sync section, propagation segment, phase place breeze way 1 and phase place breeze way 2.Sync section is used for different node on the synchronous bus.This section wished to occur in the period in the hopping edge of CAN bus level.If the hopping edge occurs, then be called the edge phase error beyond this time period.Propagation segment is used for the physics delay time in the compensating network.Phase place breeze way 1 and 2 is used for the mistake in compensation edge stage, and these two sections can lengthen or shortening by re-synchronization.Although can satisfy a given bit rate by different bit time configurations, in order to guarantee the correctness of CAN network function, the physics time-delay is a vital factor.So the node delay of Measurement accuracy CAN system is the key of reasonable disposition CAN bit time.
In addition, propagation segment is used for the physics time-delay in the compensating network, and it is comprised of the signal transmission delay on the bus and inner CAN node delay.Non-destructive arbitration when the propagation delay in the CAN system derives from contention access network between the node and interior the replying of frame.Determining of propagation segment is vital link in the bit timing, and fixed is long, and bit rate is restricted, if fixed too short, can not guarantee the correct transmission of signal, and transmission range also can be restricted.So the Measurement accuracy propagation delay just becomes key, wherein the measurement of bus time-delay is relatively easy, and determines the node delay more complicated.Also there is not at present good method to carry out the node delay measuring and calculating.
Summary of the invention
Based on this, be necessary to provide a kind of computational methods of CAN network node time-delay.
The computational methods of a kind of CAN network node time-delay, i.e. computing node input time delay and node output time-delay two-part and, specifically comprise the steps:
(1) a dominant pulse of normal bit time of active station input that is in the mistake of idle condition;
(2) bit time of described step (1) jumps to dominant hopping edge synchronously, and the active station of described step (1) listens to the 6th stealthy position simultaneously;
(3) bit time of described step (1) sends initiatively error flag to bus, and described active station begins to calculate the initial testing time;
(4) repeatedly test, and by formula T
Node=T
The edge-7T
Standard, calculate the node delay time.
Further, described bit time is comprised of sync section, span line, phase place breeze way 1 and phase place breeze way 2.
Further, phase place breeze way 1 and 2 is used for the mistake in compensation node edge stage, and can lengthen or shortening by re-synchronization.
Further, the stealthy bit time T edge in the formula of described step (4) was comprised of a node input time delay T node, seven normal bit time T standards and clock synchronous time.
Further, the length of described clock synchronous time depends on the clock skew of pulse generator and node, only has the clock different delayed time is tapered to minimum can to calculate the node delay time by following formula.
The present invention has following advantage and beneficial effect with respect to prior art:
The present invention can calculate the node delay time more accurately, thereby determines the propagation segment in the bit time more accurately, guarantees the correct transmission of signal.The present invention calculates the node delay time by the relation of the dominant pulse of input and recessive interdigit, thereby determines propagation segment preferably, is unlikely to longly fixed the propagation segment of bit time, thereby has limited bit rate; Also be unlikely to make the propagation segment of bit time too shortly fixed, thereby affected the correct transmission of signal.
Description of drawings
Fig. 1 is the CAN bus node delay test schematic diagram in one embodiment of the present invention.
Embodiment
As shown in Figure 1, in one embodiment of the present invention, the node delay of CAN system comprises node input time delay and node output time-delay, but for the propagation segment of computing bit time, as long as that can know them and just passable.A dominant pulse that is in a wrong bus input end normal bit time of input of initiatively standing of idle condition, this standing-meeting this moment is thought the start bit of a frame to this dominant position signal, and makes the bit time of oneself be synchronized with this recessiveness to dominant hopping edge.By the time should station " listening " to when position of the 6th recessiveness, it can be thought and has detected a position fill-error and send the active error flag on bus.If the 1st recessive time to that recessive position that dominant error flag begins is T
The edge, T in fact
The edgeBy a node input time delay T
Time-delay, seven normal bit time T
StandardForm with the clock synchronous time.And the length of clock synchronous time depends on the clock skew of pulse generator and CAN node.Only have and clock synchronous time-delay is tapered to minimum can calculate node delay by following formula.In order to make the clock synchronous delay time minimum, namely make the value at edge minimum, so can by adjusting the clock of pulse generator, make T as far as possible
The edgeBe worth littlely, by measuring multi-group data, select minimum value wherein, the formula above utilizing just can calculate T
Node, i.e. node delay time.
The above embodiment has only expressed several execution mode of the present invention, and it describes comparatively concrete and detailed, but can not therefore be interpreted as the restriction to claim of the present invention.Should be pointed out that for the person of ordinary skill of the art without departing from the inventive concept of the premise, can also make some distortion and improvement, these all belong to protection scope of the present invention.Therefore, the protection range of patent of the present invention should be as the criterion with claims.
Claims (5)
1. the computational methods of CAN network node time-delay, i.e. computing node input time delay and node output time-delay two-part and, it is characterized in that, comprise the steps:
(1) a dominant pulse of normal bit time of active station input that is in the mistake of idle condition;
(2) bit time of described step (1) jumps to dominant hopping edge synchronously, and the active station of described step (1) listens to the 6th stealthy position simultaneously;
(3) bit time of described step (1) sends initiatively error flag to bus, and described active station begins to calculate the initial testing time;
(4) repeatedly test, and by formula T
Node=T
The edge-7T
Standard, calculate the node delay time.
2. the computational methods of a kind of CAN network node time-delay according to claim 1 is characterized in that described bit time is comprised of sync section, span line, phase place breeze way 1 and phase place breeze way 2.
3. the computational methods of an a kind of CAN network node time-delay claimed in claim 2 is characterized in that,
Phase place breeze way 1 and 2 is used for the mistake in compensation node edge stage, and can lengthen or shortening by re-synchronization.
4. the computational methods of a kind of CAN network node time-delay according to claim 1 is characterized in that,
Stealthy bit time T in the formula of described step (4)
The edgeBy a node input time delay T
Node, seven normal bit time T
StandardForm with the clock synchronous time.
According to claim 1 with the computational methods of 5 described a kind of CAN network nodes time-delays, it is characterized in that, the length of described clock synchronous time depends on the clock skew of pulse generator and node, only has the clock different delayed time is tapered to minimum can to calculate the node delay time by following formula.
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| Application Number | Priority Date | Filing Date | Title |
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| CN201210544866XA CN103051505A (en) | 2012-12-17 | 2012-12-17 | CAN (Controller Area Network) network node time-delay computing method |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN104092587A (en) * | 2014-07-22 | 2014-10-08 | 中国第一汽车股份有限公司 | CAN network position timing influence factor detection system and method thereof |
| CN107113216A (en) * | 2014-11-21 | 2017-08-29 | 罗伯特·博世有限公司 | For the subscriber station of bus system and for the method for the timing for sending signal for adjusting bus system |
-
2012
- 2012-12-17 CN CN201210544866XA patent/CN103051505A/en active Pending
Non-Patent Citations (1)
| Title |
|---|
| 张杰，薛红卫，徐驰，樊萍，李丽: "测量CAN节点延迟的一种好方法", 《冶金自动化》 * |
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN104092587A (en) * | 2014-07-22 | 2014-10-08 | 中国第一汽车股份有限公司 | CAN network position timing influence factor detection system and method thereof |
| CN104092587B (en) * | 2014-07-22 | 2017-07-04 | 中国第一汽车股份有限公司 | CAN network bit timing influence factor detecting system and its method |
| CN107113216A (en) * | 2014-11-21 | 2017-08-29 | 罗伯特·博世有限公司 | For the subscriber station of bus system and for the method for the timing for sending signal for adjusting bus system |
| CN107113216B (en) * | 2014-11-21 | 2020-07-03 | 罗伯特·博世有限公司 | Subscriber station and method for adjusting the timing of a transmission signal of a bus system |
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Application publication date: 20130417 |