CN111416673A - Method, device and computer readable storage medium for wirelessly measuring Bluetooth frequency offset - Google Patents
Method, device and computer readable storage medium for wirelessly measuring Bluetooth frequency offset Download PDFInfo
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- CN111416673A CN111416673A CN202010222860.5A CN202010222860A CN111416673A CN 111416673 A CN111416673 A CN 111416673A CN 202010222860 A CN202010222860 A CN 202010222860A CN 111416673 A CN111416673 A CN 111416673A
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B17/00—Monitoring; Testing
- H04B17/30—Monitoring; Testing of propagation channels
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L27/00—Modulated-carrier systems
- H04L27/0014—Carrier regulation
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W4/00—Services specially adapted for wireless communication networks; Facilities therefor
- H04W4/80—Services using short range communication, e.g. near-field communication [NFC], radio-frequency identification [RFID] or low energy communication
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L27/00—Modulated-carrier systems
- H04L27/0014—Carrier regulation
- H04L2027/0024—Carrier regulation at the receiver end
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L27/00—Modulated-carrier systems
- H04L27/0014—Carrier regulation
- H04L2027/0024—Carrier regulation at the receiver end
- H04L2027/0026—Correction of carrier offset
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Abstract
The invention provides a method, a device and a computer readable storage medium for wirelessly measuring the Bluetooth frequency offset of master and slave equipment.
Description
Technical Field
The invention relates to the technical field of Bluetooth testing, in particular to a method and a device for wirelessly measuring Bluetooth frequency offset of master and slave equipment and a computer readable storage medium.
Background
Currently, a crystal oscillator is used as a clock source in a bluetooth scheme to provide a clock reference for 2.4G RF signals. Due to the manufacturing process level, the crystal oscillators produced by different manufacturers usually have a certain frequency deviation. These fine frequency differences are multiplied by the phase-locked loop and amplified, resulting in a large bluetooth frequency offset.
The bluetooth frequency offset is a difference value between an actual communication carrier frequency and a theoretical communication carrier frequency, when the difference value exceeds a certain range, errors are introduced during signal demodulation, and the communication is unstable or even cannot be communicated due to an overlarge error rate. Therefore, in order to make bluetooth devices manufactured by different manufacturers compatible and stably connected with each other, the bluetooth specification requires that the frequency offset should be controlled within a certain range. In actual production, frequency deviation is difficult to be consistent due to crystal oscillator difference and parasitic capacitance influence. Measuring the bluetooth frequency offset is important in the bluetooth scheme production process.
In the existing scheme for measuring frequency offset, two ways are included:
firstly, the crystal oscillator frequency (or after frequency division of 2.4G signals) is output to a chip pin, and the frequency deviation of low-frequency signals is measured by a frequency meter, the method is simple and direct, but in actual batch production, flying wires need to be welded to an instrument, and then the flying wires are removed after measurement, so that the workload is huge; or the thimble contacts the PCB test point to measure, the test mould needs to be customized, and the process is various.
Secondly, 2.4G signals are directly measured to obtain Bluetooth frequency deviation, the method is complex to measure, high-temperature test equipment such as a frequency spectrograph or a Bluetooth comprehensive tester is needed, the test cost is high, the frequency spectrograph is easily interfered by 2.4G signals (such as an induction cooker, wifi and other Bluetooth) in the surrounding environment in the test process, and the Bluetooth comprehensive tester can resist 2.4G interference, but the equipment cost is high, the operation interface is complex, and the method is not suitable for production operation of workers.
Disclosure of Invention
In view of the above problems, the present invention provides a method, an apparatus, and a computer readable storage medium for wirelessly measuring bluetooth frequency offset of a master device and a slave device, which can conveniently obtain bluetooth frequency offset of a bluetooth device, and have low cost and strong anti-interference performance.
In a first aspect, the present invention provides a method for wirelessly measuring a bluetooth frequency offset, the method comprising the following steps:
s101, establishing Bluetooth connection between the testing device and the device to be tested;
s102, acquiring clock skew of the testing device and the tested device at a first moment, wherein the clock skew is a first clock skew;
s103, at the second moment, acquiring the clock offset of the testing device and the tested device again, wherein the clock offset is the second clock offset;
s104, calculating a change value of the first clock offset and the second clock offset according to the first clock offset and the second clock offset, wherein the change value is a clock offset difference;
and S105, taking a local clock of the testing device as a reference clock, and calculating a frequency offset value of the tested device according to the clock offset difference, the first time and the second time.
Specifically, the local clock C L KN specified by the bluetooth protocol in steps S102 and S103 is generated by the local crystal oscillators of the test apparatus and the device under test.
Specifically, in step S105, the local clock of the test apparatus is used as the reference clock, specifically, the local clock generated by the calibrated local crystal oscillator of the test apparatus is used as the reference clock.
Specifically, the acquiring the clock offset between the testing device and the device under test in steps S102 and S103 includes:
when the test device is used as Bluetooth slave equipment, the test device acquires clock offset at synchronous time when receiving a data packet;
when the test device is used as a Bluetooth master device, the device under test acquires clock offset at synchronous time through the device under test when receiving a data packet, and transmits the clock offset to the test device.
Specifically, the synchronization time is the time when the access code of the classic bluetooth packet is received.
Specifically, the synchronization time is the time when the preamble and the access address of the B L E packet are received.
Specifically, the first time in step S102 is separated from the second time in step S103 by a predetermined time interval.
Specifically, the preset time interval is 0.25-2 s.
In a second aspect, the invention provides a device using the method, which includes the testing device and the device under test, wherein the testing device and the device under test are wirelessly connected through classic bluetooth, and the frequency offset value of the device under test is obtained by obtaining the clock offsets of the testing device and the device under test at different times.
Specifically, the obtaining of the clock skew of the testing device and the device under test at different times includes obtaining, by the testing device/the device under test, the local clock skew at a synchronous time when the testing device/the device under test receives the data packet.
In a third aspect, the invention provides a non-transitory computer readable storage medium storing computer instructions for causing a computer to perform the above method.
Compared with the fly-line measurement in the prior art, the method provided by the invention is simpler and more convenient to operate and has higher efficiency through a wireless connection mode.
The 68bits access code of the classic Bluetooth, the 8bits lead code of the B L E and the 32bits access address of the B L E are unique in Bluetooth communication and can be effectively distinguished from other 2.4G signals.
The frequency offset is calculated by measuring the synchronous time of the data packet twice, compared with a Bluetooth comprehensive tester, the frequency offset measuring method is simpler to realize, the measuring device is low in cost and simple and convenient to operate, and the frequency offset measuring method is suitable for being used in a mass production environment.
Drawings
Fig. 1 is a schematic diagram of steps of a method for wirelessly measuring a bluetooth frequency offset according to an embodiment of the present invention.
Fig. 2 is a timing diagram of clock offset when a device under test has positive frequency offset, where the device under test is used as a slave device according to an embodiment of the present invention.
Fig. 3 is a timing diagram of clock offset when the test apparatus provided in the first embodiment of the present invention is used as a slave device and a negative frequency offset exists in the device under test.
Fig. 4 is a clock offset timing diagram of a device under test with positive frequency offset when the device under test serves as a master device according to an embodiment of the present invention.
Fig. 5 is a clock offset timing diagram of a device under test with negative frequency offset, where the device under test is used as a master device according to an embodiment of the present invention.
Fig. 6A is a timing diagram of clock skew for classical bluetooth packet reception by a master device and a slave device according to an embodiment of the present invention.
Fig. 6B is a timing diagram illustrating clock skew for packet reception by a master device B L E according to an embodiment of the present invention.
Fig. 7 is a flowchart of the apparatus according to the second embodiment of the present invention.
Detailed Description
The technical solution of the present invention will be described clearly and completely with reference to the accompanying drawings in the following embodiments of the present invention, and it is obvious that the described embodiments are only a part of the present invention, and not all of it. Thus, the following detailed description of the present invention, presented in the figures, is not intended to limit the scope of the invention, as claimed, but is merely representative of selected embodiments of the invention. All other embodiments, which can be obtained by a person skilled in the art without any inventive step, are within the scope of the present invention.
The first embodiment is as follows:
the embodiment provides a method for wirelessly measuring bluetooth frequency offset, as shown in fig. 1, the method includes the following steps:
s101, establishing Bluetooth connection between the testing device and the device to be tested;
s102, acquiring clock skew of the testing device and the tested device at a first moment, wherein the clock skew is a first clock skew;
s103, at the second moment, acquiring the clock offset of the testing device and the tested device again, wherein the clock offset is the second clock offset;
s104, calculating a change value of the first clock offset and the second clock offset according to the first clock offset and the second clock offset, wherein the change value is a clock offset difference;
and S105, taking the local clock of the testing device as a reference clock, and calculating the Bluetooth frequency offset of the tested device according to the clock offset difference and the preset time interval.
In the method, the clock offset refers to the offset of a local clock C L KN of the slave device relative to a local clock C L K of the master device in the Bluetooth communication, the Bluetooth protocol provides that the Bluetooth communication is based on the local clock C L K of the master device, when the connection is established, the slave device needs to calculate the clock offset to determine the time when the slave device starts to receive a data packet next time.
In the step S105, the local clock of the testing apparatus is used as the reference clock, which means that the local clock generated by the local crystal oscillator of the testing apparatus is calibrated in advance by a device such as a spectrometer (or a bluetooth integrated tester) to meet the accuracy requirement of the testing device, and the local clock is used as the reference clock of the present invention.
In the step S101, the test apparatus and the device under test establish a connection, specifically, the test apparatus initiates the connection, and the test apparatus maintains the bluetooth connection in the Active state. On the one hand, the device to be tested can be prevented from entering a Sniff state, and the low-frequency crystal oscillator is switched to serve as a clock source to influence a test result. On the other hand, in the Active state, the testing device and the device under test can continuously transmit and receive data packets, so that the clock skew can be acquired subsequently. And when the connection fails, or the connection is disconnected in the test process, the test is regarded as failed.
In the present invention, for the classic bluetooth, the connection is initiated by the testing apparatus, the testing apparatus may initiate a Role Switch request, and when the request is successful, the testing apparatus is changed to a slave apparatus, and the testing apparatus obtains the clock offset, and when part of the tested apparatuses do not allow the Role Switch request, the testing apparatus cannot be changed to the slave apparatus, and the tested apparatuses obtain the clock offset, and then the clock offset is transmitted to the testing apparatus through the bluetooth.
When the test apparatus is used as a slave device, after establishing a bluetooth connection, as described in step S102, the test apparatus acquires the first clock offset2 at the first time, after an interval time elapses, the test apparatus acquires the second clock offset2 at the second time, wherein the interval between the first time and the second time is a predetermined time interval Δ t, and for the classic bluetooth, Δ t is clocked by the local clock of the bluetooth slave device (i.e., the local clock of the test apparatus), and for B L E, this does not exist.
When the test apparatus is used as a slave device, based on the local clock of the test apparatus, if the local clock of the device under test is slightly slower than the local clock of the device under test, as shown in fig. 2, the clock offsets of the local clock of the test apparatus and the device under test become larger, i.e., the second clock offset2> the first clock offset 1. If the device under test has negative frequency offset, as shown in fig. 3, the local clock of the testing device is slightly faster than the local clock of the device under test, and the clock offsets of the two become smaller, i.e. the second clock offset2< the first clock offset 1.
The test device is used as a slave device, when the tested device has positive frequency offset or negative frequency offset, the test device obtains first clock offset and second clock offset at the synchronous moment, and the calculation method of the clock offset difference of the test device and the second clock offset comprises the following steps:
Δoffset＝offset2-offset1(us)
the frequency offset value calculation method of the device to be measured comprises the following steps:
wherein, offset1 is the first clock offset, offset2 is the second clock offset, Δ offset is the difference value of the clock offsets, and offset1, offset2 and Δ offset are signed numbers with unit us; Δ t is the predetermined time interval, in units of us; Δ freq is the frequency offset of the device under test, signed number in ppm.
When the device under test is used as a master device, the device under test acquires the first clock offset1 and the second clock offset2 in the same steps, since the local clock of the device under test has frequency offset, at this time, for the classic bluetooth, Δ t is clocked by the bluetooth master device clock (i.e. the local clock of the device under test), and for B L E, Δ t is clocked by EventCounter (i.e. the connection interval generated by the local clock of the device under test) connected by B L E.
When the test apparatus is used as a master device, with reference to the local clock of the test apparatus, if the local clock of the device under test has a positive frequency offset, as shown in fig. 4, the local clock of the device under test is slightly faster than the local clock of the test apparatus, then the clock offsets of the two will become smaller, i.e. the second clock offset2< the first clock offset 1; if there is a negative frequency offset in the device under test, as shown in fig. 5, the local clock of the device under test is slightly slower than the local clock of the testing device, and the clock offsets of the two become larger, i.e. the second clock offset2> the first clock offset 1.
The testing device is used as a main device, when the tested device has positive frequency deviation or negative frequency deviation, the tested device obtains first clock deviation and second clock deviation at the synchronous moment and transmits the first clock deviation and the second clock deviation to the testing device, and the testing device calculates the clock deviation difference value, wherein the calculating method comprises the following steps:
Δoffset＝offset1-offset2(us)
similarly, the frequency offset value calculation method of the device to be measured comprises the following steps:
the existing bluetooth communication includes classical bluetooth communication and B L E communication, and because the two communication standards are different, in the present invention, the way of acquiring clock skew is different according to the bluetooth communication, and the following describes the different acquiring ways of clock skew under classical bluetooth and B L E, respectively:
when the test device and the device under test are connected by classical bluetooth, the first clock offset and the second clock offset are calculated by measuring the receiving time of the access code of the classical bluetooth data Packet received by the slave device, and referring to fig. 6A, a clock offset acquisition timing diagram between the master device and the slave device is shown, wherein C L K is a local clock of the master device, the period is 312.5us (2C L K periods are 625us, and are described as C L K [27:1] later), C L KN is a local clock of the slave device, a counter with SlotCount 0-624 is self-increased every 1us within 2C L KN periods (described as C L KN [27:1] later), the master device starts sending a data Packet packer at the starting time of C L K, the slave device generally opens a receiving enable RXEN in advance and starts matching the received code stream, and after the access code stream of 68bits is correctly matched, the data Packet is considered to be from the master device, and the slave device under test device latches the corresponding clock offset Δ K measured time of the slave device as a count value of C1625K + sln equivalent to the counter (C1625K # 483 5K + counter) of the master device, C1628K # 12K # 1K, and the slave device under test clock L K (synchronization time).
When the testing apparatus and the apparatus under test are connected through B L E, the first clock offset and the second clock offset are calculated by measuring the receiving time of the B L E packet preamble and the access address received by the slave device, and referring to fig. 6B, which shows a clock offset acquisition timing diagram between the master device and the slave device, the slave device clock C L KN is offset by Δ offset (C L K [27:1] -C L KN [27:1]) × 625+ (n-40) with respect to the master device clock C L K, and the time corresponding to the count value n is the synchronization time of the testing apparatus and the apparatus under test.
After the first clock offset1 and the second clock offset2 are respectively obtained in the above manner, whether the bluetooth frequency offset of the device under test meets the bluetooth specification or not is judged according to the master-slave angle of the testing device and the corresponding clock offset difference value Δ offset calculation method and the frequency offset value Δ freq calculation method of the device under test.
In the Bluetooth specification, the Access Code of classic Bluetooth is a 68bits Code stream generated by a Bluetooth host address, the Preamble of B L E and the Access address are 40bits Code streams, and the Code streams are unique in Bluetooth communication and can be effectively distinguished from other 2.4G signals, and the frequency hopping technology of Bluetooth can allow a plurality of Bluetooth devices to be used simultaneously, so the Bluetooth communication device is very suitable for an environment with more Bluetooth devices on a production line.
In the invention, measurement error is mainly introduced when obtaining offset, and measurement error below +/-1 us. is that an inventor selects different preset time intervals in a test process to obtain the measurement accuracy.
| Predetermined time interval | Measurement error | Conversion to 2.4G Bluetooth frequency offset |
| 2s | (±1us/1000000us)*1000000＝±0.5ppm | ±1.2k |
| 1s | (±1us/1000000us)*1000000＝±1ppm | ±2.4k |
| 0.5s | (±1us/500000us)*1000000＝±2ppm | ±4.8k |
| 0.25s | (±1us/250000us)*1000000＝±4ppm | ±9.6k |
| 0.1s | (±1us/100000us)*1000000＝±10ppm | ±24k |
According to the table, the Bluetooth frequency offset can be measured within 1 second according to higher frequency offset measurement precision (measurement error of +/-1 ppm), and the requirement of rapid test in a Bluetooth product production line can be met. A suitable time interval is preferably 1 second in this embodiment.
Example two:
the embodiment provides a device using the method of the first embodiment, and the device includes a testing device and a device under test, wherein the testing device and the device under test are wirelessly connected through classic bluetooth, and the frequency offset value of the device under test is further obtained by obtaining clock offsets of the testing device and the device under test at different times.
The obtaining of the clock skew of the testing device and the device under test at different times is specifically that when the testing device/the device under test receives a data packet, the testing device/the device under test obtains the local clock skew at a synchronous time. The specific clock offset obtaining method refers to the content described in the first embodiment, and this embodiment is not described in detail.
With reference to the content of the first embodiment, a specific working flow of the device according to this embodiment is as shown in fig. 7, after the test device is started, the device to be tested is automatically scanned around, the device to be tested is started and is close to the test device, and the specific distance control can be implemented by adjusting the transmission power of the test device; after finding the tested device, the testing device establishes Bluetooth connection, then enters a testing mode, and performs Bluetooth frequency offset measurement; the specific measurement method is as described in the first embodiment, after the test device obtains the measurement result, the test device judges the test result, if the test result does not exceed the allowable range of the frequency offset, the test is passed, otherwise, the test is failed, and the test device displays the test result; after the tested device is shut down, the testing device is automatically switched off overtime, and the steps are repeated to carry out the testing process of the next tested device.
Example three:
the present embodiments provide a non-transitory computer-readable storage medium storing computer instructions for causing the computer to perform the above-described method. The method can be understood according to the related description and effects of the content of the above embodiments, and will not be described in detail herein.
In the present invention, a computer readable medium may be a tangible medium that can contain, or store a program for use by or in connection with an instruction execution system, apparatus, or device. The computer readable medium may be a computer readable signal medium or a computer readable storage medium. A computer readable medium may include, but is not limited to, an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or any suitable combination of the foregoing. More specific examples of a computer-readable storage medium would include an electrical connection based on one or more wires, a portable computer diskette, a hard disk, a Random Access Memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), an optical fiber, a portable compact disc read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the foregoing.
The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (11)
1. A method of wirelessly measuring bluetooth frequency offset, the method comprising the steps of:
s101, establishing Bluetooth connection between the testing device and the device to be tested;
s102, acquiring clock skew of the testing device and the tested device at a first moment, wherein the clock skew is a first clock skew;
s103, at the second moment, acquiring the clock offset of the testing device and the tested device again, wherein the clock offset is the second clock offset;
s104, calculating a change value of the first clock offset and the second clock offset according to the first clock offset and the second clock offset, wherein the change value is a clock offset difference;
and S105, taking a local clock of the testing device as a reference clock, and calculating a frequency offset value of the tested device according to the clock offset difference, the first time and the second time.
2. The method according to claim 1, wherein the local clock of steps S102, 103 is a local clock C L KN defined by bluetooth protocol, and is generated by a local crystal oscillator of the testing device and the device under test.
3. The method according to claim 1, wherein the local clock of the test apparatus, specifically the local clock generated by the calibrated local crystal oscillator of the test apparatus, is used as the reference clock in step S105.
4. The method of claim 1, wherein the step S102, 103 of obtaining the clock offset between the testing device and the device under test comprises:
when the test device is used as Bluetooth slave equipment, the test device acquires clock offset at synchronous time when receiving a data packet;
when the test device is used as a Bluetooth master device, the device under test acquires clock offset at synchronous time through the device under test when receiving a data packet, and transmits the clock offset to the test device.
5. The method of claim 4, wherein the synchronization time is an access code completion time of a classic Bluetooth packet.
6. The method of claim 4, wherein the synchronization time is a preamble and access address receiving completion time of a B L E data packet.
7. The method according to any of claims 1-6, wherein the first time of step S102 is separated from the second time of step S103 by a predetermined time interval.
8. The method of claim 7, wherein the predetermined time interval is 0.25-2 s.
9. An apparatus applying the method of any one of claims 1 to 8, comprising the testing apparatus and the device under test, wherein the testing apparatus and the device under test are connected wirelessly through classic bluetooth, and the frequency offset value of the device under test is obtained by obtaining clock offsets of the testing apparatus and the device under test at different times.
10. The apparatus according to claim 9, wherein the obtaining of the clock offsets of the testing apparatus and the device under test at different times is to obtain the local clock offsets at the synchronous times by the testing apparatus/the device under test when the testing apparatus/the device under test receives the data packets.
11. A non-transitory computer readable storage medium storing computer instructions for causing a computer to perform the method of any one of claims 1-8.
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