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BQ27426: I2C read register failed

Yuxi Liu(Tony)
Intellectual 2290 points
Part Number: BQ27426
Other Parts Discussed in Thread: BQ25898D, BQSTUDIO

Tool/software:

Hi TIer

My customer use BQ27426 in handheld device.

When he reads the SOC using the I2C command, it has a 50 percent chance of reading the number 0. Our SCL frequency is 40Khz and the pull-up resistance 4.7K ohms (also tried 2k ohms) does not solve the problem.

Could you give me some suggestion? We read SOC continuously, but we have a 50% chance of reading 0

  • 0
    TI__Mastermind 18951 points

    Hello, 

    What is the frequency that you are reading SOC (i.e. every 1s, every 2s, every 3s, ... ect.)? Is there any other devices on the bus when you are trying to communicate with the gauge? Are you able to read other parameters from the gauge without issue? 

    Regards, 

    Jonny. 

  • 0 in reply to Robert
    TI__Intellectual 2290 points

    Customer read SOC in every 1s, on I2C bus , there have BQ25898D and BQ27426 . 

    When the customer reads the BQ27426, it uses a continuous read mode, and the phenomenon is that the starting address REG can be read normally, and then the readback values of several registers around the SOC are 0.

    So I'd like to make sure that the SOC doesn't have a 0 under any circumstances, right? When the real SOC is not 0？

    When we read that the SOC value is 0, what could be the reason?

  • 0 in reply to Yuxi Liu(Tony)
    TI__Mastermind 18951 points

    Hello, 

    Yes, you are correct, the SOC should not report 0 unless the true SOC is 0%. Are you able to provide a bqStudio log file with this behavior displayed? 

    Regards, 

    Jonny. 

  • 0 in reply to Robert
    TI__Intellectual 2290 points

    11.log 
    Tue Jul 23 21:53:38 CST 2024

Device Version Info = 0426_2_02
BQZ Device Name = bq27426G1
BQZ Firmware Version = 2_02


Sample,DateTime,ElapsedTime,Control,CtrlStatus,Temperature,Voltage,Flags,NomAvailCap,FullAvailCap,RemCap,FullChgCap,AvgCurrent,Qmax,AvgPower,Present DOD,StateOfChg,Int Temp,SOH,OCVCurrent,OCVVoltage,SimultCurrent,RemCap UnFlt,RemCap Flt,FullChgCap UnFlt,FullChgCap Flt,True StateOfChg,DOD0,DOD at EOC,True RemCap,Passed Charge,Qstart,DOD_Final,LogRowTime(ms),LogStatus
1,2024-07-23 21:53:44,5.802,0x000C,0x000C,29.75,3891,0x0168,743,1276,735,1268,0,1340,0,7136,58,29.75,0,0,3891,0,735,735,1268,1268,58,7136,616,735,0,533,16123,857,SUCCESS
2,2024-07-23 21:53:46,8.028,0x000C,0x000C,20.05,3600,0x0167,0,1340,0,1340,0,0,0,0,0,29.75,0,0,0,0,0,0,1340,1340,0,0,0,0,0,0,0,927,SUCCESS
3,2024-07-23 21:53:50,12.026,0x000C,0x000C,20.05,3600,0x0167,0,1340,0,1340,0,0,0,0,0,29.75,0,0,0,0,0,0,1340,1340,0,0,0,0,0,0,0,913,SUCCESS
4,2024-07-23 21:53:54,16.038,0x000C,0x008C,29.75,3891,0x01E8,743,1276,735,1268,0,1340,0,7136,58,29.75,0,0,3891,0,735,735,1268,1268,58,7136,616,735,0,533,16123,885,SUCCESS
5,2024-07-23 21:53:58,20.050,0x000C,0x000C,29.75,3892,0x01E9,744,1276,737,1269,0,1340,0,7120,59,29.75,0,0,3892,0,737,737,1269,1269,59,7120,612,737,0,532,16131,904,SUCCESS
6,2024-07-23 21:54:02,24.058,0x000C,0x000C,29.85,3890,0x01EF,0,1340,0,1340,0,1340,0,0,0,29.85,0,0,3890,0,0,0,1340,1340,0,7168,612,0,0,536,16128,914,SUCCESS
7,2024-07-23 21:54:06,28.067,0x009C,,20.05,3600,0x0167,0,1340,0,1340,0,0,0,0,0,-273.15,0,0,0,0,0,0,1340,1340,0,0,0,0,0,0,0,746,ERROR : Please check C:\Users\a0504462\Desktop\11.log.err
8,2024-07-23 21:54:10,32.070,0x000C,0x000C,29.85,3892,0x0168,740,1276,733,1269,0,1340,0,7168,58,29.85,0,0,3892,0,733,733,1269,1269,58,7120,612,733,0,532,16128,870,SUCCESS
9,2024-07-23 21:54:14,36.084,0x000C,0x000C,29.85,3892,0x01E9,744,1276,737,1269,0,1340,0,7120,59,29.85,0,0,3892,0,737,737,1269,1269,59,7120,612,737,0,532,16131,854,SUCCESS
10,2024-07-23 21:54:18,40.090,0x000C,0x000C,20.05,3600,0x016F,0,1340,0,1340,0,0,0,0,0,29.85,0,0,0,0,0,0,1340,1340,0,7136,0,0,0,0,0,896,SUCCESS
11,2024-07-23 21:54:22,44.094,0x008C,0x008C,29.85,3889,0x01E8,745,1276,738,1269,0,1340,0,7104,59,29.85,,0,0,0,0,0,1340,1340,0,0,0,0,0,0,0,909,ERROR : Please check C:\Users\a0504462\Desktop\11.log.err
12,2024-07-23 21:54:26,48.109,0x000C,0x000C,29.95,3891,0x0168,742,1276,735,1269,0,1340,0,7136,58,29.85,0,0,3891,0,735,735,1269,1269,58,7136,612,735,0,534,16123,878,SUCCESS
13,2024-07-23 21:54:30,52.120,0x0000,0x000C,29.85,3895,0x01E9,744,1276,737,1269,0,1340,0,7120,59,29.95,0,0,3892,0,737,737,1269,1269,59,7120,612,737,0,532,16131,897,SUCCESS
14,2024-07-23 21:54:34,56.127,0x000C,0x000C,20.05,3600,0x0167,0,1340,0,1340,0,0,0,0,0,29.95,0,0,0,0,0,0,1340,1340,0,0,0,0,0,0,0,889,SUCCESS
15,2024-07-23 21:54:39,60.141,0x008C,0x008C,29.95,3894,0x01E8,746,1276,739,1269,0,1340,0,7088,59,29.95,0,0,3894,0,739,739,1269,1269,59,7088,612,739,0,530,16124,895,SUCCESS
16,2024-07-23 21:54:43,64.151,0x000C,0x000C,29.95,3890,0x01E9,739,1276,732,1269,0,1340,0,7175,58,29.95,0,0,3890,0,732,732,1269,1269,58,7168,612,733,0,536,16130,918,SUCCESS
17,2024-07-23 21:54:47,68.159,0x000C,0x000C,29.95,3890,0x01E9,746,1276,739,1269,0,1340,0,7088,59,29.95,0,0,3889,0,739,739,1269,1269,59,7175,612,739,0,530,16124,1456,SUCCESS
18,2024-07-23 21:54:51,72.161,0x000C,0x000C,20.05,3600,0x0167,0,1340,0,1340,0,0,0,0,0,29.95,0,0,0,0,0,0,1340,1340,0,0,0,0,0,0,0,857,SUCCESS
19,2024-07-23 21:54:55,76.174,0x000C,0x008C,29.95,3889,0x01E8,748,1276,740,1268,0,1340,0,7072,59,29.95,0,0,3889,0,740,740,1268,1269,58,7175,612,732,0,537,16125,893,SUCCESS
20,2024-07-23 21:54:59,80.187,0x000C,0x000C,29.95,3890,0x01E9,739,1276,732,1269,0,1340,0,7175,58,29.95,0,0,3891,0,732,732,1269,1269,58,7136,612,732,0,537,16125,878,SUCCESS
21,2024-07-23 21:55:03,84.192,0x000C,0x000C,30.05,3890,0x01EF,0,1340,0,1340,0,1340,0,0,0,30.05,0,0,3890,0,0,0,1340,1340,0,7168,612,0,0,536,16128,873,SUCCESS
22,2024-07-23 21:55:07,88.197,0x009C,0x000C,20.05,3600,0x0167,0,1340,0,1340,0,0,0,0,0,30.05,0,0,0,0,0,0,1340,1340,0,0,0,0,0,0,0,929,SUCCESS
23,2024-07-23 21:55:11,92.200,0x000C,0x000C,30.05,3889,0x0168,739,1276,732,1269,0,1340,0,7175,58,29.95,0,0,3889,0,732,732,1269,1269,58,7175,612,732,0,537,16128,879,SUCCESS
24,2024-07-23 21:55:15,96.209,0x000C,0x000C,30.05,3890,0x01E9,739,1276,732,1269,0,1340,0,7175,58,30.05,0,0,3889,0,732,732,1269,1269,58,7175,612,732,0,537,16125,855,SUCCESS
25,2024-07-23 21:55:19,100.216,0x000C,0x000C,20.05,3600,0x016F,0,1340,0,1340,0,0,0,0,0,30.05,0,0,0,0,0,0,1340,1340,0,7104,0,0,0,0,0,895,SUCCESS
26,2024-07-23 21:55:23,104.229,0x008C,0x009C,30.05,3889,0x01E8,740,1276,733,1269,0,1340,0,7168,,-273.15,0,0,0,0,0,0,1340,1340,0,0,0,0,0,0,0,914,ERROR : Please check C:\Users\a0504462\Desktop\11.log.err
27,2024-07-23 21:55:27,108.241,0x000C,0x000C,30.05,3894,0x0168,746,1276,739,1269,0,1340,0,7088,59,30.05,0,0,3894,0,739,739,1269,1269,59,7088,612,739,0,530,16124,898,SUCCESS
28,2024-07-23 21:55:31,112.245,0x000C,0x000C,30.05,3890,0x01E9,739,1276,732,1269,0,1340,0,7175,58,30.05,0,0,3889,0,732,732,1269,1269,58,7175,612,732,0,537,16125,896,SUCCESS
29,2024-07-23 21:55:35,116.261,0x000C,0x000C,20.05,3600,0x0167,0,1340,0,1340,0,0,0,0,0,30.05,0,0,0,0,0,0,1340,1340,0,0,0,0,0,0,0,912,SUCCESS
30,2024-07-23 21:55:39,120.271,0x008C,0x008C,30.05,3890,0x01E8,740,1276,733,1269,0,1340,0,7168,58,30.05,0,0,3890,0,733,733,1269,1269,58,7168,612,733,0,536,16130,856,SUCCESS
31,2024-07-23 21:55:43,124.273,0x000C,0x000C,30.05,3888,0x01E9,746,1276,739,1269,0,1340,0,7088,59,30.05,0,0,3888,0,739,739,1269,1269,59,7184,612,739,0,538,16122,889,SUCCESS
32,2024-07-23 21:55:47,128.279,0x000C,0x000C,30.05,3890,0x01EF,0,1340,0,1340,0,1340,0,0,0,30.05,0,0,3890,0,733,733,1269,1269,58,7168,612,733,0,536,16130,894,SUCCESS
33,2024-07-23 21:55:51,132.293,0x000C,0x000C,20.05,3600,0x0167,0,1340,0,1340,0,0,0,0,0,30.05,0,0,0,0,0,0,1340,1340,0,0,0,0,0,0,0,897,SUCCESS
34,2024-07-23 21:55:55,136.303,0x000C,0x008C,30.05,3894,0x01E8,740,1276,733,1269,0,1340,0,7168,58,30.05,0,0,3894,0,733,733,1269,1269,58,7088,612,739,0,530,16124,870,SUCCESS
35,2024-07-23 21:55:59,140.310,0x000C,0x000C,30.05,3894,0x01E9,739,1276,732,1269,0,1340,0,7175,58,30.05,0,0,3889,0,732,732,1269,1269,58,7175,612,732,0,537,16125,894,SUCCESS
36,2024-07-23 21:56:03,144.320,0x000C,0x000C,30.15,3889,0x01EF,0,1340,0,1340,0,1340,0,0,0,30.05,0,0,3889,0,0,0,1340,1340,0,7175,612,0,0,537,16128,898,SUCCESS
37,2024-07-23 21:56:07,148.329,0x009C,0x000C,20.05,3600,0x0167,0,1340,0,1340,0,0,0,0,0,30.15,0,0,0,0,0,0,1340,1340,0,0,0,0,0,0,0,877,SUCCESS
38,2024-07-23 21:56:11,152.333,0x000C,0x000C,30.15,3888,0x0168,739,1276,732,1269,0,1340,0,7175,58,30.15,0,0,3888,0,732,732,1269,1269,58,7184,612,732,0,538,16128,856,SUCCESS

    11.log.err

    Hi TIer

    Please see the log file , you can see in every time read.

    some case read register and get 0.

    some case can read register good 59% SOC.

  • 0 in reply to Yuxi Liu(Tony)
    TI__Intellectual 2290 points

    I check the I2C waveform too,

    Customer use incremental read mode and read 2 bytes.

    There no issue in hardware side. "写 == W， 读 == R"

  • 0 in reply to Yuxi Liu(Tony)
    TI__Mastermind 18951 points

    Hello, 

    Looking at the log file, it looks like there are several times in which the communication fails. This reporting of 0% for SOC (and it appears there are other parameters that also report 0 frequently) is likely caused to an issue with your bus communication. 

    Regards, 

    Jonny. 

  • 0 in reply to Robert
    TI__Intellectual 2290 points

    Hi Jonny

    It is true that there are some error cases in the log, probably due to the unstable wiring caused by the connect with EV2300 and customer's PCB, but please pay more attention to the successful communication case but other data such as SOC is 0.

    For example, case 2 and 3

    What might be the reason for this obvious anomaly? Or is there a possibility that the log records successful communication and communication failure in fact?

  • 0 in reply to Yuxi Liu(Tony)
    TI__Mastermind 18951 points

    Hello, 

    In the log file you have provided, it seems that the voltage being read by the gauge is very unstable (it seems to be about 3890mV then it seems to drop suddenly to about 3600mV then it rises again). When this significant drop in voltage occurs, the RemCap jumps with it, dropping the RemCap to 0. This then is what is likely causing the SOC to read 0% at some unexpected points. 

    I suggest a good starting point is ensuring the battery has a good connection with your board. Then check your comms lines and ensure that they have a good connection and are configured correctly. 

    Regards, 

    Jonny.