Jira:
| Jira Legacy | ||||||||
|---|---|---|---|---|---|---|---|---|
|
Power Validation
Check for continuity between cell inputs, balance inputs, 3 V, 5 V, fused VBAT+ and fused VBAT-. All of these nets should be isolated from each other.
Connect the BMS carrier to the AFE isoSPI port A.
Power the BMS carrier board with 12 V.
Connect the AFE to 12 cells in series, OR connect a power supply between VBAT+ and VBAT-. The power supply can be set to about 30 V with a current limit of about 100 mA.
Measure the voltage between 3 V and VBAT-, and 5 V and VBAT-. 3 V will only be powered when the LTC6811 is awake, so the LTC6811 needs to receive valid ADC commands over isoSPI every 2 s or the REFON bit can be set to 1 with the WRCFGA command, and then the 3 V net can be measured with a DMM. Otherwise, an oscilloscope can be used to measure the 3 V net after a valid ADC command is sent.
Turn off the power supply.
...
Connect the isoSPI port A to a BMS carrier board.
Power the BMS carrier board with 12 V.
Connect the AFE to 12 cells in series.
Measure the cells.
Send the RDCVA, RDCVB, RDCVC, and RDCVD commands (0x00_04, 0x00_06, 0x00_08, and 0x00_0A). The LTC6811 will send back 4 groups of 6 bytes after each command, where each group of two bytes is the cell voltage, starting at cell 1 and increasing to cell 12. Store the result in an array, Cellinitial(n). The voltage of each cell is VCell(n) = Cellinitial(n) * 100 uV.
Send the WRSCTRL command (all low except 1 and 7).
Send the STSCTRL command.
Measure C1-C0, and C7-C6.
Send the CLRSCTRL command.
Repeat the last 4 steps 5 more times for each cell pair.
Send the RDCVA, RDCVB, RDCVC, and RDCVD commands (0x00_04, 0x00_06, 0x00_08, and 0x00_0A). The LTC6811 will send back 24 bytes, where each group of two bytes is the cell voltage, starting at cell 1 and increasing to cell 12. Store the result in an array, Cellfinal(n). The voltage of each cell is VCell(n) = Cellfinal(n) * 100 uV.
Compare the initial voltages to the final voltages. Each cell voltage should have decreased by the same percentage of the cell voltage (the exact amount is dependent on the discharge resistors and MOSFETs). If any cell voltage did not decrease, then that cell’s balancing is not working.
ADC Accuracy
MUX Decoder Channels
Self Test Cell Voltage
Self Test GPIOs
Multiplexer (ADG731)
Connect the BMS carrier to the AFE isoSPI port A.
Power the BMS carrier board with 12 V.
Connect the AFE to 12 cells in series, OR connect a power supply between VBAT+ and VBAT-. The power supply can be set to about 30 V with a current limit of about 100 mA.
Wakeup the LTC6811 by toggling the CS pin from the BMS carrier. To keep the LTC6811 awake, keep toggling the CS pin every second.
Write GPIO bits to 1 so they are not pulled low internally.
Send the WRCOMM command to initiate writing to the communication registers (0x07_21), followed by the PEC. This command expects 6 bytes to be written to the COMM registers. The 6 bytes are divided into 3 groups of 2 bytes, where the first 4 bits sent are the ICOMn[3:0] bits, followed by Dn[7:0], and finally the FCOMn[3:0] bits, where n=0, 1, 2.
The ICOM0[3:0] bits should be 0xA. This sets the GPIOs as a SPI master that toggles the CS high then low at the beginning of communications.
The D0[7:0] is the command to send to the multiplexer, which is 0b000AAAAA where AAAAA is the thermistor to measure (AAAAA can be any value from 0b00000 to 0b11111).
The FCOM[3:0] bits should be 0x9. This sets the CS high after the data is sent.
The ICOM1[3:0] bits should be set to 0xF. This ends the transmission so that the value from the ADC can be read before the next thermistor is selected. All data in the COMM registers after this nibble will be ignored so the rest of the bits can be 0.
After all the data is sent, another PEC must be sent.
Now that the data has been written to the COMM registers, it can be sent to the multiplexer using the STCOMM command, followed by the appropriate number of clock cycles.
Read the ADC value.
Receive data from the COMM registers.
RDCOMM command.