The Nomura MPPTs have an SPI port that is broken out to pin headers. The SPV1020 datasheet mentions that important cell parameters can be measured via this port, however until now a serious attempt has not been made to get it working.
After connecting the SPI port to a controller board, we were not able to communicate.
Looking at the signals on a logic analyzer, we noticed that the CLK line was actively driven low.
We verified this by checking continuity through CLK and GND, which were directly connected.
Next the SPV1020 chip was removed from the board to see if the SPI port was internally disabled or if the clock being driven low happened on the board. After the hip was removed, CLK was still connected to GND, so the board was inspected under the microscope.
We found 2 traces on the back side of the board (marked JP1 and JP2) that we had previously not looked into, that connected the CLK and MOSI lines to GND. It turns out that the SPV1020 datasheet requires connecting these lines to GND when not in use.
The 2 traces were cut, removing the short between the SPI pins and GND, and we were able to establish an SPI connection with the device. Voltage, current, status, and PWM were all successfully measured, though need to be calibrated to get useful numbers - not unitless hexadecimal corresponding to internal chip ADC values.
Overall, the SPI port does what it claims to do and provides some basic diagnostic information.
We did notice that once the modules go into their overvoltage state (reading 0x03FF), all 10 bit of voltage readings a 1, the chip had to be manually restarted - which could explain some of the issues that we were noticing on the previous car.