NXP AFE slave PCB - supports only 8 temp sensors - no redundancy like the LTC version #73
Description
I might be wrong. and this issue could simply be a check that I got the software code and PCB design correctly. But this is what I noticed:
Hardware
The secondary temp sensors multiplexer is connected to GPIO2 which belongs to the same ADC within the AFE as GPIO0 used for the primary multiplexer, and hence may not be suitable for SIL 3 or higher required redundancy. connecting the secondary multiplexer to GPIO4 to GPIO7 could be necessary to achieve redundancy.
Software
Even though the software can read the AIN2 (GPIO2) register and store its value within allGpioVoltage results, that value is not used later to be converted to a temperature and the secondary multiplexer does not seem to ever be selected nor used. (N775_MULTIPLEXER_TEMP_GPIO_POSITION)
Basically the secondary temp sensor connector and its corresponding secondary multiplexer seem to be there as a dummy circuit and not actually used within software, nor it is routed in an ASIL D redundant compatible way within the PCB