Hi Didier,
first - an additional question from my side. Your expansion board where I2C TI PCF8574A is mounted works currently in combination with an ArmstoneA9r3? That's stange! As far as I see (all) previous armStones have no I2C option at all on FC.29, FC.31 (refer HW doc). There is only AIN available. Else please provide me the serial number of ArmstoneA9r3 so that I can double check.
>>1. can you explain me what AIN stands for, what is its purpose?
<< Analog Input (ADConverter). There are ADS1015 mounted and AIN0...3 available on FC.29, FC.31, FC.33, FC.35.
>> 2. do we have a one-off board or do all the armStoneMX8MP-V22I-LIN SBC's have this AIN on board?
>> 3. if all the armStoneMX8MP-V22I-LIN do have AIN on board, is there another armStoneMX8MP variant that does not have the AIN?
<< Part number "armStoneMX8MP-V22I-LIN" do have AIN on board. It is no problem to create a part number with I2C_D option. Please contact our sales office for this purpose.
>> 4. An alternative is to use another I2C, i.e. I2C4 (on pins 8 / 10). Is this I2C available for our use?
<< Sorry, these pins confugured as SPI in part number "armStoneMX8MP-V22I-LIN"! We have to move some jumpers too in this case to use I2C instead of SPI.
What is about I2C_C (FC.19, FC21). These pins seems to have the I2C option not UART_B_RTC/CTS;).