SAR ADC digitize negative side of differential input...

[JaLi_1091341]

Hello pSoc4 Gurus,

I have a sensor which provides a differential output where one signal is essentially the reference level and the other is the signal.    Interfaced to a differential channel of the pSoc4 SAR ADC component everything works as it should.    Basically ...

Sensor Signal ----> SAR ADC Positive input of ch0

Sensor Reference ----> SAR ADC negative input of ch0

I would like to determine if a sensor is connected or not.   One way to do this would be to measure the voltage on the Sensor reference channel.    I have tried to do this in various ways but always get an analog routing error while build the project.    It appears that the same input pin cannot be connected to both the negative input of ch0(differential) and ch7(single ended with negative at Vss).

Any suggestions appreciated.

Thanks

Jim

[odissey1 · Accepted solution]

I would try analog Mux at the input configured as DPDT (double pole double throw), connected to ADC_SAR differential input. Input 0 is connected to sensor high output, and input 2 is connected to sensor low output. Input 1 is connected to the ground and input 3 to sensor low. The ADC is always in differential mode.

For signal measurement inputs 0 and 2 provide differential path to ADC input. For sensor presence testing, the Mux is switched to inputs 1 and 3. ADC will return ''negative" voltage, but that is correctable in software.

/odissey1