From datasheet -
soc – Input *
The start of conversion (soc) is an optional pin. You see it if you select the Hardware Trigger
sample mode. A rising edge on this input starts an ADC conversion. If this input is high when the
SAR_Start() function is called, a conversion will start immediately. After the first conversion, a
rising edge on the input will start an ADC conversion. This signal should be synchronized to the
ADC_SAR clock. If you set the Sample Mode parameter to Free Running, this I/O is hidden.
Seems to say if I select HW trigger SOC will show, otherwise hidden. But then it says its only
hidden if I select free running. Below I set to SW trigger, and SOC is showing ?
The description of when this pin is shown or hidden is incorrect. The intention is to show this pin unless you are in the Free Running mode, so the statement at the bottom of the paragraph is correct. That brings up the issue of what does it do in the case of Software Trigger mode and what should you do with the pin. I'll describe the 3 modes here:
- Free Running: SOC is not present.
- Hardware Trigger: SOC is present and is the trigger to start conversions.
- Software Trigger: SOC is present. If you only want to do software based conversions, then you can leave this pin unconnected (it is connected to a 0 by default) or if you would prefer to have all the inputs with explicit connections (my preference) then you can connect a constant 0. If you want to use a mix of hardware and software triggered operation, then this is the setting to use. In this case you can use hardware triggering until you make the first call to StartConvert(). At that point the SOC pin is disabled and conversions are triggered only by software by making more calls to StartConvert(). If you want to use hardware triggering again it is enabled by StopConvert(). You can see that StartConvert() and StopConvert() have the side effect that they switch on and off whether hardware triggering is active.