Add getTemperature() to support internal temp sensor

[nseidle]

This PR:

• Adds a getTemperature() function. If there's a better func name, let me know. I did some googling for other platforms and didn't find any clear precident.

Function is wholly based on adc_vbatt.c example from latest Ambiq SDK. Function is required (rather than a ADC read and a series of maths) because there's a HAL call that reads the on board calibration factors. It was easier to leverage their call then roll our own.

uint32_t ui32Retval = am_hal_adc_control(g_ADCHandle, AM_HAL_ADC_REQ_TEMP_CELSIUS_GET, fVT);

getTemperature correctly pulls in user's chosen analogResolution() with a pow(2, _analogBits) calculation.

[stephenf7072]

I've tried this branch, seems all good. getTemperature() returns believable values at room temperature and under hot air at nominally 100degC.

[oclyke]

Code looks good! We're test-driving the new (more formal) process of merging PRs into the 'release-candidate' branch. @nseidle can you adjust this PR to target that branch?

I'm not sure if there is an easy way or if you will have to close this PR and open a new one targeting the correct branch. Let me know if you run into trouble since this is a pretty new process for us!

[nseidle]

Changed target branch (not too hard).

[oclyke]

Awesome. I'm glad it was easy for you. I wonder if that had to do with your access level? PaulZC had trouble with the same task here

[oclyke]

While doing my final review I had one thought about the name of this function. Other than that it seems good and others report that it tests well (I loaned my hardware to Kyle last week and have yet to retrieve it)

[oclyke]

I feel like getTemperature() is just a bit too generic. What am I getting the temperature of? Should I be passing in an argument that is a value to convert to temperature?

How about something like getInternalTempC() or getChipTempC()?

[nseidle]

I'm all for a name change. getInternalTemp() is better IMO. Want me to make the changes?