Basic ADC support for SAMx7x #935
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chris-durand
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| %% if target.family == "e7x/s7x/v7x" | ||
| // values from vendor hal code and application note | ||
| // {{reg}}_MR_TRANSFER(1) is a forbidden value according to the datasheet | ||
| {{reg}}_MR_TRANSFER(1) | |
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I have completely stopped trusting the correctness of the ADC section in the datasheet. It states for the TRACKTIM field:
"Inherent tracking time is always 15 AFE clock cycles. Do not modify this field."
If I follow their guidance and leave TRACKTIM on the reset value of 0, the ADC will read values close to half scale about 50% of the time when its input is connected to GND.
The examples in the app note number 44046 ("Using the Analog Front End in the SAM V7/E7/S7
MCUs") use AFEC_MR_TRACKTIM(2) which according to the text means TRACKTIM + 1 = 3 AFE clock cycles which is not at all equal to 15. That example also has the illegal value of AFEC_MR_TRANSFER(1). Those values are also what the ASF3 vendor HAL has as defaults.
Assuming the app note is right about the meaning of the TRACKTIM field it has to be set to 14 to achieve the recommended tracking time of 15 AFE clock cycles.
There are actually 3 different vendor HAL options offered right now, ASF3, ASF4 and MPLAB Harmony.
ASF4 can only be obtained by registering and downloading a Windows IDE, so I skipped it. The others can be found somewhere on github.
The MPLAB HAL has AFEC_MR_TRANSFER(2) and AFEC_MR_TRACKTIM(15U) which would equate to 16 cycles if the app note was right.
This is all a bit too confusing. I'll go with AFEC_MR_TRACKTIM(14) and the datasheet recommended value of AFEC_MR_TRANSFER(2) until proven otherwise. At least the ADC seems to do the right thing.
chris-durand
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salkinium
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Whoops, forgot about this, sorry! |
Extend basic SAMG55 ADC driver to support SAMx7x devices. The example has been tested in hardware. The peripheral instances follow the naming convention from the datasheet. There the ADC is called
AFEC(analog front-end controller), but it will be provided by themodm:platform:adcmodule for commonality reasons.Tested in hardware.