I know the ARM chip used in the Photon has 3 ADCs. Are they connected to specific pins or do the ADCs get allocated by the chip using some other algorithm.
I want to make sure that when I use the different Analog pins on the Photon, they are handled by the same internal ADC, how do I ensure that?
Look under here: https://docs.particle.io/datasheets/photon-datasheet/#pin-description
It tells you which are analog pins (basically A0-A7).
Looking at the data sheet:
A7 - PA0 - ADC123_IN0
A6 - PA4 - ADC12_IN4
A5 - PA7 - ADC12_IN7
A4 - PA6 - ADC12_IN6
A3 - PA5 - ADC12_IN5
A2 - PC2 - ADC123_IN12
A1 - PC3 - ADC123_IN13
A0 - PC5 - ADC12_IN15
@BDub should be able to share more from the information.
What’s the reason for wanted to use the same ADC?
Sorry I want to know that at a precise moment in time I can fire off all 3 ADCs on 3 different Analogu pins.
So from the information above it seems like some pins won’t have access to the 3rd ADC of the ARM chip. Is that correct?
I was looking for something like that, and couldn’t find it. Is it
https://docs.particle.io/assets/images/photon-pinout2.png that you’re looking at? If so, how do you infer which ADC serves which pins?
If I’m interpreting what you wrote correctly, there are two ADCs: ADC12 and ADC123.
ADC12 can multiplex between A0, A3, A4, A5 & A6
ADC123 can multiplex between A1, A2 & A7
There are actually 3 ADC’s:
3 × 12-bit, 0.5 μs ADCs with up to 24 channels and up to 6 MSPS in triple interleaved mode
And if a pin is labeled as ADC123_IN12, that means it can be accessed as channel 12 on ADC 1, 2, or 3.
Checkout the datasheet: STM32F205xx (STM32F205RGY6) and reference manual RM0033 
Have a look here (MODULE worksheet)
https://github.com/spark/photon/blob/master/pin-mapping/photon-pinmap.xlsx
Or you look at the STM32F2xx datasheet and match up the GPIO pins
But doesn’t this still mean that if I wanted to sample using all 3 ADCs at exactly the same time then I am restricted to which pins I can use because most inputs cannot use ADC3 except A1,2,7?
