"resource not available" when assigning P9 / G16 as ADC

[soren]

Hello,

After much headache I discovered this post (https://forum.pycom.io/topic/313/lopy-pin-out/3)
where one user says that it's possible to find the correlation between chip pins and expansion board pins with a REPL command.
And so I found out that P9 on the chip is G16 on the expansion board and this pin should have ADC capability.

So I wrote in my code:

adc = machine.ADC()
sensorPin = adc.channel(pin="P9")

But it keeps throwing a "OSError: resource not available" on that second line. I did import machine.

What is this supposed to mean? That P9 is not G16 after all, or despite this diagram (https://docs.pycom.io/chapter/datasheets/downloads/lopy-pinout.pdf) saying that P9 has ADC, it does not? Or that some other feature on this port prevents me from using it?

EDIT: after making sure I wasn't using ADC2 ( the ones on the left side), I got rid of this error for some time. Now it's come back, and it doesn't matter which pin I use: ADC is just not available as a resource, and I'm getting no clue what so ever as to why this is..

[jmarcelino]

@soren
The ADC2 pins are not available from Python, at least for the time being. You can only use ones starting with ADC1_...

[soren]

@jmarcelino thank you very much for chiming in. i'm baffled why this isn't stated in capital letters on the official pinout diagrams

[soren]

@jmarcelino so now I'm also getting this error from ADC1 pins... P14, to be precise

[robert-hh]

@soren Are sou sure? I can do it here.

import machine
adc = machine.ADC()
sensorPin = adc.channel(pin="P14")

[soren]

@robert-hh

Hi robert, as far as I can tell - I'm doing the same thing as you.. here is my code, it's on line 9 ("sensorPin = adc...) it reports this error:

import machine 
from machine import Pin
import time
import pycom
from machine import ADC
from machine import PWM

adc = machine.ADC()
sensorPin = adc.channel(pin='P23', attn=ADC.ATTN_11DB) # G4 on expansion board
ledArray = [0x7f0000, 0x007f00, 0x0000ff] # red, green, blue
step_p = Pin('P8', mode=Pin.OUT)
stepDir_p = Pin('P21', mode=Pin.OUT)


class ColorSensor:

    dosingPump_p = Pin('P21', mode=Pin.OUT)
    dosingPump_p.value(0)
    # SERVO:
    pwm = PWM(0, frequency=50)
    servo_p = pwm.channel(0, pin='P22', duty_cycle=0.127)
    servo_p.duty_cycle(0.107)
    # 0.107 # upright position
    # 0.03 # pouring position

    balanceSet = False
    colourArray = [0, 0, 0]
    whiteArray = [0, 0, 0]
    blackArray = [0, 0, 0]
    avgRead = 0

    def checkBalance(self):
        print("checking balance")
        if not self.balanceSet:
            self.setBalance()

    def setBalance(self):
        print("setting balance")
        time.sleep(5)
        for num in range(0, 3): # set white bal
            print(num)
            pycom.rgbled(ledArray[num]) # set to color
            time.sleep(0.1)
            self.getReadings(5)
            self.whiteArray[num] = self.avgRead
            print('avgRead from bal ', self.avgRead)
            pycom.rgbled(0x000000) # turn off led
            time.sleep(0.1)
        time.sleep(5)
        for num in range(0, 3): # set black bal
            pycom.rgbled(ledArray[num])
            time.sleep(0.1)
            self.getReadings(5)
            self.blackArray[num] = self.avgRead
            pycom.rgbled(0x000000) # turn off led
            time.sleep(0.1)
        self.balanceSet = True
        time.sleep(5)


    def checkColour(self):
        print("rinsing...")
        for num in range(0, 3): # rinse glass 3 times
            dosingPump_p.value(1) # take in water from aquarium
            time.sleep_ms(500) # how much water to take in?
            dosingPump_p.value(0) # turn off dosing pump
            time.sleep(1)
            servo_p.duty_cycle(0.03) # pour out water
            time.sleep(4)
            servo_p.duty_cycle(0.107) # turn back glass
            time.sleep(4)
        print('rinsing finished! Taking in water...')
        dosingPump_p.value(1) # take in water from aquarium
        time.sleep_ms(500) # how much water to take in?
        dosingPump_p.value(0) # turn off dosing pump
        time.sleep(1)

        print('taking plunger down...')
        for num in range(0, 201): # take plunger down
            step_p.value(1)
            time.sleep_ms(500)
            step_p.value(0)
            time.sleep_ms(500)
            # check if plunger is all the way down and break ?
        print('plunger is down! Waiting for analysis...')

        time.sleep(1) # set to 3 minutes
        print('analysis ready! Reading colours...')

        for num in range(0, 3):
            pycom.rgbled(ledArray[num]) # set to color
            time.sleep(0.1)
            self.getReadings(5)
            self.colourArray[num] = self.avgRead
            print('whitearray ', self.whiteArray[num], ' blackArray ', self.blackArray[num])
            greyDiff = self.whiteArray[num] - self.blackArray[num]
            print('greydiff: ', greyDiff)
            self.colourArray[num] = (self.colourArray[num] - self.blackArray[num])/(greyDiff)*255
            pycom.rgbled(0x000000) # turn off led
            time.sleep(0.1)

    def printColour(self):
        print('printing colour')
        return self.colourArray[0], self.colourArray[1], self.colourArray[2]

    def getReadings(self, times):
        reading = 0
        tally = 0
        for num in range(0, times+1):
            reading = sensorPin()
            print('reading ', reading)
            tally = reading + tally
            time.sleep(0.01)
        self.avgRead = (tally)/times
        print('avgRead ', self.avgRead)
        #print('avgRead ', avgRead)

[robert-hh]

@soren P23 belongs to ADC2 ..... You should write P14, or G4, like you state in the comment

[soren]

@robert-hh yes, sorry i know - I have been trying with the following pins with that code i send you now: "13, 14, 15 and 23". 13, 14 and 15 is adc1.

I think maybe I understand the problem a tiny bit better now:
it happens only when I'm doing a soft reset. When I do a hard reset, it works again. Is this because a soft reset doesn't free up the pins maybe?

[HenroRitchie]

@jmarcelino Is this still the case. I am trying to access ADC2 on a Lopy4 and get the same error OSError: resource not available. ADC1 seems to be working fine.

[jmarcelino]

@HenroRitchie
I've not followed the Pycom developments too closely but at low level ADC2 is only available when WiFi is off "ADC2 is used by the Wi-Fi driver. Therefore the application can only use ADC2 when the Wi-Fi driver has not started."

My guess is this complicates things in a dynamic Python environment where you can turn WiFi on and off at will so probably not a priority.

To be honest ADC1 is quite noisy so I avoid the ESP32 ADCs altogether and now use a more "industrial grade" external solution.

[HenroRitchie]

@jmarcelino Thank you, noted. Will design accordingly.

[robert-hh]

@jmarcelino Hello Jose. Are you back again?

[jmarcelino]

@robert-hh
Hey Robert! Good to see you're still around. Not back at Pycom but some collaboration brewing up, watch this space ;-)