esp8266 micropython plant sensor and vcc

main.py

import esp
from flashbdev import bdev
import machine

# https://github.com/micropython/micropython/issues/2352
ADC_MODE_VCC = 255
ADC_MODE_ADC = 0

def set_adc_mode(mode):
    sector_size = bdev.SEC_SIZE
    flash_size = esp.flash_size() # device dependent
    init_sector = int(flash_size / sector_size - 4)
    data = bytearray(esp.flash_read(init_sector * sector_size, sector_size))
    if data[107] == mode:
        return  # flash is already correct; nothing to do
    else:
        data[107] = mode  # re-write flash
        esp.flash_erase(init_sector)
        esp.flash_write(init_sector * sector_size, data)
        print("ADC mode changed in flash; restart to use it!")
        return

def get_adc_mode():
    sector_size = bdev.SEC_SIZE
    flash_size = esp.flash_size() # device dependent
    init_sector = int(flash_size / sector_size - 4)
    data = bytearray(esp.flash_read(init_sector * sector_size, sector_size))
    return data[107]


import urequests
import time

if get_adc_mode() == ADC_MODE_VCC:
    vcc = machine.ADC(1)
    val = vcc.read()
    time.sleep(2)
    val = vcc.read()
    payload = "plant_vcc,plant=%d value=%f\n" % (0, val)
    set_adc_mode(ADC_MODE_ADC)
else:
    a0 = machine.ADC(0)
    a0.read()
    time.sleep(2)
    val = a0.read()
    payload = "plant_hum,plant=%d value=%d\n" % (0, val)
    set_adc_mode(ADC_MODE_VCC)

url = 'host'
headers = {'authorization': "Basic ...",'cache-control': "no-cache"}
resp = urequests.post(url, data=payload, headers=headers)

time.sleep(10)

# configure RTC.ALARM0 to be able to wake the device
rtc = machine.RTC()
rtc.irq(trigger=rtc.ALARM0, wake=machine.DEEPSLEEP)

# set RTC.ALARM0 to fire after 7 min (waking the device)
rtc.alarm(rtc.ALARM0, 420000)

# put the device to sleep
machine.deepsleep()