https://github.com/matthias-bs/micropython-adc_cal

MicroPython ESP32 library for calibrated on-chip ADC conversion
https://github.com/matthias-bs/micropython-adc_cal

esp32 micropython micropython-esp32

Last synced: about 1 month ago
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MicroPython ESP32 library for calibrated on-chip ADC conversion

• Host: GitHub
• URL: https://github.com/matthias-bs/micropython-adc_cal
• Owner: matthias-bs
• Created: 2021-05-10T20:54:51.000Z (over 3 years ago)
• Default Branch: main
• Last Pushed: 2023-02-07T09:16:16.000Z (almost 2 years ago)
• Last Synced: 2024-11-02T07:20:27.614Z (about 2 months ago)
• Topics: esp32, micropython, micropython-esp32
• Language: Python
• Homepage:
• Size: 136 KB
• Stars: 18
• Watchers: 1
• Forks: 1
• Open Issues: 0
• Metadata Files:
  • Readme: README.md

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# MicroPython-ADC_Cal

**MicroPython ESP32 library for calibrated on-chip ADC conversion**

***Please refer to ESP32 documentation for maximum ADC input voltage ratings!!!***

The [Espressif IDF API Reference](https://docs.espressif.com/projects/esp-idf/en/latest/esp32/api-reference/peripherals/adc.html) describes the limitations of the ESP32's built-in analog-to-digital converter - and provides a (partial) solution in terms of providing a method for improving its accuracy by using a chip specific calibration value (or two calibration values, respectively) stored in the efuse. It also provides useful information regarding *noise mitigation* and the *suggested range* of input voltages in each mode.

This [ADC calibration scheme](https://github.com/espressif/esp-idf/blob/master/components/esp_adc_cal/esp_adc_cal_esp32.c) is (in parts) provided by the ADC1Cal class.

The following restriction applies:

* Only V_ref calibration mode is supported
(This is due to the fact that the author does not have a proper ESP32 device to test two point calibration mode.)

`ADC1Cal` extends MicroPython's ESP32 `machine.ADC` class. Please refer to the [MicroPython ESP32 ADC documentation](https://docs.micropython.org/en/latest/esp32/quickref.html#adc-analog-to-digital-conversion) for methods and attributes inherited from the `ADC` class.

    Attributes:

        name (string):      instance name (for debugging)

        vref (int):         ADC reference voltage in mV (from efuse calibration data or supplied by programmer)

    Methods:

        @property

        voltage()

            Get voltage measurement [mV]

            Returns:

                float: voltage [mV]

        

        __str__()

            Dump object info as a string

            

            Returns:

                string: "Name:   width: , attenuation: , raw value: , value: "


**Usage example:**

        from machine import Pin

        import adc1_cal

        

        ADC_PIN   = 35                # ADC input pin no.

        DIV       = 1                 # div = V_measured / V_input; here: no input divider

        AVERAGING = 10                # no. of samples for averaging (default: 10)

        

        # vref = None -> V_ref calibration value is read from efuse

        ubatt = ADC1Cal(Pin(ADC_PIN, Pin.IN), DIV, None, AVERAGING, "ADC1 Calibrated")

        

        # set ADC result width

        ubatt.width(ADC.WIDTH_10BIT)

    

        # set attenuation

        ubatt.atten(ADC.ATTN_6DB)

    

        print('ADC Vref: {:4}mV'.format(ubatt.vref))

    

        print('Voltage:  {:4.1f}mV'.format(ubatt.voltage))