Solutions to exercise 9: ADC and DAC

Exercise 1:

As you can see on the photo, the joystick has 5 pins:

Creating an instance from the ADC class in the machine module is simple as is reading from it. See http://docs.micropython.org/en/latest/esp32/quickref.html

Exercise 2:

Connect the ESP32 DAC output to the input of the ADC (DAC: GPIO 26, ADC: GPIO 36). Ramp the DAC data, starting from 0 to its max value: 255 in steps of one. Wait for 50ms to be sure the DAC output has settled. Then read the ADC and write the result to a file in ascii format. You can use gnuplot to easily visualize the results.

Exercise 3:

For once the driver of the ads1115 ADC is not already included in the MicroPython binary. Before using it, it must be uploaded to the ESP32 flash:

ampy mkdir /lib
ampy put ads1x15 /lib/ads1x15

The first command is only needed if /lib does not exist already on the ESP32. Now we can

from ad1x15 import ADS1115

and use it.

The program is essentially the same as the one in exercise 2.

Exercise 4:

Explained on the TWiki page ADC and DAC

Exercise 5:

For the exercises an oscilloscope is needed.We have a very cheap Hantek USB oscilloscope in our lab equipment. Connect one of the probes to the output of the DAC ( GPIO 26) and observe the result of your programs on the scope display. ADC and DAC has screen dumps of what you are expected to see.

-- Uli Raich - 2021-02-06

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