SolutionsToADCAndDAC < IoT_Course

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---+ Solutions to exercise 9: ADC and DAC
---++ Exercise 1:

As you can see on the photo, the joystick has 5 pins:
| *Pin on Joystick* | *Pin on ESP32* |
| GND | GND |
| 5V | 3.3V |
| URx | GPIO 34 |
| URy | GPIO 33 |
| SW | Switch, can be connected to any GPIO<br />not used for the eercise |
GPIO 33 and 34 are located on the second row of the WROVER CPU card and not connected to the !WeMos bus.

<img alt="joystick.png" src="%ATTACHURL%/joystick.png" title="joystick.png" />

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:

<verbatim>ampy mkdir /lib
ampy put ads1x15 /lib/ads1x15</verbatim>

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

<verbatim>from ad1x15 import ADS1115</verbatim>

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.

-- %USERSIG{UliRaich - 2021-02-06}%

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Topic revision: r1 - 2021-02-06 - UliRaich