You can see, however, that there is no (pull-up) resistor on the pushbutton card. In fact, we can connect such a pull-up resistor by program on the ESP32 GPIO line.

Here is a script that reads the state of the pushbutton switch every 100 ms and prints the result:

from machine import Pin
from time import sleep_ms

pb = Pin(17, Pin.IN, Pin.Pin.PULL_UP)   # set the GPIO line 0 to input and add a pull-up resistor
while True:
     if pb.value() :                    # if we read a high state, the switch is not pressed
           print("Push button is released")
     else:
           print("Push button is pressed")
     sleep_ms(100)

I think we are ready for another exercise session ExerciseSheets#ThirdSession

In the next step, we will read analogue signal levels: AnalogSignals

As you can see, MicroPython supplies a Python module named Pin, which is used to program GPIO pins. In order to control a LED the corresponding pin must be programmed to be an output line.

Running the programs on the PC

python3 name_of_your_program.py

Please give it a try.

Accessing the hardware

The connection of digital input or output signals is made through General Purpose Input Output pins. These pins can be programmed to output (control) a signal level or to input (acquire) a signal level.

The base board and the back of the CPU card look like this (the pins on the ESP32 CPU are mirrored with respect to the base board):

The triple base board	rThe back of the ESP32 CPU board

As you can see, the pins on the triple board are marked

Accessing the user programmable LED

In order to understand how to access GPIO line we must look up the MicroPython documentation. Select Quick reference for the ESP32 and search for Pins and GPIO .

As you can see, MicroPython supplies a Python module named Pin, which is used to program GPIO pins. In order to control a LED the corresponding pin must be programmed to be an output line.

from machine import Pin
from time import sleep
led = Pin(2,Pin.OUT) # the led is connected to GPIO 2 and this is an output line
led.on()             # switches the LED on
sleep(2)             # keeps it on for 2 s
led.off()            # and switches it off again.

Instead of the on() and off() functions, you may also use

led.value(1)         # switches the LED on
led.value(0)         # switches it off

Reading a switch

Hardware access, the General Purpose Input Output (GPIO) pins.

Article text.

-- Uli Raich - 2022-10-15

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