This tutorial will show how to configure and use the ESP32 touch sensors.
The ESP32 touch sensor detects variations in capacitance on the GPIO pins, thus detecting touch or proximity.
We assume that you have set up your development environment as described in the IDE tutorial.
We also assume that you have flashed your device with Jaguar and that you are familiar with running Toit programs on it. If not, have a look at the Hello world tutorial.
The ESP32 has 10 pins that can be used as touch sensors: 0, 2, 4, 12-15, 27, 32-33. In this tutorial we will use pin 32.
Simply connect a male-male (jumper) wire to pin 32, and leave the other end unconnected. We will use the unconnected end as a touch sensor.
Create a new file
touch.toit and start
jag watch touch.toit to
run the program whenever you save.
import gpio import gpio.touch as gpio main: pin := gpio.Pin 32 touch := gpio.Touch pin while true: print (touch.read --raw) sleep --ms=500
This program will print the raw value of the touch sensor every 500ms. Typically, the raw value will be around 1000-1200 when the wire is left untouched and decreases to around 200 when touched with a finger.
Take a value that is in the seen range (for example 800) and use it in the following program as threshold.
import gpio import gpio.touch as gpio main: pin := gpio.Pin 32 touch := gpio.Touch pin touch.threshold = 800 while true: is_touched := touch.get print (is_touched ? "touched" : "not touched") sleep --ms=500
The program will now print
touched when the wire is touched and
not touched when it is not touched. Compared to just looking at the
raw value, there isn't a huge advantage in using the
in this example. However, the same
threshold is also used when
a touch pin is used to wake up from deep sleep.
Often the calibration value (here 800) will be determined during production and stored in the device's flash memory. You can also do this calibration dynamically:
import gpio import gpio.touch as gpio ITERATIONS := 100 calibrate touch/gpio.Touch: sum := 0 ITERATIONS.repeat: sum += touch.read --raw // Use 4/5th of the average as cutoff. threshold := (sum * 4) / (5 * ITERATIONS) print "Threshold: $threshold" touch.threshold = threshold main: pin := gpio.Pin 32 touch := gpio.Touch pin calibrate touch while true: is_touched := touch.get print (is_touched ? "touched" : "not touched") sleep --ms=500
It's important that the wire is not touched during the calibration phase.