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OLIMEX© 2015
A20-OLinuXino-MICRO user's manual
2.8.1 Android calibration
Calibrating a display under Android is pretty straightforward from the Android application.
Important: initially the boards are calibrated for a specific display and resolution. If you re-write the
image (no matter whether the SD card or the NAND memory) you might need to use a mouse to
calibrate the display initially. It might be impossible to calibrate it only by using the touch
component over the display.
2.8.2 Debian calibration
The command that allows calibrating in Debian Linux is:
ts_calibrate
The default Debian setup is made with settings for HDMI 720p/60Hz. If you want to change some
other LCD, VGA or HDMI resolution then you have to start script file in /root directory.
If the problem is under Debian Linux make sure you are properly logged in the LXDE interface!
Else applying calibration would not happen for the current user – if you are calibrating from the X
graphical interface make sure that you are logged as user "olimex" (if calibrating without the X, the
user is "root").
#su olimex
enter the password: olimex
calibrate the touch screen and reboot the board
#sudo reboot
2.9 GPIO under Debian
You can read data from a given GPIO port. The logical ranges are usually as follows:
0V-1V for LOW (or 0)
2.4V-3.3V for HIGH (or 1)
All voltages are measured against ground (GND).
If the input signal is to high, you will at least destroy the port!
The algorithms for writing a value to a GPIO port and reading such a value are pretty similar. The
usage of GPIO ports follows the algorithm (we would use GPIO #49 for demonstration purposes):
1. Export GPIO 49:
echo 49 > /sys/class/gpio/export
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