CM3-Panel-7-basic technical documentation
How to manage the I2C buses
On the EXP1 and EXP2 connector of CM3-Panel-7-basic there are two I2C ports available for the user application
| EXP1 pin | Signal | Line |
|---|---|---|
| 11 | I2C SDA1 | GPIO 44 |
| 13 | I2C SCL1 | GPIO 45 |
| 16 | GND |
| EXP2 pin | Signal | Line |
|---|---|---|
| 15 | I2C SDA0 | GPIO 28 |
| 13 | I2C SCL0 | GPIO 29 |
| 16 | GND |
Enable the I2C ports
By default on the CM3-panel-7-basic the I2C bus 1, available on GPIO 44 and 45 lines, is enabled just at Kernel level to comunicate with the touch panel and camera crypto chip.
This is done by modify the standard file config.txt as explained here:
Prepare a microSD card image for CM3-panel-7-basic
The line used in the /boot/config.txt file is this:
dtoverlay=i2c1,pins_44_45
To use the bus at user space level enable the I2C port using
sudo raspi-config
and enable the port by following these options:
Interface Options
I2C
Yes
then reboot.
Install i2c tools to check the I2C bus by typing:
sudo apt update
sudo apt install i2c-tools
Then type:
sudo i2cdetect -l
to see the logical devices to use in out applications
i2c-1 unknown bcm2835 (i2c@7e804000) N/A
i2c-0 i2c i2c-11-mux (chan_id 0) I2C adapter
Type:
sudo i2cdetect -y 0
0 1 2 3 4 5 6 7 8 9 a b c d e f
00: -- -- -- -- -- -- -- -- -- -- -- -- --
10: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
20: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
30: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
40: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
50: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
60: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
70: -- -- -- -- -- -- -- --
and:
sudo i2cdetect -y 0
0 1 2 3 4 5 6 7 8 9 a b c d e f
00: -- -- -- -- -- -- -- -- -- -- -- -- --
10: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
20: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
30: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
40: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
50: -- -- -- -- -- -- -- -- -- -- -- -- -- UU -- --
60: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
70: -- -- -- -- -- -- -- --
to see that just one I2C device is wired on bus I2C-1 that is the Goodix chip used to manage the touch screen panel
Examples
Links
Systems designer, webmaster of www.acmesystems.it and founder of Acme Systems srl
Personal email: tanzilli@acmesystems.it
Web pages: https://www.acmesystems.it --- https://www.acmestudio.it
Github repositories: https://github.com/tanzilli --- https://github.com/acmesystems
Telegram group dedicated to the Acme Systems boards: https://t.me/acmesystemssrl
