GPIOs
| PIN | Beta | Mk I |
|---|---|---|
| 1 | Ground | Ground |
| 2 | USB 5V | USB 5V |
| 3 | GPIO5[27] (CSI0_DAT9) | GPIO5[26] (CSI0_DAT8) |
| 4 | UART1_TX / GPIO5[28] (CSI0_DAT10) | GPIO5[27] (CSI0_DAT9) |
| 5 | UART1_RX / GPIO5[29] (CSI0_DAT11) | UART1_TX / GPIO5[28] (CSI0_DAT10) |
| 6 | GPIO5[30] (CSI0_DAT12) | UART1_RX / GPIO5[29] (CSI0_DAT11) |
| 7 | GPIO5[31] (CSI0_DAT13) | GPIO5[30] (CSI0_DAT12) |
The breakout header can be accessed, among other options, with a solderless header such as this one or this one (346-87-107-41-036101).
The serial port can be connected to via a USB to TTL cable.
The header can also be used to route I²C (Inter-Integrated Circuit) and SPI (Serial Peripheral Interface) interfaces.
When using Linux the 5 GPIOs, exposed on the breakout header (pins 2-7), are easily configurable using the GPIO Sysfs interface.
The following example shows how to set bit 30 of the i.MX53 GPIO5 interface, corresponding to pin 7, in output mode and write 1 and 0 from a Linux shell.
# echo 158 > /sys/class/gpio/export # 128 (GPIO5[0]) + 30 = GPIO5[30]
# echo out > /sys/class/gpio/gpio158/direction
# echo 1 > /sys/class/gpio/gpio158/value
# echo 0 > /sys/class/gpio/gpio158/value
The Mk I LED can be controlled in different ways depending on your Linux kernel and Device Tree (dts) configuration. The following examples shows usage on default Debian and Arch Linux images.
Debian examples:
## unload the default LED modules
# modprobe -r leds_gpio led_class ledtrig_heartbeat
# echo 123 > /sys/class/gpio/export # 96 (GPIO4[27]) + 27 == GPIO4[27]
## full brightness
# echo out > /sys/class/gpio/gpio123/direction
# echo 0 > /sys/class/gpio/gpio123/value # LED on
# echo 1 > /sys/class/gpio/gpio123/value # LED off
## mid-brightness trick
# echo in > /sys/class/gpio/gpio123/direction
To permanently disable the default LED usage comment the ledtrig_heartbeat line from /etc/modules and blacklist leds_gpio and led_class:
sed -i /etc/modules -e 's/ledtrig_heartbeat/#ledtrig_heartbeat/'
echo -e "blacklist leds_gpio\nblacklist led_class" > /etc/modprobe.d/led-blacklist.conf
Arch Linux examples:
## trigger on USB activity
# echo usb-gadget > /sys/devices/platform/leds/leds/LED/trigger
## trigger on microSD activity
# echo mmc0 > /sys/devices/platform/leds/leds/LED/trigger
## disable trigger
# echo none > /sys/devices/platform/leds/leds/LED/trigger
# LED on
# echo 1 > /sys/devices/platform/leds/leds/LED/brightness
# LED off
# echo 0 > /sys/devices/platform/leds/leds/LED/brightness