Mini and Nano -OEM Mesh Rider radios based on the 2023 updated hardware have three GPIOs which can be accessed.
Important notes
- 1. The mini and nano -OEM GPIOs are 0-V to 2.8-V TTL.
- 2. The GPIOs will only be accessible after bootup is complete.
- 3. GPIO0 is logic-level high by default.
Below is an example of how GPIO2 can be used.
1. Prepare GPIO2. Replace "2" with the GPIO number (0, 1, or 2)
echo "2" > /sys/class/gpio/export
2. Set GPIO2 as an output
echo "out" > /sys/class/gpio/gpio2/direction
3. Set the output to high
echo "1" > /sys/class/gpio/gpio2/value
4. Set GPIO2 to low
echo "0" > /sys/class/gpio/gpio2/value
To make GPIO2 an input, use
1. Set GPIO2 as an input
echo "in" > /sys.class/gpio/gpio2/direction
2. Read current GPIO2 status cat /sys/class/gpio/gpio2/value
In hardware versions J and K (OEM only), GPIOs are available for programming through an on-board MCU which is interfaced to the Operating System over USB HID. A program sr-ctrl-usb is pre-installed in the system and is used to access the GPIOs. The general syntax for accessing the MCU is
root@smartradio:~# sr-ctrl-usb <r/w> <param #> <value>
r/w is either 0 for read or 1 for write. The parameter numbers for the three GPIOs are tabulated below. The possible values which can be read or written are 0 and 1 and correspond to 0-V and 3.3-V. Tables 1 and 2 summarize GPIO parameters.
| Param # | Function |
|---|---|
| 6 | Logic level of GPIO1, 0 is GND and 1 is 3.3-V |
| 7 | Logic level of GPIO2, 0 is GND and 1 is 3.3-V |
| 8 | Logic level of GPIO3, 0 is GND and 1 is 3.3-V |
| 11 | Direction of GPIO1, 0 is Output and 1 is Input |
| 12 | Direction of GPIO2, 0 is Output and 1 is Input |
| 13 | Direction of GPIO3, 0 is Output and 1 is Input |
| Param # | Function |
|---|---|
| 5 | Logic level of GPIO1, 0 is GND and 1 is 3.3-V |
| 4 | Direction of GPIO1, 0 is Output and 1 is Input |
As an example, if we want to write a level 1 to GPIO2, we first set the direction of GPIO2 to 0 and then we set the logic level to 1.
root@smartradio:~# sr-ctrl-usb 1 12 0
root@smartradio:~# sr-ctrl-usb 1 7 1
We can read the logic level of GPIO3 with,
root@smartradio:~# sr-ctrl-usb 1 13 1
root@smartradio:~# sr-ctrl-usb 0 8
Note that the GPIO directions are reset to input when the MCU is reset. When the MCU is reset, a reset flag is raised at param # 13 and it should be reset to zero by the user.
For very low power monitoring applications, the Mesh Rider Radio can be configured to completely shut down and wake up on a timer. In order to conserve power, the CPU itself shuts down and it requires around 30 seconds to boot up again. The command to shutdown the system is,
root@smartradio:~# sr-ctrl-usb 1 2 <time in seconds>
where <time in seconds> is the amount of time that the CPU should shut down for. This feature is only available in -J hardware variants.
A simple LED blinking script is available in the Mesh Rider Radio which will cause one of the GPIOs to toggle ON/OFF. This script only applies to Embedded, External, and mini/nano-OEM hardware. Wearable models (-K) have a built-in LED blinking function which works separately. By default, LED blinking is disabled, but it can be enabled by running
root@smartradio:~# uci set led_blink.general.enable='1'
root@smartradio:~# uci commit led_blink
root@smartradio:~# /etc/init.d/startup_blink restart
For mini/nano-OEM models, GPIO0 blinks for single-band radios, and GPIO2 blinks for multiband radios. On External/Embedded radios, GPIOs 1 and 2 can blink. You can see a full list of configuration parameters by running
root@smartradio:~# uci show led_blink
led_blink.general=led_blink
led_blink.general.inactive_thres='1000'
led_blink.general.blink_rate='0.3'
led_blink.general.gpio_selected='2'
led_blink.general.enable='0'
The blink_rate is measured in seconds, and the inactive_threshold is the time since hearing from another station, after which the LED will start to blink.