spi.rst

SPI via Greybus

After running gbridge, if the board in use exposes SPI via Greybus, and the user has run modprobe spidev, then the Linux kernel will create /dev/spidevN.N entries for you.

Just to make sure that we're interacting with the Greybus SPI device, run the following (reading and writing to random I2C devices can sometimes have negative consequences).

ls -la /sys/bus/spi/devices/* | grep "greybus"
lrwxrwxrwx 1 root root 0 Dec 11 15:01 /sys/bus/spi/devices/spi0.0 -> ../../../devices/virtual/gb_netlink/gb_netlink/greybus1/1-2/1-2.2/1-2.2.3/gbphy1/spi_master/spi0/spi0.0

In this case, we will read values a sensor on the cc1352r_sensortag.

Since we don't yet have generic userspace SPI tools like we do for I2C, a small application was written specifically to read this sensor.

The source code for the application can be found here.

To clone and build the application, simply run the following:

git clone https://github.com/cfriedt/cc1352r-sensortag-adxl362-greybus-demo.git adxl362
cd adxl362
make -j$(nproc --all)

Next, we will stream accelerometer values from the adxl362.

sudo ./adxl362
(x,y,z,°C) =   -0.823758,   0.147099,  11.169774, -28.990000
(x,y,z,°C) =   -0.823758,   0.147099,  11.169774, -28.990000
(x,y,z,°C) =   -0.804145,   0.156906,  11.140354, -28.990000