Loopback Test

The following steps are provided for the loopback test:

Wiring: Connect Pin19 with Pin 21 as the following:

Figure 1. Connect Pin 19 with 21
Locate to the following path for the test tool, spidev_test.c:
```
cd /linux/tools/spi
```
Execute the following command under the test tool directory:
```
make CROSS_COMPILE=riscv64-linux-gnu- ARCH=riscv
```
Result:
The output file is spidev_test in the same directory.
Upload spidev_test to VisionFive 2, and change the execution permission by executing the following:
```
chmod +x spidev_test
```
Confirm the SPI device.
```
ls /dev/spidev*
```
Result:
Figure 2. Example Output

In this output, spidev1.0 is the device name.
Execute the following command to perform the test:
```
./spidev_test -D /dev/spidev1.0 -v -p string_to_send
```
Tip:
spidev1.0 is the device name got from the previous step.

Result:
Figure 3. Example Output

In this figure, the TX and RX output are the same, which indicates the test is successful.