umi_fifo_flex is a module from the UMI repository that serves as an adapter between SUMI interfaces with different data widths. For example, it can split up SUMI packets with wide data payloads to send them through a SUMI interface with a narrow data bus. This example shows how to use switchboard to implement a loopback test through umi_fifo_flex to verify its operation. It's conceptually similar to the umi_fifo example, but the required test logic is more complex, since it is not enough to directly compare the output stream of packets to the input stream, due to the fact that umi_fifo_flex may split and merge UMI packets. Instead, we need to check that the output stream has the same meaning as the input stream.
Because this is a common pattern, we provide a library function for performing a loopback test, umi_loopback(). The function accepts two main arguments: a UmiTxRx connection, and the number of SUMI packets to send into the DUT. As you can see in test.py, this allows for a loopback test to be implemented more concisely than in the umi_fifo example.
Assuming that switchboard is installed in your current Python environment, you can run the example with ./test.py. The output will look like this:
100%|████████████████████████████████████████████████████████████████| 3/3 [00:00<00:00, 29.11it/s]
The 3/3 output indicates that three packets were sent into the DUT. You can change the number of packets sent with -n NEW_VALUE, e.g. ./test.py -n 100. We also suggest using the --fast flag to avoid rebuilding the simulator once it has already been built.