This example shows how to interact with RTL code from Python using switchboard; it's essentially a Python implementation of the minimal example. The Python code sends a switchboard packet containing a number to RTL, which increments the number and sends it back to the Python code in a new switchboard packet. To run the example, type make. You'll see a Verilator build, followed by output like this:
*** TX packet ***
dest: 123456789
last: 1
data: [ 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23
24 25 26 27 28 29 30 31]
*** RX packet ***
dest: 123456789
last: 1
data: [ 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24
25 26 27 28 29 30 31 32]
Looking at the test.py Python code, the outbound switchboard connection is created as an instance of PySbTx, and the outbound packet is sent with PySbTx.send() (defaults to a blocking send). The packet itself is an PySbPacket object. In the testbench.sv RTL code, this packet is received by an instance of the queue_to_sb_sim module, created with the QUEUE_TO_SB_SIM macro from switchboard.vh. The data payload is incremented and assigned to a new switchboard packet, which is transmitted back to Python code with an instance of the sb_to_queue_sim module, created with the SB_TO_QUEUE_SIM macro. The Python code receives that packet via the PySbRx.recv() method (which also defaults to a blocking mode of operation).