Add MIDI loopback test and fix app_midi_simple Tx

tests/test_midi_loopback.py

@@ -0,0 +1,60 @@
+# Copyright 2014-2024 XMOS LIMITED.
+# This Software is subject to the terms of the XMOS Public Licence: Version 1.
+
+import pytest
+import Pyxsim
+from Pyxsim import testers
+from pathlib import Path
+from uart_rx_checker import UARTRxChecker
+from midi_test_helpers import midi_expect_rx, create_midi_rx_file, create_midi_tx_file, tempdir, MIDI_RATE
+from distutils.dir_util import copy_tree # we're using python 3.7 and dirs_exist_ok=True isn't available until 3.8 :(
+
+MAX_CYCLES = 15000000
+
+
+#####
+# This test takes the built binary, copies it to a tmp dir and runs the midi loopback test which sends some commands
+# the firmware receives them, prints and compares with the expected output
+#####
+def test_midi_loopback(capfd, build_midi):
+    # Need tempdir as we use the same config files and this causes issues when using xdist 
+    with tempdir() as tmpdirname:
+        config = "LOOPBACK"
+        copy_tree(build_midi, tmpdirname)
+        xe = str(Path(tmpdirname) / f"{config}/test_midi_{config}.xe")
+
+        midi_commands = [
+                        [0x90, 60, 81], #note on
+                        [0xc0, 15],     #instr select
+                        [0xe0, 0, 96],  #pitch bend 
+                        [0xff],         #MIDI reset
+                        [0x80, 60, 81], #note off
+                        ]
+        create_midi_rx_file(len(midi_commands))
+        create_midi_tx_file(midi_commands)
+
+        expected = midi_expect_rx().expect(midi_commands)
+        tester = testers.ComparisonTester(expected, ordered = True)
+
+        simthreads = []
+
+        simargs = ["--max-cycles", str(MAX_CYCLES)]
+        #This is just for local debug so we can capture the traces if needed. It slows xsim down so not needed
+        # simargs.extend(["--trace-to", "trace.txt", "--vcd-tracing", "-tile tile[1] -ports -o trace.vcd"]) 
+
+        Pyxsim.run_with_pyxsim(
+            xe,
+            simthreads=simthreads,
+            timeout=120,
+            simargs=simargs,   
+        )
+        capture = capfd.readouterr().out
+        result = tester.run(capture.split("\n"))
+
+        # Print to console
+        # with capfd.disabled():
+        #     print("++++", capture, "++++")
+        #     print("----", expected, "----")
+
+
+        assert result