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Bug #1066: Add helper function to send SysEx/MTC via usb-device-midi #1068

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Bug #1066: Add helper function to send SysEx/MTC via usb-device-midi #1068

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59 changes: 59 additions & 0 deletions micropython/usb/usb-device-midi/usb/device/midi.py
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Original file line number Diff line number Diff line change
Expand Up @@ -108,6 +108,65 @@ def note_off(self, channel, pitch, vel=0x40):
def control_change(self, channel, controller, value):
self.send_event(_CIN_CONTROL_CHANGE, _MIDI_CONTROL_CHANGE | channel, controller, value)

def send_sysex(self, p):

@dpgeorge dpgeorge Jul 1, 2026

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There is a lot of duplicated code in this function. Do you think you can factor it to be simpler? For example:

def send_sysex(self, p):
    while p:
        w = self._tx.pend_write()
        if len(w) < 4:
           return False
        if len(p) > 3:
            w[0] = _CIN_SYSEX_START
            ...
        elif len(p) > 2:
            w[0] = _CIN_SYSEX_END_3BYTE
            ...
        elif len(p) > 1:
            ...
        else:
            w[0] = _CIN_SYSEX_END_1BYTE
        self._tx.finish_write(4)
        self._tx_xfer()

(And what's supposed to happen for when len(p) is greater than 7?)

if len(p) > 3:
w = self._tx.pend_write()
if len(w) < 4:
return False # TX buffer is full. TODO: block here?

w[0] = _CIN_SYSEX_START
w[1] = p[0]
w[2] = p[1]
w[3] = p[2]
self._tx.finish_write(4)
self._tx_xfer()

p = p[3:]

# play out til end
while p:
if len(p) > 2:
w = self._tx.pend_write()
if len(w) < 4:
return False # TX buffer is full. TODO: block here?

w[0] = _CIN_SYSEX_END_3BYTE
w[1] = p[0]
w[2] = p[1]
w[3] = p[2]
self._tx.finish_write(4)
self._tx_xfer()

p = p[3:]
elif len(p) > 1:
w = self._tx.pend_write()
if len(w) < 4:
return False # TX buffer is full. TODO: block here?

w[0] = _CIN_SYSEX_END_2BYTE
w[1] = p[0]
w[2] = p[1]
w[3] = 0
self._tx.finish_write(4)
self._tx_xfer()

p = p[2:]
else:
w = self._tx.pend_write()
if len(w) < 4:
return False # TX buffer is full. TODO: block here?

w[0] = _CIN_SYSEX_END_1BYTE
w[1] = p[0]
w[2] = 0
w[3] = 0
self._tx.finish_write(4)
self._tx_xfer()

p = p[1:]

return True

def send_event(self, cin, midi0, midi1=0, midi2=0):
# Queue a MIDI Event Packet to send to the host.
#
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