What is the best way (in Python) to convert 32-bit signed longs to 7-bit ints, in order to transmit them via Firmata/serial link? Converting into 8-bit is not a problem, just (long_val).to_bytes(4, 'little'). The final sequence should be like this:
No 1, bits 0-6
No 2, bits 7-13
No 3, bits 14-20
No 4, bits 21-27
No 5, bits 28-32
A backward conversion from a 5-item sequence of 7-bit ints into 32 bit signed longs would also be very helpful.
s = bin(pos)[2:].zfill(32)
cmd = bytearray([acc.ACCELSTEPPER_TO, dev_no,
int(s[28:32], 2), int(s[21:28], 2), int(s[14:21], 2),
int(s[7:14], 2), int(s[0:7], 2)])
brd.send_sysex(acc.ACCELSTEPPER_DATA, cmd)
My methods unfortunately produced wrong result, so I would like to discard them completely and restart from scratch. Thanks in advance for any suggestion(s).
Just do the conversions 7 bits at a time:
bytes = []
for i in range(5):
bytes.append(long_value & 0x7f)
long_value >>= 7
long_value = 0
for i in reversed(range(5)):
long_value <<= 7
long_value |= bytes[i]