==== TEST rx callbacks ====
cb0
pending
cb0
full
cb0a
overflow
cb1
pending
cb1
full
cb1a
overflow
[1, False, False, 0, b'11111111']
[2, False, False, 1, b'22222222']
[4, False, False, 3, b'44444444']
[5, False, False, 0, b'55555555']
[6, False, False, 1, b'66666666']
[8, False, False, 3, b'88888888']
cb0a
pending
cb1a
pending
[1, False, False, 0, b'11111111']
[5, False, False, 0, b'55555555']
