Picadea control and monitor shell

Shell commands:

key	Function	Arguments	Notes
q	quit
?	print usage
w	write	(i2c_addr) (reg_addr) (data0) ... (dataN)
r	read	(i2c_addr) (src) (reg_addr) (byteN)	See Memory Source Id Table.
v	note-on	(pitch) (vel)
u	note-on	(pitch) (usec) (div)	See Pulse Timer Divisor Table.
o	note-off	(pitch)
T	set table	(pitch) (vel) (usec)
t	get table	(pitch) (vel)
D	set duty	(pitch) (percent) {(hz) {(div)}}
d	get duty	(pitch)
H	set hold delay	(pitch) (usec)
h	get hold delay	(pitch)
F	set pwm freq	(pitch) (hz)	254=~123Hz
f	get pwm freq	(pitch)
I	set pwm div	(pitch) (div)	See PWM Divisor Table.
i	get pwm div	(pitch)
A	set flags	(pitch) (flags)
a	get flags	(pitch)
W	write table	(pitch)
N	note w/ duration	(pitch) (atkUs) (durMs)
S	seq	(pitch) (atkUs) (durMs) (deltaUs) (noteN)
L	log	(level) (0-1)

PWM Divisor

Value	Div	Frequency	Period
1	1	16 M	62.5 n
2	2	8 M	125 n
3	4	4 M	250 n
4	8	2 M	500 n
5	16	1 M	1 u
6	32	500 K	2 u
7	64	250 K	4 u
8	128	125 K	8 u
9	256	62500 Hz	16 u
10	512	31250 Hz	32 u
11	1024	15625 Hz	64 u
12	2048	7812.5 Hz	128 u
13	4096	3906.25 Hz	256 u
14	8192	1953.125 Hz	512 u
15	16384	976.6625 Hz	1024 u

Value	Divisor	Frequency	Period
1	1	16000000	62.5n
2	8	2000000	500.0n
3	64	250000	4.0u
4	256	62500	16.0u
5	1024	15625	64.0u

Id	Memory	Note
0	Register file	See register table file
1	Velocity table	MIDI velocity to pulse ticks lookup table
2	EEPROM	EEPROM data memory

Id	Memory	Note
4	Register file	See register table file
5	Velocity table	MIDI velocity to pulse ticks lookup table
6	EEPROM	EEPROM data memory