picadae/control/tiny/README.md

ATtiny85 I2C protocol

Arguments in curly braces are optional.

---

Hold PWM Duty Cycle

Function	Opcode	Arguments
Set hold PWM duty cycle	0	(duty) { (freq) { (div) }}

Arguments	Range	Default	Note
(duty)	0-255	127	0=0%, 255=100%
(freq)	0-255	255	Sets PWM top value
(div)	1-15	5	Set the PWM base clock frequency (See table below)

PWM frequency and period for each possible (div) setting.

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

---

Note-on Velocity

Function	Opcode	Arguments
Note on velocity	1	(vel)

Arguments	Range	Default	Note
(vel)	0-127	n/a	Note on velocity.

Execute a note onset. The (vel) value is translated to an attack pulse duration by looking up the pulse tick count in the velocity table.

---

Note-on Microseconds

Function	Opcode	Arguments
Note on ticks	2	(pulse-ticks-high-byte) (pulse-ticks-low-byte)

Execute a note onset. The 16 bit attack duration in ticks is calculated from microseconds.

pulse-ticks = (usec / 1e6) * (16e6/256)

Where 16e6 is the system clock frequency and 256 is the timer0 clock divider. TCCR0B:C02,C01,C00 = 100b (4)

ticks to micoseconds:

usecs = (pulse-ticks * 1e6)*(256/16e6)

---

Note-off

Function	Opcode	Arguments
Note off	3	None

Turn off a sounding note by settting the hold-voltage to 0.

---

Set Read Address

Function	Opcode	Arguments
Set read address	4	(src) {(addr)}

Set the source and address of the next I2C read request.

The read can come from one of three memory banks: Register File, MIDI velocity table or EEPROM. See the Memory Source Id Table below for the (src) id values.

Arguments	Range	Default	Note
(src)	0-2	n/a	Memory location id. See Memory Source Id Table.
(addr)	0-255	n/a	Offset from base address set by (src)

Memory Source Id Table

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

---

Write Memory

Function	Opcode	Arguments
Write memory	5	(addrFl + dest) {(addr)} (value0) … (valueN)

Arguments	Range	Default	Note
(addrFl)	0,127	0	Address flag. Set if second byte is an (addr) and not (value0)
(dest)	0-2	n/a	Memory destination location. See Memory Destination Id Table.
(addr)	0-255	n/a	Optional offset from base address set by (dest)

Memory Destination Id Table

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

---

Write Velocity Table to EEPROM

Function	Opcode	Arguments
Write velocity table	6

Writes the MIDI velocity table from memory to EEPROM.

---

Set Hold Delay

Function	Opcode	Arguments
Set hold delay	7	{ high {low}}

Set the length of the delay, in ticks, between when the attack pulse ends and when the hold voltage is applied. The high and low byte values are calculated identically to the attack pulse duration values.

---

Set flags variable

Function	Opcode	Arguments
Set flags variable	8	(flags)

7	6	5	4	3	2	1	0
n/a	n/a	n/a	n/a	n/a	n/a	n/a	HOA

HOA : Set to apply the hold voltage at the beginning of the attack.

---

Register File Address

Address	Label	Note
0	Reg_Rd_Addr	Next register file address to read.
1	Table_Rd_Addr	Next MIDI velocity address to read.
2	EEPROM_Rd_Addr	Next EEPROM address to read.
3	Read_Src_Addr	Source of the next I2C read request. See Memory Location Id table below.
4	Reg_Wr_Addr	Next register file address to write.
5	Table_Rd_Addr	Next MIDI velocity address to write.
6	EEPROM_Rd_Addr	Next EEPROM address to write.
7	Write_Dst_Addr	Destination of the next ‘write operation’. See Memory Location id table below.
8	Tmr_High_Addr	Current attack pulse tick count high byte
9	Tmr_Low_Addr	Current attack pulse tick count low byte
10	Tmr_Div_Addr	Attack pulse counter frequency divider.
11	Pwm_Duty_Addr	Duty cycle of the hold PWM generator
12	Pwm_Freq_Addr	PWM counter max values. Determines the PWM frequency.
13	Pwm_Div_Addr	PWM clock divider
14	State_Addr	Current solenoied state.
15	Error_Addr	Error status
16	Max_Tmr_Hi_Addr	Max attack pulse high byte tick count.
17	Delay_High_Addr	Hold delay onset tick count high byte
18	Delay_Low_Addr	Hold delay onset tick count low byte
19	Flags_Addr	Binary variable field.

---