LED & Music

Instructions in this category drive the WS2812B full-color LEDs and the sound generator.

The WS2812B module can be enabled with the WS2812B Switch 0xCB (automatic since the 2026-09 firmware), and the MIDI player requires Playtune to be activated with the Playtune Switch 0xD0.

0xE4 Set Color of One LED (CD)

Set the color of a single WS2812B LED by its index. Each color component is an 8-bit value (0~255). If the current mode is OFF, it is switched to ON automatically.

Instruction Form

000  E4  00FF  8000    LED 0 = orange (FF8000)

Mnemonic Form

000  CD  00FF  8000    LED 0 = orange (FF8000)

info

Operands	Value/Range	Remark
OP-00	00~0B	LED index (12 LEDs on board)
OP-01	00~FF	Red component
OP-10	00~FF	Green component
OP-11	00~FF	Blue component

0xE5 Set LED Colors from Registers (RCD)

Fill one or more consecutive LEDs with a single color taken from three consecutive registers R[n]~R[n+2] (R, G, B). OP-01 selects which byte of each register is used: 00 = low 8 bits, any other value = high 8 bits. If the current mode is OFF, it is switched to ON automatically.

Instruction Form

000  10  0010  1234    R10 = 1234
001  10  0011  5678    R11 = 5678
002  10  0012  9ABC    R12 = 9ABC
003  E5  1001  0006    LED 0~5 = color 12569A (high bytes)

Mnemonic Form

000  FZ  0010  1234    R10 = 1234
001  FZ  0011  5678    R11 = 5678
002  FZ  0012  9ABC    R12 = 9ABC
003  RCD 1001  0006    LED 0~5 = color 12569A (high bytes)

With OP-01 = 01, the high bytes of R10~R12 (12, 56, 9A) form the color 12569A; with OP-01 = 00, the low bytes would form 3478BC.

info

Operands	Value/Range	Remark
OP-00	00~FF	Starting register number n (R[n]~R[n+2] = R, G, B)
OP-01	00	Use the low 8 bits of each register
	other	Use the high 8 bits of each register
OP-10	00~0B	Starting LED index
OP-11	01~0C	Number of LEDs to fill

0xE6 Set LED Mode

Set the working mode of the WS2812B LEDs.

000  E6  0002  0000    breath mode

info

Operands	Value/Range	Remark
OP-00	00	Ignored
OP-01	00	OFF
	01	ON — show the colors set by 0xE4/0xE5
	02	Breath
	03	Full white
OP-1	0000	Ignored

0xE7 Set Breath Parameters

Configure the breath light effect. The mode must be set to breath (0xE6 with OP-01 = 02) beforehand.

000  E6  0002  0000    switch to breath mode first
001  E7  05C0  000B    5 steps, interval C0, LEDs 0~11

info

Operands	Value/Range	Remark
OP-00	00~FF	Breath step count
OP-01	00~FF	Breath interval
OP-10	00~0B	Starting LED index
OP-11	00~0B	Ending LED index

0xE8 Play a Tone (FY)

Play one note on the buzzer. OP-0 describes the pitch, OP-1 the duration.

The note byte (OP-01) combines the octave in its high 4 bits (02) and the note name in its low 4 bits (17 = C D E F G A B). Values out of range play a rest. Octave code 0/1/2 corresponds to octave 3/4/5 — for example 11 = C4, 15 = G4 and 05 = G3.

info

Operands	Value/Range	Remark
OP-00	00	Natural note
	01	Sharp
	02	Flat
OP-01	high 4 bits 0~2	Octave 3/4/5
	low 4 bits 1~7	Note name 1=C 2=D 3=E 4=F 5=G 6=A 7=B
	other	Out of range: rest
OP-1	0000~0009	Duration slot number, see table below (16-bit whole)

Duration slots (only slots 0~9 are valid):

Slot	Duration	Slot	Duration
0	31 ms	5	250 ms
1	62 ms	6	375 ms
2	94 ms	7	500 ms
3	125 ms	8	1000 ms
4	187 ms	9	2000 ms

A slot of 10 or above is silent.

tip

For classroom melodies, slots 3 / 5 / 7 (125 / 250 / 500 ms) cover most rhythm patterns — roughly sixteenth, eighth and quarter notes at a moderate tempo.

caution

The slot number must be written into the low byte of OP-1 (P11); the high byte P10 always stays 00. Putting the slot into the high byte — e.g. E8 0015 0500 — makes the 16-bit value 1280, which is ≥ 10, and the note is silent.

Instruction Form

000  E8  0015  0007    G4, slot 7 (500 ms)
001  E8  0011  0005    C4, slot 5 (250 ms)
002  E8  0105  0003    G#3, slot 3 (125 ms)
003  E8  0000  0003    note out of range = rest

Mnemonic Form

000  FY  0015  0007    G4, slot 7 (500 ms)
001  FY  0011  0005    C4, slot 5 (250 ms)
002  FY  0105  0003    G#3, slot 3 (125 ms)
003  FY  0000  0003    note out of range = rest

note

While a note plays, the melody generator temporarily occupies the buzzer; when playback finishes, the on-board PWM (PB3) is available again.

0xFE Play MIDI

Play a score through the Playtune engine. Playtune must be activated with the Playtune Switch 0xD0 beforehand.

000  D0  0000  0001    activate Playtune first
001  FE  0000  0008    play the score starting at line 008
002  0F  0000  0000    program end

Lines from 008 onwards store the score data. They are not executed as instructions: playback is blocking — the program waits until the tune finishes — and the program counter skips the score lines automatically.

info

Operands	Value/Range	Remark
OP-00	00	Ignored
OP-01	00~FF	Line number of the first score line
OP-1	0000	Ignored