Peripheral Configuration

Instructions in this category switch peripheral modules on or off, and configure the on-board PWM, the external PCA9685 PWM modules, the real-time clock and the Playtune audio engine.

0xC0 Module Configuration (MKPZ)

Enable or disable several modules at once. OP-1 is a 16-bit switch map that replaces the whole peripheral switch bitmap (same bit assignment as register R34). Every bit of the map takes effect: a module whose bit is 0 is switched off.

bit	Module
0	ADS1115 AD converter (0xC1)
1	BME280 environment sensor (0xC3)
2	DS1307 real-time clock (0xCA)
3	TCS34725 color sensor (0xC4)
4	PCA9685 PWM generator (0xC5)
6	WS2812B full-color LEDs (0xCB)
8	OLED display
11	Melody generator (0xE8)

000  C0  0000  0105    ADS1115 + DS1307 + OLED on, all others off

0105 corresponds to the binary value 0000 0001 0000 0101: bit 0, bit 2 and bit 8 are set, exactly the three modules named in the comment above.

info

Operands	Value/Range	Remark
OP-0	0000	Ignored
OP-1	0000~FFFF	Switch map, one bit per module (table above)

Module Switches: Common Format

The six single-module switch instructions 0xC1, 0xC3, 0xC4, 0xC5, 0xCA and 0xCB share the same five-byte layout XX 00 ss 00 00, where ss = 01 enables and any other value disables the module.

info

Operands	Value/Range	Remark
OP-00	00	Ignored
OP-01	01	Enable the module
	other	Disable the module (00 recommended)
OP-1	0000	Ignored

Instruction Form

000  C1  0001  0000    enable the ADS1115 module
001  C1  0000  0000    disable the ADS1115 module

Mnemonic Form

000  C1  0001  0000    enable the ADS1115 module
001  C1  0000  0000    disable the ADS1115 module

tip

Since the 2026-09 firmware, the power-on self-test automatically enables every module it detects, so example programs generally no longer need explicit enable instructions. These switches are still useful for deliberately disabling a module, or for re-enabling one after it has been switched off.

0xC1 ADS1115 Switch

Enable or disable the ADS1115 analog-to-digital converter module.

tip

Once enabled, the conversion results are maintained in R40~R4F — see Sensors.

0xC3 BME280 Switch

Enable or disable the BME280 environment sensor (temperature, humidity and pressure).

tip

The sensor readings are maintained in R2E~R30.

0xC4 TCS34725 Switch

Enable or disable the TCS34725 color detection sensor.

0xC5 PCA9685 Switch

Enable or disable the PCA9685 external PWM generator module.

tip

The external PWM instructions 0xE1~0xEF below require this module to be enabled.

0xCA DS1307 Switch

Enable or disable the DS1307 real-time clock module. Once enabled, the time data is kept up to date; a new time can be written with 0xE3.

0xCB WS2812B Switch (MKCD)

Enable or disable the WS2812B full-color LED module. The LED instructions are described in LED & Music.

0xCC On-board PWM Duty Cycle (PWM)

Set the duty cycle of the on-board PWM channels: CH1=PB4, CH2=PB3, CH3=PB0, CH4=PB1.

000  CC  0001  01F4    single channel: CH1 duty = 500
001  CC  FF05  01F4    bit mask: CH1 and CH3 duty = 500

In the second line, 05 selects the channels by bit (b0101 = CH1 and CH3).

info

Operands	Value/Range	Remark
OP-00	FF	Bit-mask mode: OP-01 selects the channels by bit
	other	Single-channel mode (00 recommended)
OP-01	00~03	Channel number (single-channel mode)
	00~0F	Channel bit mask, bit0=CH1 … bit3=CH4 (bit-mask mode)
OP-1	0000~03E7	Duty cycle; written only when the value is below 1000

Advanced

While a melody (0xE8) or a MIDI playback (0xFE) occupies the audio pin, the affected PWM channel is not reconfigured.

0xD0 Playtune Switch

Activate or restore the Playtune audio engine. Value 01 switches the audio system to the three-channel MIDI mode required by the MIDI player 0xFE; value 00 restores the on-board PWM.

000  D0  0000  0001    activate Playtune (MIDI mode)

info

Operands	Value/Range	Remark
OP-00	00	Ignored
OP-01	01	Activate Playtune (MIDI three-channel mode)
	00	Restore on-board PWM
OP-1	0000	Ignored

16-bit Whole Operands

From 0xE1 onwards, most operands in this chapter are interpreted as 16-bit wholes: OP-0 and OP-1 are each taken as a single 16-bit value (one four-digit hex number) rather than two independent 8-bit halves. For example, in E1 0003 01FF the value 0003 is the channel mask and 01FF is the duty cycle — neither is split into bytes. See also the operand notation in Brief.

0xE1 External PWM: Channels by Mask, Immediate Duty

Set the duty cycle of the 16 channels of PCA9685 module 0 in one instruction. Every channel whose mask bit is 1 receives the duty value.

000  E1  0003  01FF    channels 0 and 1, duty = 01FF (about 12.5%)

info

Operands	Value/Range	Remark
OP-0	0000~FFFF	16-channel bit mask (bit0 = channel 0 … bit15 = channel 15)
OP-1	0000~0FFF	Duty cycle, 12-bit resolution

tip

0xE1 addresses module 0 only. To update several PCA9685 modules at once, use 0xEB or 0xEC.

0xE2 External PWM: Channels by Mask, Duty from Register

Same channel selection as 0xE1, but the duty cycle is taken from a register.

Instruction Form

000  10  0020  01FF    R20 = 01FF (duty)
001  E2  0003  0020    channels 0 and 1, duty from R20

Mnemonic Form

000  FZ  0020  01FF    R20 = 01FF (duty)
001  E2  0003  0020    channels 0 and 1, duty from R20

info

Operands	Value/Range	Remark
OP-0	0000~FFFF	16-channel bit mask
OP-1	00~FF	Register number; duty cycle = R[reg]

0xE3 Write RTC Time

Write a new time to the DS1307 real-time clock. Seven consecutive registers starting at OP-01 hold year, month, day, weekday, hour, minute and second. The write runs in the background.

Instruction Form

000  10  0030  001A    R30 = 26  (year)
001  10  0031  0009    R31 = 9   (month)
002  10  0032  0019    R32 = 25  (day)
003  10  0033  0005    R33 = 5   (weekday)
004  10  0034  000A    R34 = 10  (hour)
005  10  0035  001E    R35 = 30  (minute)
006  10  0036  0000    R36 = 0   (second)
007  E3  0030  0000    write R30~R36 to the RTC

Mnemonic Form

000  FZ  0030  001A    R30 = 26  (year)
001  FZ  0031  0009    R31 = 9   (month)
002  FZ  0032  0019    R32 = 25  (day)
003  FZ  0033  0005    R33 = 5   (weekday)
004  FZ  0034  000A    R34 = 10  (hour)
005  FZ  0035  001E    R35 = 30  (minute)
006  FZ  0036  0000    R36 = 0   (second)
007  E3  0030  0000    write R30~R36 to the RTC

info

Operands	Value/Range	Remark
OP-00	00	Ignored
OP-01	00~FF	Starting register number; R[n]~R[n+6] = year, month, day, weekday, hour, minute, second
OP-1	0000	Ignored

The Three-Module Mask Mechanism

The external PWM port supports up to three PCA9685 modules — module 0, 1 and 2, 16 channels each (Port46, see Brief). For 0xEB0xEE, OP-0 is the number n of the first of three consecutive mask registers:

Register	Content
R[n]	16-channel bit mask of module 0
R[n+1]	16-channel bit mask of module 1
R[n+2]	16-channel bit mask of module 2

0xEB and 0xEC update the masked channels of all three modules in one instruction (up to 48 channels); 0xED and 0xEE update only module 1 and module 2 respectively, using the corresponding mask register R[n+1] / R[n+2].

0xEB External PWM: Three Modules, Immediate Duty

Apply an immediate duty cycle to the channels of all three modules selected by the mask registers.

Instruction Form

000  10  0040  0003    R40 = module 0 mask (channels 0 and 1)
001  10  0041  0001    R41 = module 1 mask (channel 0)
002  10  0042  0000    R42 = module 2 mask (none)
003  EB  0040  01FF    apply duty 01FF to all masked channels

Mnemonic Form

000  FZ  0040  0003    R40 = module 0 mask (channels 0 and 1)
001  FZ  0041  0001    R41 = module 1 mask (channel 0)
002  FZ  0042  0000    R42 = module 2 mask (none)
003  EB  0040  01FF    apply duty 01FF to all masked channels

info

Operands	Value/Range	Remark
OP-0	0000~00FF	Mask register number n (R[n]~R[n+2] = module 0/1/2 masks)
OP-1	0000~0FFF	Duty cycle, 12-bit resolution

0xEC External PWM from Register (WPWM)

Register version of 0xEB: the duty cycle is taken from a register. One instruction refreshes up to 48 channels across all three modules.

Instruction Form

000  10  0040  0003    R40 = module 0 mask
001  10  0041  0001    R41 = module 1 mask
002  10  0042  0000    R42 = module 2 mask
003  10  0050  01FF    R50 = 01FF (duty)
004  EC  0040  0050    refresh all masked channels, duty from R50

Mnemonic Form

000  FZ  0040  0003    R40 = module 0 mask
001  FZ  0041  0001    R41 = module 1 mask
002  FZ  0042  0000    R42 = module 2 mask
003  FZ  0050  01FF    R50 = 01FF (duty)
004  WPWM  0040  0050    refresh all masked channels, duty from R50

info

Operands	Value/Range	Remark
OP-0	0000~00FF	Mask register number n (R[n]~R[n+2] = module 0/1/2 masks)
OP-1	00~FF	Duty register number; duty cycle = R[reg]

0xED External PWM: Module 1 from Register

Same as 0xEC, but only module 1 is updated (mask register R[n+1]).

000  10  0041  00F0    R41 = module 1 mask (channels 4~7)
001  10  0050  0800    R50 = 0800 (duty)
002  ED  0040  0050    update module 1 only, duty from R50

info

Operands	Value/Range	Remark
OP-0	0000~00FF	Mask register number n; mask read from R[n+1]
OP-1	00~FF	Duty register number; duty cycle = R[reg]

0xEE External PWM: Module 2 from Register

Same as 0xEC, but only module 2 is updated (mask register R[n+2]).

000  10  0042  0001    R42 = module 2 mask (channel 0)
001  10  0050  0400    R50 = 0400 (duty)
002  EE  0040  0050    update module 2 only, duty from R50

info

Operands	Value/Range	Remark
OP-0	0000~00FF	Mask register number n; mask read from R[n+2]
OP-1	00~FF	Duty register number; duty cycle = R[reg]

0xEF Set PWM Frequency (WPL)

Set the PWM frequency of one PCA9685 module (0, 1 or 2), in Hz.

000  EF  0000  03E8    module 0: PWM frequency 1000 Hz

info

Operands	Value/Range	Remark
OP-0	0000~0002	Module number
OP-1	0000~FFFF	Frequency in Hz (the PCA9685 supports roughly 24~1526 Hz)

caution

Setting the frequency suspends the channel refresh: after 0xEF runs, the channels keep their last output until the next WPWM 0xEC is executed.