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RGB LED driven by an ATTiny85. Largely blink(1)-compatible, except that it uses I2C instead of USB.


See and for soldering instructions.

For the firmware, run make && make program. You may need to edit the Makefile to fit your programmer, it's written for an usbasp.

remote control (I2C)

This is enabled by the -DI2CEN compile flag, which is set by default in the Makefile. Hardware pull-ups on SCL and SDA are required (1.5 kOhm recommended)

After sending the 7bit address and the r/!w bit, the bus master must send the following 7 bytes to the MicroMoody:

  • command
  • delay
  • red value
  • green value
  • blue value
  • payload address (high byte)
  • payload address (low byte)

The default I2C address is 0x11 (17), The default payload address is 0x0001. The idea behind this distinction is to use the I2C address to talk to any micromoody, and the payload address to select the specific micromoody to address. This way, you can have various other I2C devices and up to 65534 MicroMoodies on the same bus (just in case you need to).

Commands with the broadcast payload address of 0xffff are always accepted, even when they contain the "set address" opmode.

red, green and blue are the color value, 0 is off, 0xff is full brightness.

There are several types of commands:

command 0 .. 63 (set mode of operation)

The red, green and blue bytes are "don't care" unless a command is marked RGB.

  • 0: steady RGB light
  • 1: rainbow colors, hard transitions
  • 2: random colors, hard transitions
  • 3: RGB color, blink on/off
  • 4: steady light, fade to specified RGB color
  • 5: rainbow colors, fading transitions
  • 6: random colors, fading transitions
  • 7: RGB color, fade on/off
  • 63: Run animation. It will start in slot 1 and end in the slot last set (see also below)

modes 8 to 62 are reserved for further blink / fade modes.

command 64 .. 127 (animation sequences)

  • 64: Save RGB + delay in animation slot 1
  • ...
  • 127: Save RGB + delay in animation slot 64

For instance, to set a steady red pulse, you can transmit (in hex) 40 10 ff 00 00 ff ff, 41 10 50 00 00 ff ff. This will make the animation run in slot 1 -> slot 2 -> slot 1 -> ....

Note that this does not start the animation yet, use 3f XX XX XX XX ff ff for that. Also note that the upper bound of the current sequence is determined by the last animation command. So if you send 40 ..., 41 ..., 42 ..., 40 ..., the animation run will be slot 1 -> slot 1 -> slot 1 -> .... (i.e. a steady color).

Refer to example/*/rgbpulse for a more sophisticated example.

command 128 .. 239


command 240 .. 255 (EEPROM)

These commands access the EEPROM. Writing one byte takes about 3.4ms and is implemented synchronously, so expect them to be slow. They may even cause I2C bus timeouts (which do not indicate write failures).

  • 240: Save current mode of operation (last command < 64) to EEPROM to be recalled after a power cycle. NOTE: if the current opmode is 63 (animation), this may take up to 1 second (~12ms for each used animation slot)
  • 241: Set address to color bytes. payload high = red, payload low = green, i2c = blue. This will also set the operation mode to random fading. Note that for i2c, the least significant 7 bit are the address, while the most significant bit is ignored

commands 242 to 255 are reserved for further EEPROM commands.

I2C master hardware

If you have an Arduino, see examples/arduino/SerialToI2C for a USB-Serial to I2C interface.

Otherwise, see vusb-i2c for a general-purpose USB-I2C tool based on VUSB.

recognizing the firmware state

At the time of this writing, a newly flashed MicroMoody with default address will run the RGB blink mode (starting with yellow), while a newly flashed MicroMoody with only the addresses changed and no mode set will run in rgb fading mode (starting with green).

I2C master operation

When compiled with -DI2CMASTER (disabled by default), the MicroMoody will act as I2C bus master. After each transition (after half the time until the next transition has passed) it will send its current color and fade delay as a broadcast (payload address 0xffff) over the bus. The I2C address used will be the MicroMoody's I2C address (see above for default).

If it is operating with hard transitions, so will the slaves. same for soft (fading) transitions.





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