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#Technical Reference

Temperature/Pressure via BMP280, i2c: 0x77

Temperature and Pressure readings are supplied by the BMP280.

See the BMP280 datasheet for details.

4-digit Alphanumeric Character Display via HT16K33, i2c: 0x70

The HT16K33 controller is connected to four, 14-segment star displays with decimal points.

See the HT16K33 datasheet for details.

Piezo Transducer

The piezo transducer is connected to BCM#13 / PWM1.

7 Element APA102 Rainbow via SPI0 with chip-select CE0

The rainbow arc consists of 7 APA102 RGB pixels numbered 0 to 6 from right to left.

Function GPIO Pin
Clock BCM#11
Data BCM#10
Chip-Sel BCM#8

It's a write-only device requiring a 37 byte update transaction.

  • Start frame of 32 zero bits
  • Data for seven 32 bit pixels:
  • 8-bit start frame of 0b11100000 + 5bit brightness value
  • 8-bit blue value
  • 8-bit green value
  • 8-bit red value
  • End frame of at least 36 zero bits

3 Touch Inputs via AT42QT1070

The 3 touch inputs, labelled A, B and C, are driven by an AT42QT1070 QTouch controller.

The pins are active low, and should be set up as inputs with the pull-up resistors enabled.

Input GPIO Pin
A BCM#21
B BCM#20
C BCM#16

Only one touch can be registered at a time, and a touch will time out after being continually held for more than about 30 seconds.

3 LEDs, Red, Green and Blue via GPIO

The 3 LEDs are connected to the following GPIO pins.

Each is connected via a 1k current limiting resistor.

LED GPIO Pin
Red BCM#6
Green BCM#19
Blue BCM#26