Raspberry Pi 3 B+ They have built in Bluetooth and a 4 core processor. Each core is a ARM Cortex-A53.
We are using dotstar LED strips which take a clock (yellow) and a data (green) line. The input is a Buffer of bytes.
Max clock rate 30 MHz
They accept an SPI protocol, but the LED strips are not SPI slave devices themselves. That is, they don't accept a channel select (CS) input. We have to use a demultiplexer chip to route the connections. CD4052BE
There are 2 SPIs on a Raspberry pi 3, with 2 and 3 Channel Selects (CS) respectively.
- /dev/spidev0.0
- /dev/spidev0.1
- /dev/spidev1.0
- /dev/spidev1.1
- /dev/spidev1.2
We will use SPI 0 for the LEDs and SPI 1 to connect to the sensors.
On the demultiplexer chip there are two inputs, A & B, that take LOW or HIGH values to select which channel to connect to.
| CH | B | A |
|---|---|---|
| 0 | 0 | 0 |
| 1 | 0 | 1 |
| 2 | 1 | 0 |
| 3 | 1 | 1 |
This will not work with the CH pins and instead we have to use GPIO pins and manually select the channel before sending a Buffer.
We are also using an MCP3004 analog-to-digital chip. It takes 4 analog inputs and stores them in a buffer. The digital side uses an SPI protocol.
- 200 ksps max. sampling rate at VDD = 5V
- 3.6 MHz clock speed for 5V
- 10 kHz is the minimum clock speed to not lose data
- CS line has to be LOW to read data.
All fixtures will have:
- Ch 0 a microphone CMA-6542PF
The audio sampling rate of 48 ksps is a standard.
and fixtures 1 and 6 will have:
-
Ch 1 a distance sensor GP2Y0A710K0F
-
CH 2 and an ambient light sensor TSL257-LF
This leaves 1 or 3 channels open for future analog devices.
There are also 2 motion sensors per light fixture - https://learn.adafruit.com/pir-passive-infrared-proximity-motion-sensor/ These have logic output which is HIGH for motion.