Mixing and Matching Custard Pi’s

 

Introduction

 

If a particular Custard Pi does not have all the right inputs and outputs, then it’s possible to combine more than one. This post looks at the various combinations that are possible.

 

For more examples click here to go to the blog post

 

GPIO bus connection method

 

The various cards use different means of connecting to the Raspberry Pi GPIO and this summarised below.

 

SPI bus

I2C bus

8 digital I/O

Custard Pi 2

Custard Pi 6

Custard Pi 1

Custard Pi 3

Custard Pi 7

Custard Pi 2

 

 

Custard Pi 5

 

The card combinations are limited by the type of bus connection used. For example, the SPI bus can only address 2 devices. As the Custard Pi 2 has a Analogue to Digital Convertor (ADC) and a Digital to Analogue Convertor (DAC) and both of these use the SPI bus, you cannot have more than 1 Custard Pi 2 connected to the GPIO. Because the Custard Pi 3 also uses the SPI bus, you cannot have a Custard Pi 2 and a Custard Pi 3 connected to the Raspberry Pi at the same time.

 

The I2C bus is addressable and you can have as many I2C devices as there are addresses. This means that you can have up to 8 Custard Pi 6’s connected at the same time. You just have to make sure that the switches on each card are used to set a different I2C address.

 

Example 1 - 64 relays controlled from the Raspberry Pi

 

Eight Custard Pi 6 cards daisy chained to provide a total of 64 relays that can be controlled from the Raspberry Pi GPIO.

 

P1040007.JPG

 

 

Example 2 - 8 relays and 8 analogue inputs

 

This is achieved by using a Custard Pi 6 and a Custard Pi 3. As one uses the I2C bus and the other uses the SPI bus, this is possible.

 

For more examples click here to go to the blog post