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Project Notes

#190 MultiSlaveSPI

Using SPI to control multiple devices (that support an SPIish interface)

Here’s a quick video of the circuit in action:



The ShiftDriveSPI project demonstrated how hardware SPI can be used to control a system with a 74HC595 interface. The proposed benefit was that SPI allows multiple devices to be controlled with a minimal (+1) extension to the number of pins required.

This project is a test of SPI to control multiple (2) devices that support an “SPI-like” interface.

It’s interesting how far you can push the definition of “SPI-like”. In this case I’m using two devices:

These modules are all connected to the SPI interface of an Arduino, with a seperate latch (SS/slave select) for each. The data to each module actually passes down the same wire (MOSI).

The demo sketch does two things:

  • runs a 0-9 counter on the 7-segment LED module (with decimal point enabled for even numbers)
  • runs a countdown counter that cycles for each change on the LED module



The Schematic

The Build

Credits and References

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This page is a web-friendly rendering of my project notes shared in the LEAP GitHub repository.

LEAP is just my personal collection of projects. Two main themes have emerged in recent years, sometimes combined:

  • electronics - usually involving an Arduino or other microprocessor in one way or another. Some are full-blown projects, while many are trivial breadboard experiments, intended to learn and explore something interesting
  • scale modelling - I caught the bug after deciding to build a Harrier during covid to demonstrate an electronic jet engine simulation. Let the fun begin..
To be honest, I haven't quite figured out if these two interests belong in the same GitHub repo or not. But for now - they are all here!

Projects are often inspired by things found wild on the net, or ideas from the many great electronics and scale modelling podcasts and YouTube channels. Feel free to borrow liberally, and if you spot any issues do let me know (or send a PR!). See the individual projects for credits where due.