Logic Analyser

Raspberry Pi bare metal programming.

Its one of those devices that comes is very handy, particularly when you're diagnosing a fault in some gated control circuit, or looking at communications signals (serial, spi, i2c etc)

I normally use a PC connected logic analyser, but it always seems like such a effort to boot the old PC up, wait until its ready then capture some data just to get some timings or even just to see the shape of the signals.

So having made a few programs on the raspberry that operate sans OS, I thought this may be a good application

At the moment there is no buffer circuit (the only device attached is an RF 433 receiver). But I will soon be making a board to house a suitable bus transceiver chip, the serial port, rotary encoder switch/s and buttons that are required to interact with the device.

The image below is a quick photo (no save to jpg option on this device at the moment) so the angles may look a little off. But it captures data (1Mhz capture rate, 1024K samples recorded) and that seems to be more than I need at the moment.

The controls are :

  • A rotary encoder switch to manoeuvre the cursor left-right
  • A button to initiate a capture
  • A button to zoom out
  • Two buttons to select Start and End positions using cursor

The serial port can be used to drive the user interface, and is likely to be the source of a configuration script (to name the inputs, adjust the display and potentially export the capture in OLS format)

Posted on Jan 1
Written by Andrew Ord