[Happy Little Diodes] built a Pi Pico logic analyzer designed by [El Dr. Gusman] using the original design. But he recently had a chance to test the newest version of the design, which is a big upgrade. You can see his take on the new design in the video below.
The original design could sample 24 channels at 100 MHz and required two different PCBs. The new version uses a single board and can operate up to 400 MHz. There’s also a provision for chaining multiple boards together to get more channels.
You can set the level shifters to use 5V, 3.3V, or an external voltage. Since [Happy] is working on a ZX Spectrum, the 5V conversion is a necessity.
One thing that a cheap logic analyzer lets you do is dedicate it to a particular purpose. In fact, by the end of the video, we see a dedicated connector to make it easier to attach the board to a ZX Spectrum.
The code is on GitHub, although it warns you there that you that version 6 — the one seen in the video — isn’t stable, so you might have to wait to make one on your own. The software looks impressive and there may be some effort to integrate with Sigrok.
If you missed our coverage of the earlier version, you can still catch up. Dead set on Sigrok support? [Pico-Coder] can help you out.
I am travelling so I cannot watch the video, but how does is the sampling rate reach 400MS/s? Is the creators overclocking the 133MHz ARM cores? I know RP2040 is dual core, so I wonder if they can/are “staggering” the running of the code on the two cores to get better sampling rate?
Very cool project, always loved the concept of using cheap dev boards as logic analyser. Back when i was in univ I wrote my own logic analyzer for an AVR to record the IR signals to an air conditioner. Fun times.
I’m more curious how he’s getting the data off the rp2040. When I messed with using one as a logic analyzer the number one limit was the USB 1.0 being too slow to offload the data in real time. So you’d rapidly fill the RAM and could only sample for short periods.