2025-05-11: A somewhat working Dev Rig

The dev rig lives! Or at least it’s kinda-sorta closed up, and it kinda-sorta works.

Let’s start with a quick clip.

To give a short explanation as to what you’re looking at, this is my current Dev Rig. It used to be a Rancilio Silvia, but there’s not that many of the original components left in it. It now features the following:

• Fluid-o-tech FG304 gear pump
• Digmesa Nano-brass flow meter
• Xidibei XDB401 pressure transducer
• PT100 temperature probe, drilled in to the original boiler
• SSD1309 OLED display
• Fairly shitty rotary encoder

The OPV, boiler, group, steam wand and solenoid valve are stock.

All of this is controlled via the APEC SoM EV, using the Dev Rig Carrier. The Carrier is mostly passives, the interesting things happen in the APEC SoM.

What’s next?

There’s still a lot of work to do on the firmware. I’m getting to a place where I’m pretty happy with the general architecture, and while things like PID control over the boiler and and pump (neither shown in the video) work but requires parameter tuning, it’s nowhere near done.

Hardware-wise, there’s still things to do as well. I am planning on replacing the board on the right in the picture. The placing of the 24V connector is unfortunate, because it means I can’t have the case closed with both a USB cable and the 24V connector plugged in at the same time. As the keen-eyed have noted, the board on the left has some quirks as well, but while I have updated the PCB files, I’m not planning on manufacturing the updated version. I only have 5 of the APEC SoM EV1, and removing one soldered to a carrier is both a pain and risky, so I’m not planning on doing that.

I will probably also need to drill some more holes into the frame of the machine to fasten everything, but that shouldn’t be too much of a problem.

Publishing-wise, the schematics and PCB for the Dev Rig carrier will be published when the APEC SoM files are published (sometime around EV2).