Source code and PCB design files for an impedance and temperature measurement instrument.
The instrument features a BNC socket for connecting the device under test (DUT). A standard miniature IEC socket allows the connection of a thermocouple.
The board has been designed in KiCad. You can use it to generate your own Gerbers.
Here's a partial BOM:
- Impedance IC: AD5933
- Thermocouple IC: MCP9600
- Mux: ADG729
The control terminal is a Seeed Studio reTerminal which is basically a Raspberry Pi CM4 with a touchscreen and some other peripherals.
The software is built as a stage for pi-gen. Just drop it in and include it. There's also a stage for the device tree and display driver of the reTerminal device. Both of these are unfortunately not upstreamed.
After building, the result will be an image that can be directly written to the device. It will boot straight into the UI. The Qt application runs on a DRM framebuffer without a display server (EGLFS). The image has been tested with the 64 bit version of Bullseye.
The code does contain some out-of-tree modifications to the AD5933 IIO kernel driver. It has been extended with variable clock rate support (for low excitation frequencies). In the default implementation the clock is sourced from the Raspberry Pi GPCLK peripheral.
Additionally, there's a tiny patch to libiio (included as a binary package in this repo): https://lore.kernel.org/all/1204b19a92343a9e3a6ec5df3cef94f6777e08c4.camel@jku.at/
There's a manual that can be built with pandoc. Set up a LaTeX environment and run the following to build a PDF:
make pdfYou can also generate a nice printable booklet using:
make bookletThis requires the pdfbook2 script which is part of TeX Live and shipped in the
"texlive-extra-utils" package on Debian.