Thanks @Lenny for the detailed reply. I get the I2C limitation, especially with 3 of the same unit with non-programmable address. Using the controller chipset directly on a custom board rather than via a development board makes that less of a problem as the ESP32 can handle multiple I2C busses. There are also SPI versions of the pressure sensors available so they could go on a single SPI bus. I'm deleting the GPS idea and will implement the pressure sensors as you have them. I'm putting an audio codec on the board for the audio out via I2S. It's not expensive and can handle 16bit stereo and has "pop reduction"; libraries may be interesting - that teensy Audio library is really nice and I may try to port some of it! This may take a while! I'll let you know how I get on. Cheers, Gareth.

Hi Max, Gen 2 requires the Teensy. It does the bulk of the calculations. I'm proposing to build a Gen2 Lite (or perhaps more accurately a stand-alone) version but that does not affect the parts you have right now to build a Gen 2. Vac, Thanks for your answer. I've spent some time going through the code and the board design and mostly figured out what's doing what and when! I think I need a Zoom with Lenny! 😀 My thoughts at this point regarding a Lite / stand-alone version: 1. The thing I like best about this project is the audio nature of it. Eyes stay outside and I imagine reaction to the tones becomes Pavlovian. The stereo ball feature is intriguing, I'm not proposing to support the display. Question: does this version NEED a display? 2. The external data from EFIS and GPS seem to be used only during calibration, the OAT does not appear to be used at all. I propose not to include these three connections making the code and the physical installation simpler. 3. I'm (amateur) designing a custom board with the ESP32 WiFi-capable microcontroller and a LSM6DSO32X IMU (AHRS) chip mounted directly on the board. JLCPCB can work such magic so only the pressure sensors and connectors would need hand soldering! The whole thing could be as small as 100x60mm, a dimension carefully chosen based on me having a suitable enclosure left over from another project! 😛 Jokes apart it reduces the price too and the space is no longer needed with fewer components and no sub-boards! 4. I'm contemplating either having a GPS chip on the board (<$5) with an external antenna connector OR providing connection for an external USB GPS module ($7ish). This could be connected for calibration (placed on the glare shield) and then disconnected and put away. The USB (A type) connector is not suitable for operational use, but would be OK for calibration runs. If the GPS is to be permanently connected I would opt for the chip and connector. 5. I think the AoA calculation could be done with 3 absolute pressure sensors (Pitot, Static, AOA-offset) rather than 2 differentials and an absolute. This would remove the need for the 3-way split of the static line simplifying the tubing arrangement and cut down to sourcing three units of the same pressure sensor model at about $25 each. I need to understand the level of precision required here and whether the measurements of the differential sensors are better than the absolute ones. However ... The biggest question I have is can a single differential pressure sensor between Pitot and AoA, i.e. no static reference provide sufficient AoA data? If we don't need IAS then we don't need static pressure and if we're only after the difference between Pitot and AoA then can we just measure it. @Lenny: p_45/p_fwd is the key value for finding where we are on the curve. p_45 is differential vs static and p_pwd is also differential vs static, if we divide them then we remove the static and are simply comparing the two against each other. Could we not do that with a single differential pressure transducer? Note: This assumes we don't need IAS for operation and the speed in calibration can be got from the GPS: this may be inadequate. Thoughts? Cheers, Gareth. External USB like this might work for calibration runs.