[posted] My first Teensy 4.0 project and radio link to Feather MO + printer


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I have had fun developing a Chronograph for measuring bullet speed with a Teensy 4.0 with 3.2in tft and RFM69 radio link to a Feather M0 with the 433mhz onboard radio.
Also added a Nano printer to the wireless display for a hardcopy at the shooting range. The Feather M0 was easier to setup sharing the SPI between the radio and the 1.9in tft display
than the Teensy 4.0. The other obstacle was learning to send big endian to small endian, but the Radiohead library was very helpful. Chrono uses piezo sensors taped to the corner of PET film
for sensing the bullet strike capturing the time elapsed over 1ft spacing. attached 2 photos of finished devices



  • chrono.jpg
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  • wireless display and printer.jpg
    wireless display and printer.jpg
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  • chrono with PET film.jpg
    chrono with PET film.jpg
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Neat project! I don't think I've seen PET film used as a sensor before. I started looking at trying to use a Magnetospeed sensor, but had difficulties seeing the signal on my o'scope while also getting a reading. I've always wanted to include air/barrel temperature as well as time of day/delta seconds between shots to better understand the impact of temperature has on velocity.