![]() ![]() ![]() The program would have to calculate the coefficients on the fly and then download them to the filter. Not only that, I would like to have a PC application, somewhat like TFilter, that would allow a user to build his own filter on the fly. I always thought that I’d build mine into a speaker. The Teensy 3.6 costs $30, while the Teensy 3.2 costs only $20. The Teensy 3.2 uses a 72 MHz ARM processor, and apparently, that’s quite enough power for audio DSP. In Gareth’s application, the Teensy is embedded into the FT-817, and somehow he is able to use one of the radio’s controls to switch between the different filter types.Īnother thing about Gareth’s project is that it uses a Teensy 3.2. I haven’t really looked at the code yet, but Gareth’s program will switch between a CW filter, a SSB filter, and a third type that I couldn’t make out from the video. ![]() It uses a pure javascript implementation of the Parks–McClellan filter design algorithm.” This tool generates the coefficients used by the Teensy program. The web page describes this tool as “a web application that generates linear phase, optimal, equal ripple finite impulse response digital filters. On the code and instructions page, Gareth links to a tool called TFilter. Gareth notes, “ The project is easily modified to run on other rigs or could be fitted inside an amplified speaker.” The latter is what I had in mind. A video showing the Teensy DSP in action.But most of the Arduino framework has been ported, so migrating your projects is pretty straight forward. Instead of an Atmel microntroller the Teensy platform uses ARM Cortex chips since revision 3.0. It was posted by Gareth, GI1MIC, and includes a couple of links to an open-source project that uses an earlier version of the Teensy to implement an audio DSP add-in for the FT-817. Luckily there is a powerful Arduino-compatible hardware called Teensy to the rescue. Well, yesterday, my friend, Quentin, KD8IPF, sent me an e-mail posted to the 817ND mailing list. Of course, I haven’t yet done anything with it. So, I joined the Kickstarter, and in due course a Teensy 3.5 arrived in my mailbox. “Hmmmm,” I thought to myself, “I bet these processors could do some digital signal processing.” I got really interested when I read about the Teensy Audio Library, which is a toolkit of dozens of audio processing components. The Teensy 3.5 Arduino-compatible microcontroller features a 120 MHz ARM Cortex M-4 processor with a floating point unit. The designer, Paul Stoffregen, bills his Teensies as “powerful microcontrollers for making awesome DIY electronic projects.” The Teensy 3.5 uses a 120 MHz ARM Cortext M-4 processor with a floating-point unit. Last fall, I ran across the Kickstarter for the Teensy 3.5 and 3.6. ![]()
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