So you’ve got a cool/witty name for your band, a Soundcloud account, a 3D-printed Daft Punk helmet… so what could be missing from your road to stardom? The NeoTrellis M4 Kit Pack, of course!
The NeoTrellis M4 is an all-in-one USB + NeoPixel + Elastomer + Audio board. It’s powered by our new favoritest-chip-in-the-world, the SAMD51, a Cortex M4 core running at 120 MHz. This chip has a speedy core with CircuitPython and Arduino support, hardware DSP/floating point, dual DACs (more on that later!) and all the goodies you expect from normal chips like I2C, ADC, DMA, etc. It has a roomy 512KB of flash and 192KB of SRAM so it’s great for CircuitPython, we added a full 8MB flash chip so tons of space for files and audio clips.
The native USB port can turn it into a MIDI USB device if you like – currently that’s only supported in Arduino. Tether it to a computer or tablet, if you like. Or use it in standalone mode, as long as its powered from a USB power plug, it’ll run whatever firmware is burned into it.
OK so you’ve got this big brain, but now you need inputs and outputs! There’s a 4×8 grid of elastomer button pads with a NeoPixel nestled in the center of each one. You can read any/all button presses simultaneously thanks to the fully diode’d matrix, and also set each button color to any of 24-bit colors. (We’ve even got some DMA Arduino code for the NeoPixels so that they won’t take up any processor time.) The elastomer buttons are translucent so they glow beautifully when lit.
Time to make some noise! We picked the SAMD51 mostly because its got that dual DAC – that’s two 12-bit, 500KSPS ‘true analog’ outputs and we connected them to left and right on a standard headphone jack. Since the DAC pins are also ADC pins you could also use the left/right for audio line level input if you so choose. You’re not going to get audiophile-quality outputs from two 12-bit DACs but you can certainly play audio clips and make beeps and bloops.
And if you want to have some audio inputs, we have you covered. The 4th pin on the headphone jack is for microphone or line in. If you have a classic ‘mobile phone headset’, the electret mic will go through an amplifier into an ADC pin. Again, it’s not audiophile quality (we’re talking about an electret mic here) but you can do audio recording and filtering on the mono input. The raw un-amplified mic input is also connected to a DAC so you can read button presses on headsets that have a resistor-selector for their buttons, or some other 3.3V-max analog signal.
To add more interactivity, a precision triple-axis accelerometer from Analog Devices, the ADXL343, is included as well, and provides sensor information on tilt, motion, or tapping. Great for adding another dimension of data input in addition to the button pads.
Finally, a 4 pin JST hacking port is available for extra add-ons. It’s STEMMA and Grove compatible, and provides GND, 3.3V power, and two pins that can be used for I2C, ADC, or a UART. So connect some other sensor, or read stereo audio in, or maybe hack together a MIDI port. Whatever you like!