Using something like a 74HCT14 (the HCT version not the HC version) has the added advantage that it can act as a level shifter too if powered from a 5V supply. Without some kind of buffer there is a risk that a faulty receiving device could draw too much current from your Pico. This will protect your 3V3 device in cases where it gets plugged into another device with a dodgy or faulty MIDI IN circuit.
two inverters in series) on the transmit side between the TX pin and the MIDI circuitry.
“Sum of all current being sourced/sunk into GPIO and QSPI pins” is 50mA total (RP2040 datasheet, Table 622).įor “robust” applications, it is recommended to use a buffer (e.g. “The amount of current a GPIO sources or sinks is dependant on the load attached to it.” (RP2040 datasheet, 5.3.3.5). The Raspberry Pi Pico isn’t totally clear on the subject of GPIO current limits, but as the above components are designed to implement at 5mA current loop, as long as the GPIO can support 5mA all should be fine. A 33Ω resistor is required to link to the 3.3V power and DIN pin 4 and a 10Ω resistor is required to link to the TX pin and DIN pin 5. The core difference being that the resistor values are different for 3.3V operation. This is detailed in the “(CA-033) MIDI 1.0 Electrical Specification Update ”: One thing to watch out for is that the Pi Pico has 3.3V signal levels, but there was a revision of the MIDI electrical specification that showed how to hook up a MIDI out port to 3.3V signals. If like me you find DIN connector pinouts confusing, then take a look at the MIDI Connections Cheat Sheet. Transmit (TX) is GP4, which is all I need for MIDI OUT. This is hooking up MIDI to the second UART port of the Raspberry Pi Pico, which can be found on GP4 and GP5 (pins 6 and 7). I could see the PCB flexing quite a lot when inserting and removing – so be careful, do it slowly, and try to lever it up by the plastic on the pins not the PCB itself if you can. That is a lot of pins to push into a breadboard, and even more when it comes to trying to pull it off again. 5-pin 180 DIN socket, 10Ω and 33Ω resistorsįirst a note of warning. One of the 3.3V compatible Ready-Made MIDI Modules or. If you are new to all this, see the Getting Started pages. Update Feb 2021: If you are after MIDI IN functionality, then see MIDI In for 3.3V Microcontrollers. Getting Started with MicroPython on the Raspberry Pi Pico. These are the key tutorials for the main concepts used in this project: I am not responsible for any damage to expensive instruments! Warning! I strongly recommend using old or second hand equipment for your experiments.
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