PicoKeyer is a CW keyer for the Raspberry Pi Pico that let's you to practice CW (morse code) in Desktop or Mobile browser that supports the Web MIDI API. PicoKeyer has many configurable options, including the key type, words per minutes rate, LED/GPIO output, MIDI parameters; all within your browser. The PicoKeyer also provides a USB MIDI interface that enables you to use any MIDI app of your choice to record or listen to your CW.
You will need a Raspberry Pi Pico based on the RP2040 chip and a CW key (straight or paddles). The Pi Pico is available in a variety of configurations, any of them should work. If you do not already have a Pi Pico, I recommend picking up either an original Raspberry Pi Pico or a Waveshare RP2040-Zero board as I have tested both. You can find the original Raspberry Pi Pico, Waveshare RP2040-Zero, or a clone from $3-10/ea on Amazon, Aliexpress, or at retailers like Micro Center. If you want to use the case design included in the waveshare_rp2040_case directory, you will need a Waveshare RP2040-Zero or clone.
In addition to the Pi Pico, you will also need a way to connnect your RP2040 to your key. Most keys use a standard 3.5MM (1/8") stereo jack, however bare wires will also work fine. If you want to use the standard 3.5MM jack, I recommend the Lsgoodcare headphone jacks in the link below.
Amazon Links (non-affiliate)
- Raspberry Pi Pico (Quantity 2) $10
- Waveshare RP2040 Zero (Quantity 3) $20
- Lsgoodcare 10PCS 3.5MM Female Headphone Stereo Jack
The Raspberry Pi Pico comes with breadboard-friendly header pins, so it technically is possible that you could assemble a PicoKeyer using breadboard. However, I recommend that you solder a 3.5MM jack or a 3.5MM headphone-style cable directly to the Pi Pico as this will give you the best result. If you have basic soldering skills, assembly should be a breeze.
The simplest configuration is a straight key as only two wires are needed. The common (ground) of the key should be wired to one of the Raspberry Pi Pico ground pins, while the other contact needs to be wired to any available GPIO pin. Take note of the GPIO pin number as you will need to set that pin in the settings.
| Pi Pico Pin | 3.5MM TRS Jack Pin |
|---|---|
| GND | Pin 1 / (sleeve) |
| Any GPIO | Pin 2 / (tip) |
Three wires are needed to connect a paddle key to the PicoKeyer. The common (ground) of the key should be wired to one of the Raspberry Pi Pico ground pins, while the other two contacts (left and right paddle) need to be wired to any free GPIO pin. Take note of each GPIO pin number as you will need to set that pin in the settings.
| Pi Pico Pin | 3.5MM TRS Jack Pin |
|---|---|
| GND | Pin 1 / (sleeve) |
| Any GPIO | Pin 2 / (tip) |
| Any GPIO | Pin 3 / (ring) |
Head over to Releases and download the latest PicoKeyer.uf2 firmware. Plug in your Raspberry Pi Pico and open the RPI-RP2 drive. If the drive does not appear, hold down the Boot button on the Pi Pico before plugging it it. Copy the PicoKeyer.uf2 file to the RPI-RP2 drive. Once the firmware has finished copying, open the PicoKeyer Browser App in a browser that supports the Web MIDI API to configure your PicoKeyer.
The PicoKeyer Browser App provides a USB MIDI interface and allows you to directly configure the PicoKeyer from your browser. You will need a browser that supports the Web MIDI API (note: Safari does not support the Web MIDI API). Plug in your PicoKeyer to a free USB port and open the PicoKeyer Browser App. The app will prompt you for permission to access MIDI Devices, once allowed the application should automatically detect the PicoKeyer. If detection was successful, you will see the Settings button.
Click on the Settings button to begin configuring your PicoKeyer. Choose the key type to continue.
Configure the values for the Words Per Minute, Dit Paddle GPIO, Dah Paddle GPIO. All other values can be left default. (note: Other GPIO pin modes are supported, but if you have connected your common wire to GND on the Pi Pico, you will want to leave it on Pull Up mode)
Once you are satisfied with your options, you can press Apply to test. If successful, pressing your key should produce a visual indicator in the black box. You can enable sound by clicking on the slider to hear a CW tone. If you are satisfied, press Save to save the settings to your Pi Pico's NVRAM so the settings will persist between reboots.
My favorite Pi Pico is the Waveshare RP2040-Zero, it's a minature version of the full size Raspberry Pi Pico making it great for compact builds with no compromises. The RP2040-Zero comes standard with USB-C and an onboard addressable RGB LED. If purchased in bulk, the RP2040-Zero typically sell for about $2 each which makes them an ever better bargain than the Raspberry Pi Pico. For the PicoKeyer project, I have designed a custom case and included the STLs in the waveshare_rp2040_case directory.
The assembly is pretty simple, just find two available GPIO pins (I recommend GPIO 3 and GPIO 29) and solder to a 3.5MM female jack (linked above). Before soldering, ensure that the jack is facing away from the USB-C port.
