Circuit Playground Express Serial Communications

by Anne Barela

published August 14, 2018, last updated September 30, 2024

posted in MakeCode Circuit Playground/ Express Programming/ MicroPython / CircuitPython

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Intermediate

Project guide

USB Converter Connections

Using the Adafruit USB Serial to USB Cable

The red wire is not required and should not be used if you power the board from a battery or the native USB port.

Note you can use the +5 volts out on the external cable and board to provide power to the Circuit Playground Express on the Vout pad. The Circuit Playground Express should not draw more than 200 milliamps or so unless you use the NeoPixels where the current could rise above 450 milliamps which may be quite high. Check any device's specifications if you have custom needs or use an external power source and do not connect the converter's +5 out to the board.

Note the color connections: The White Alligator Clip on RX goes to the GREEN wire on the converter, the Green Alligator Clip to the WHITE wire on the converter. That is TX -> RX and RX -> TX for serial between devices.

If you are looking to establish a serial connection via the Adafruit USB console cable #954, the connections are shown above. This diagram shows using the USB cable power for the Circuit Playground Express (the red wire). If the console cable is plugged into a computer, the red wire has +5 volts and can power the Circuit Playground Express if connected to the Vout pad. If you plan to power the Circuit Playground Express via battery or USB power via the onboard USB connection, do not connect the USB serial converter cable red wire.

The signal wires RX and TX are 3.3 volt "TTL" levels so they are safe for Circuit Playground Express.

For computer drivers for using the USB port from the USB converter cable:

If you are running Windows 7/8/10 etc, check this tutorial page with links to drivers for both PL2303 and CP2102
If you are running Mac OS X, check this tutorial page with links to drivers for both PL2303 and CP2012
If you are running Linux, drivers are already included in the kernel, no need to install anything!

In Windows, you will see the following icon appear in the Control Panel -> Devices and Printers view:

Using the Adafruit CP2104 Serial Communications Board

Above shows the connections for the Adafruit CP2104 Serial board #3309. The headers are not soldered in to get a better view of the board markings. This diagram assumes you are using USB or battery power for the Circuit Playground Express. The signal wires RX and TX are 3.3 volt "TTL" levels so they are safe for Circuit Playground Express. The ground wire provides an electrical return path so is necessary.

For Windows, the USB driver is in Windows Update, Mac OS drivers are here, Linux does not need a driver.

What do these connections do?

These connections turn a serial connection between the Circuit Playground Express (via the hardware serial TX and RX pads) to the cable and board which have chips which convert the TTL serial into USB serial communications.

Why not just use the Circuit Playground Express USB port?

1) The software support for USB on the Circuit Playground Express was discussed earlier - there are some limitations on its use in various languages that may not be present with an external board.

2) Sometimes you need more than one serial connection.

Can I program the Circuit Playground Express via an external USB connection like the ones shown?

Nope! This is only for debugging output from MakeCode or CircuitPython

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