We’ve seen the Raspberry Pi Pico in some pretty cool form factors. From Pimoroni’s little one 2040 for Adafruit RP2040 Feather via Arduino RP2040 Nano Connectionwe saw a lot of best raspberry pi pico boards cross our workbench. But Solder Party’s RP2040 stamp is something a little different.
This $12 one-inch square board looks like a postage stamp, but in the center is the familiar RP2040 SoC, along with 8MB of flash storage and a full set of GPIO pins forming a perimeter of slots around the board. .
Solder Party’s RP2040 pad is designed for those of us who want the power of the RP2040 in our own custom PCB, but don’t want to have to solder small pitch electronics. Drop it into your own custom robot, machine learning, computer vision project and you’re good to go.
With that in mind, we soldered our test unit to the $6.50 RP2040 Stamp carrier board and settled in for an afternoon of testing with this rather curious board.
RP2040 Buffer Specifications
|system on chip||RP2040 microcontroller|
|Dual-core Arm Cortex M0+ processor, flexible clock running up to 133MHz.|
|264 KB of SRAM and 8 MB of integrated flash memory|
|GPIOs||All 30 GPIO pins|
|2 x Spinnaker|
|1 x WS2812B NeoPixel (GP21)|
|LiPo power and charging circuit|
|LDO 500mA 3.3 Low Dropout Regulator|
|SWD Breakdown (Debug)|
|GPIO pins are 2mm pitch|
|Dimensions||1 x 1 inch (25.4 x 25.4 mm)|
Using the RP2040 buffer
The one inch square form factor of the pad, along with the notches around the perimeter of the board mean that this board is intended for use in a custom PCB. Something that Solder Party is well aware of and provides fingerprints for use with popular PCB design applications. These footprints are intended for surface mounting and through-hole soldering.
The easiest way to connect your RP2040 pad to a custom PCB is to match the footprint. This will line up the RP2040 Stamp castellations with pads on your PCB, then using a blob of solder we can join the two together.
If you want to use the RP2040 pad with a breadboard, things get a little tricky. The board’s preferred 2mm pitch means we can’t just lay this down on a breadboard. Of course, we can buy header pins and 2mm breadboards, but we have to factor that into our project costs. That said, a 2mm pitch was the right fit for our testing as it gives us all the GPIO pins present on the RP2040 and keeps the board small. The pins are laid out logically, starting at 0 and moving counterclockwise around the perimeter of the board.
Speaking of GPIO pins, the RP2040 Stamp has a few built-in extras. On the underside of the board we spotted breakouts for USB (D+ and D-), battery, and serial debug (SWCLK, SWDIO) that allow the board to work with the support board, but more importantly, it does allows to work with your custom table. Clever stuff!
For our test, we used the RP2040 buffer carrier board, a board that has some similarity to the Arduino Uno form factor and breaks out enough, but not all of the GPIO pins. Soldering the RP2040 pad to the carrier board was simple. We just had to make sure we had the right orientation before we started.
Once soldered, we connected the board to our machine via the USB-C port. Great to see another board using USB-C. The connector is rugged and virtually foolproof. We’ve updated to the latest version of CircuitPython, but since it’s an RP2040, we can use one of many programming languages. For this review, we’re going to stick with CircuitPython as it provides the best way to access all of the features of the board. On the CircuitPython homepage there is a special version of CircuitPython for the RP2040 Stamp.
We started with simple things. Could we blink the user LED, located just behind the DC power jack? The answer is of course yes. The user LED is wired to the GP20 and it only took a moment to write a simple script to flash the LED 100 times with a 0.1 second delay.
This simple test confirms that our Stamp RP2040 is properly soldered, and that we can communicate with it.
We did two more tests. The first was an external LED connected to the GP9, then we added a 10K Ohm potentiometer and changed the code to use the potentiometer as a raw switch. The switch triggers the on/off LED depending on the voltage read on analog pin 0. This test also allowed us to try the carrier board’s 7 – 12V DC barrel jack with a 9V PP3 battery. It went perfectly, and our code worked independently of USB power and a computer.
We also tested the carrier board’s onboard LiPo charging system, which provided a constant 600mA charging current to the 2000mAh battery. When the USB power source was removed, the board continued to function, running from LiPo.
Now on to the more difficult things. The carrier board supports Stemma QT, Qwiic, and QW/ST compatible boards, making it easy to interface with compatible devices. We dug through our bit box and found the venerable MPR121 capacitive touch board. This is our reference board for testing Stemma Qt / Qwiic / QW/ST connections because it is so simple to use.
Touch one of the numbered entries and it will print which one was touched and the current state. We put the code on the RP2040 buffer and then saved in code.py. That’s when we saw an error in the Python shell; something was missing.
Normally we import the Plank CircuitPython library to allow access to GPIO pins. For the RP2040 buffer, we needed to modify the import to use import stamp_carrier_board as a board. Stamp_carrier_board is a board-specific version for the RP2040 buffer. With that done, we saved and ran the code and everything checked out without any issues.
RP2040 Buffer Use Case
If you just need a breadboard compatible RP2040 board, then go get one of the best RP2040 cards. If you want to build your own RP2040 powered boards with custom PCBs, then Solder Party’s RP2040 pad is for you. Offering the footprints for popular card design apps is a smart move. This means that card designers can simply continue creating a project powered by RP2040 Stamp.
It’s not for everyone, but if you need the power of the RP2040 in a handy little package, then the RP2040 Stamp is for you. Ease of use, large form factor and a full GPIO make it a great way to create your own boards.
There’s an alternative, in the form of Pimoroni’s PGA2040 that offers a similar, slightly smaller experience. The PGA2040 has a 2.54mm pin pitch which means it can be used with breakout headers, but due to the high pin density it is not high speed compatible .
In our opinion, we think Solder Party’s offering is the better of the two, and that takes the 2mm pin pitch into consideration. We get a small board that breaks all the tricky wiring down into a much easier to solder package.