Tag Archives: Pico

Fun with FreeRTOS and the Pi Pico: interrupts, semaphores and notifications

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One of the reasons why an embedded application developer might choose to build their code on top of a real-time operating system like FreeRTOS is to emphasise the event-driven nature of the application. For “events” read data coming in on a serial link or from an I²C peripheral, or a signal to a GPIO from a sensor that a certain threshold has been exceeded. These events are typically announced by interrupting whatever job the host microcontroller is engaged upon, so interrupts are what I’ve chosen to examine next in my exploration of FreeRTOS on the Raspberry Pi RP2040 chip.

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Further FreeRTOS fun with the Pi Pico: sizing up scheduling

FreeRTOS scheduling is hard in as much at can be difficult to decide how to configure it. I wanted to try and figure out the options.

The popular real-time operating system provides the configUSE_TIME_SLICING and configUSE_PREEMPTION as settings values. You can add them to your FreeRTOSConfig.h file Tasks themselves can be assigned priority values, and there are API calls to allows tasks to sleep, to yield up the CPU, and be suspended and subsequently resumed.

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How to use FreeRTOS with the Raspberry Pi Pico

While documenting Twilio’s in-development Microvisor IoT platform, I’ve been working with FreeRTOS, the Amazon-owned open source real-time operating system for embedded systems. Does FreeRTOS work with the Raspberry Pi Pico’s RP2040 chip? I wondered. It turns out that it can, and this is how you set up a very basic FreeRTOS project which also serves as a demo.

The RP2040-based project uses a Pico board and an extra LED
Running the RP2040 FreeRTOS demo app
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Pico USB serial communications with CircuitPython

My Raspberry Pi Pico-based Motorola 6809 emulator uses the RP2040’s built-in serial-over-USB functionality to receive machine code sent from a host computer. The 6809 and its support code is written in C, but can you make use of the same process under Python? Yes, you can, and here’s an easy way to do it.

Computer to display via RP2040 serial comms
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Build a Raspberry Pi Pico WiFi IoT Device

Last Summer, I explored using the Raspberry Pi Pico as the basis of a cellular IoT device. That done, I wanted to try out WiFi connectivity. To do so, I ordered a Pimoroni PicoWireless.

Weather updates, Pico style
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Raspberry Pi Pico development on the iPad Pro: almost, but not quite there

I recently upgraded my ageing iPad to a new iPad Pro 11. This has a USB C port, and I immediately wondered if I could use this to connect a USB C equipped Raspberry Pi RP2040-based device like the Adafruit Feather RP2040, and do development on the iPad rather than a Mac. The answer is a cautious ‘yes’, provided you can work to a very specific limitation: your RP2040-side application environment has to be CircuitPython.

CircuitPython code written on iPad, run on RP2040
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Program games on the Pimoroni PicoSystem

A wee while back I ordered a Pimoroni PicoSystem to try out. It’s a small handheld games console based on the Raspberry Pi RP2040 microcontroller, and it sports both classic joypad controls and a 240 x 240 16-bit colour display. I gave my first impressions in an earlier post. Here’s what I think after spending some time porting my Raspberry Pi Pico version of the 1980s 3D shooter Phantom Slayer to the unit.

Phantoms to be slayed on the PicoSystem
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First look: Pimoroni’s PicoSystem hackable handheld games console

I’ve had my eye on the PicoSystem, the Raspberry Pi RP2040-based games console platform, for some time. It surfaced back in the Spring and was long marked “coming soon”. But now it’s here, mine showed up yesterday while I was at work, and this morning I’ve been messing about with it.

PSP = PicoSystem by Pimoroni
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How to build a cellular IoT device with the Raspberry Pi Pico — part two, the code

In part one, I described an IoT demo setup based on the Raspberry Pi Pico and the Waveshare Pico SIM7080G Cat-M1/NB-IoT cellular add-on board, and wrote about some of the design goals. Now it’s time to implement that design with some C++ code: a host application, drivers for the modem, the HT16K3-based display and the MCP9808 temperature sensor, and some third-party libraries to decode incoming commands formatted as JSON and encoded in base64 for easy SMS transmission.

Pico + Waveshare cellular module = compact IoT development board
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How to build a cellular IoT device with the Raspberry Pi Pico — part one, the hardware

To turn the Raspberry Pi Pico into an Internet of Things (IoT) device, you need to add wireless connectivity. I thought I’d give it go, to see how straightforward it might be to connect the Pico to cellular networks and have a bare-metal app written in C++ run the show. For a modem, I chose to use Waveshare’s suitably sized Pico SIM7080G Cat-M1/NB-IoT.

Raspberry Pi Pico piggybacking on the Waveshare cellular board
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