Category Archives: How To (Pi)

Arm Assembly on the Pi Pico: Mnemonics #2

A number of the Cortex-M0+ Thumb ops I covered last time update the core’s Program Status Register (PSR) based on the outcome of the operation. The ops that do so have an S appended to their mnemonics and they only work with the core’s ‘low’ registers, R0-7.

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ARM Assembly on the Pi Pico: Mnemonics #1

Last time, I covered the basics of doing ARM assembly programming on the Raspberry Pi Pico’s RP2040 microcontroller. Now it’s time to get to grips with the dozens of instructions to which the RP2040’s Cortex-M0+ cores respond.

ARM assembly instructions for the Raspberry Pi Pico's RP2040 chip
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Get Started with ARM Assembly on the Pi Pico

When I got my first microcomputer, I already knew Basic programming. My machine had a different Basic dialect from the one I’d learned at school, and there was a stack of graphics and sound functionality to get to grips with too, but it wasn’t long before I felt I’d mastered the high-level stuff and that it was time to move on to machine code. That’s how I’ve come to feel about the Raspberry Pi Pico’s RP2040 chip. The time’s right to learn ARM assembly programming on the Pico.

The Raspberry Pi RP2040 chip
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Fun with FreeRTOS and the Pi Pico: timers

I made use of FreeRTOS’ timer functionality in the most recent post in this series, but I didn’t go into detail because the post was focused on other features. It’s time to address that deficiency. Today I’m talking about timers.

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How to do DNS over HTTPS on a Raspberry Pi

Last year, at the recommendation of a work colleague, I grabbed one of my spare Raspberry Pi 4s and installed the DNS proxy and content blocker Pi-Hole. It’s now handling all the DNS queries on my home network. Recently, I upgraded my Pi-Hole server to make its DNS requests over HTTPS.

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

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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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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How to send data to a Raspberry Pi Pico via USB

Do you need to transfer data to and from a Raspberry Pi Pico, or similar RP2040-based board, connected to your computer by USB? Here’s a neat way to achieve it without any tedious mucking about with the USB stack. Apart from a couple of questions on the Raspberry Pi Forum, there’s not much in the way of documentation, so here’s a write-up.

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