Obsessed with computers since 2002
A picture is worth a thousand LLM prompts: Horizontal value is the input value x for cosf(x), ranging from 0 to 2π. The orange line shows the result of evaluating cosf(x), which looks exactly as expected. The blue line shows the time it took to evaluate cosf(x) for each x, in nanoseconds. I discovered this […] The post A few spikes in Pico cos() appeared first on Quentin Santos .
I had a few hours of “fun” figuring out why my RP2350 could use my ILI9341 display, but not the ST7796 one. To be more specific, displaying stuff with the first display worked flawlessly, while the ST7796 would display a single frame correctly, and then glitch. Depending on the exact code running, the glitches would […] The post The RP2350 is too fast appeared first on Quentin Santos .
Context I have a RP2350 and an SSD1306 module. I want to use the former to display stuff on the latter. The most common modules are connected over I²C: The simple way to use such a display looks like this: Basically, to refresh the SSD1306, we need to send an I²C message with a command […] The post Asynchronous I²C in C appeared first on Quentin Santos .
Following my adventures (part 1, part 2) with the RP2350-USB-A, I took another look at the alternatives. Specifically, I am looking for a cheap dev board with two full USB ports (1 device, 1 host), that could be easily programmable, and would be production-ready for hobbyist projects (if you’re a professional, you’ll just manufacture your […] The post (No) alternatives to the RP2350-USB-A appeared…
What’s better for New Year’s Eve than debugging some USB hardware issues? In my previous article, I explained how the design of Waveshare’s RP2350-USB-A can make the USB-A host connector incapable of detecting certain USB devices, and of any hot-plugging. The solution was to desolder R13, a pull-up resistor on D+: With this fix, my […] The post The RP2350-USB-A cannot see devices disconnect…
tl;dr: you need to desolder R13, the resistor closest the pin 6 of the board, as indicated by the red arrow in the cover picture of this article Context I am currently toying around with emulating a USB device. However, I also wanted to be able to plug a keyboard in, so I needed a […] The post Fixing the RP2350-USB-A not working as USB host appeared first on Quentin Santos .
The previous series of articles about UART was initially motivated by an error I was getting when using the ESP-Prog. I could have jumped straight to the conclusion, but I took the time to really understand what was going on, and we are finally reaching the end of this investigation. Connecting to “real” UART again […] The post The serial TX path seems to be down appeared first on Quentin Santos .
The mystery In the previous article, I briefly mentioned a slight difference between the ESP-Prog and the reproduced circuit, when it comes to EN: Focusing on EN, it looks like the voltage level goes back to 3.3V much faster on the ESP-Prog than on the breadboard circuit. The grid is horizontally spaced at 2ms, so […] The post Transistors in reverse and redundant circuits appeared first on Quentin…
In the previous article, we peeked at the reset circuit of ESP-Prog with an oscilloscope, and reproduced it with basic components. We observed that it did not behave quite as expected. In this article, we’ll look into the missing pieces. An incomplete circuit For a hint, we’ll first look a bit more closely at the […] The post The missing part of Espressif’s reset circuit appeared first on Quentin…
I recently discussed how Espressif implements automatic reset, a feature that lets users easily update the code on an Espressif microcontroller. There are actually more subtleties than a quick look would suggest, and I spent a fair bit of time investigating them. This article and the next two present (The missing part of Espressif’s reset […] The post Reproducing Espressif’s reset circuit appeared…