STM32 Analog Converter Phase Noise

May 1, 2017 by Al Williams 13 Comments

[Avian] has been using STM32 ARM processors to sample RF for a variety of applications. At first, he was receiving relatively wide TV signals. Recently, though, he’s started dealing with very narrow signals and he found that his samples had a lot of spread in the frequency domain that he didn’t expect.

What followed was some detective work that resulted in a determination that phase noise was the culprit. But why? [Avian] took some measurements and noticed that the phase noise almost exactly matched the phase noise specification for the STM32’s phase locked loop (PLL).

Unfortunately, there didn’t seem to be a good way to avoid using the PLL without major changes to the rest of the circuit. However, it was quite the learning experience and something to be aware of when counting on built-in converters for high-accuracy measurements.

One of the best things about this post is the references to more information. There’s a great explanation of phase noise, as well as a specific application note about clock jitter and analog converters.

We’ve talked about phase noise in direct digital synthesis a few times. But usually, it is pretty obvious like when you are asking a CPU to double as an RF transmitter. [Avian’s] post was a bit more of a detective story.

PlatformIO And Visual Studio Take Over The World

April 7, 2017 by Al Williams 40 Comments

In a recent post, I talked about using the “Blue Pill” STM32 module with the Arduino IDE. I’m not a big fan of the Arduino IDE, but I will admit it is simple to use which makes it good for simple things.

I’m not a big fan of integrated development environments (IDE), in general. I’ve used plenty of them, especially when they are tightly tied to the tool I’m trying to use at the time. But when I’m not doing anything special, I tend to just write my code in emacs. Thinking about it, I suppose I really don’t mind an IDE if it has tools that actually help me. But if it is just a text editor and launches a few commands, I can do that from emacs or another editor of my choice. The chances that your favorite IDE is going to have as much editing capability and customization as emacs are close to zero. Even if you don’t like emacs, why learn another editor if there isn’t a clear benefit in doing so?

There are ways, of course, to use other tools with the Arduino and other frameworks and I decided to start looking at them. After all, how hard can it be to build Arduino code? If you want to jump straight to the punch line, you can check out the video, below.

Continue reading “PlatformIO And Visual Studio Take Over The World” →

Hackaday.io User Reviews Six STM32 IDEs

April 4, 2017 by Al Williams 52 Comments

One of the issues with getting started with any Arm-based project is picking a toolset. Some of us here just use the command line with our favorite editor, but we know that doesn’t suit many people–they want a modern IDE. But which one to choose? User [Wassim] faced this problem, evaluated six different options for STM32 and was kind enough to document his findings over on Hackaday.io.

Many of the tools are Windows-only and at least two of them are not totally free, but it is still a good list with some great observations. Of course, the choice of an IDE is a highly personal thing, but just having a good list is a great start.

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Open Source Firmware For A Cheap Programmable Power Supply

March 7, 2017 by Brian Benchoff 64 Comments

A few months ago, someone clued us in on a neat little programmable power supply from the usual Chinese retailers. The DPS5005 is a programmable power supply that takes power from a big AC to DC wall wart and turns it into a tiny bench-top power supply. You can pick one of these things up for about thirty bucks, so if you already have a sufficiently large AC to DC converter you can build a nice 250 Watt power supply on the cheap.

[Johan] picked up one of these tiny programmable power supplies. His overall impression was positive, but like so many cheap products on AliExpress, there wasn’t a whole lot of polish to the interface. Additionally, the DPS5005 lacked the ability to be controlled over a serial port or WiFi.

This programmable power supply is built around an STM32, with the programming pads exposed and labeled on the PCB. The changes [Johan] wanted to make were all in software, leading him to develop OpenDPS, a firmware replacement for the DPS5005. Continue reading “Open Source Firmware For A Cheap Programmable Power Supply” →

STM32 And FPGAs In A Tiny Package

July 11, 2016 by Brian Benchoff 18 Comments

Slowly, very slowly, the time when we don’t subject embedded beginners to AVRs and PICs is coming. At a glacial pace, FPGA development platforms are becoming ever more capable and less expensive. [Eric Brombaugh] has been playing around with both ARMs and FPGAs for a while now and decided to combine these two loves into a single board that’s capable of a lot.

This board is fittingly called an STM32F303 + ice5 development board, and does exactly what it says on the tin. There’s an STM32F303 on board providing a 32-bit CPU running at 72 MHz, 48 kB of SRAM, a quarter meg of Flash, and enough peripherals to keep anyone happy. The FPGA side of this board is a Lattice iCE5 with about 3k Look Up Tables (LUTs), and one time programmable non-volatile config memory.

The connections between the ARM and FPGA include a dedicated SPI port, and enough GPIOs to implement full-duplex I2S and a USART. Like all good projects, [Eric] has shared all the files, schematics, and BOMs required to make this board your very own reality, and has provided a few links to the development toolchains. While the FPGA is from Lattice’s ice40 family, it’s not supported by the Open Source Project Icestorm toolchain. Still, it’s a very capable board for ARM and FPGA development.

Hackaday Links: March 28, 2016

March 28, 2016 by Brian Benchoff 15 Comments

[Tom] sent this in to be filed under the ‘not a hack’ category, but it’s actually very interesting. It’s the User’s Guide for the Falcon 9 rocket. It includes all the data necessary to put your payload on a Falcon 9 and send it into space. It’s a freakin’ datasheet for a rocket.

A year ago in Japan (and last week worldwide), Nintendo released Pokkén Tournament, a Pokemon fighting game. This game has a new controller, the Pokkén Tournament Pro Pad. There were a few cost-cutting measures in the production of this game pad, and it looks like this controller was supposed to have force feedback and LEDs. If any Pokemon fans want to take this controller apart and install some LEDs and motors just to see what happens, there’s a Hackaday write up in it for you.

There are a lot of options for slicing 3D objects for filament-based 3D printers. Cura, Slic3r, and MatterControl are easily capable of handing all the slicing needs you’ll ever have for a filament 3D printer. For sterolithography (resin) printers, the options for slicing are limited. [skarab] just put together a new slicer for SLA that runs entirely in JavaScript. If anyone wants to turn a Raspi or BeagleBone into a network controller for a resin printer, here’s your starting point. [skarab] will be working on smoothieboard integration soon.

The STM32F4 is an extremely capable ARM microcontroller. It can do VGA at relatively high resolutions, emulate a Game Boy cartridge, and can serve as the engine control unit in a 1996 Ford Aspire. There’s a lot of computing power here, but only one true litmus test: the STM32F4 can run Doom. [floppes] built this implementation of Doom on the STM32F429 Discovery board to run off of an external USB memory stick. The frame rate is at least as good as what it was back in 1993.

The Oculus Rift has just come to pass, but one lucky consumer got his early. The first person to preorder the Rift, [Ross Martin] of Anchorage, Alaska, got his facehugger directly from [Palmer Luckey] in a PR stunt on Saturday afternoon. Guess what [Ross] is doing with his Rift?

ARM Board Transmits FM

March 16, 2016 by Al Williams 27 Comments

There is more than a casual link between computer people and musicians. Computers have created music since 1961 when an IBM7094 sang the song Daisy Bell (later inspiring another computer, the HAL 9000, to do the same).

[Vinod.S] wanted to create music on an STM32F407 Discovery board, but he also wanted it to play on his FM radio. He did it, and his technique was surprising and straightforward. The key is that the ARM processor on the Discovery board uses an 8MHz crystal, but internally (using a phase-locked loop, or PLL) it produces a 100MHz system clock. This happens to be right in the middle of the FM radio band. Bringing that signal back out of the chip on a spare output pin gives you the FM carrier.

That’s simple, but a carrier all by itself isn’t sufficient. You need to FM modulate the carrier. [Vinod.S] did the music playback in the usual way and fed the analog signal via a resistor to the crystal. With some experimentation, he found a value that would pull the crystal frequency enough that when multiplied up to 100MHz, it would produce the desired amount of FM deviation. You can see a video of the whole thing in action, below.

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