Interpreting Brainf*#k on an AVR

brainfuck

We won’t call it useless, but we will ask why [Dan] wrote a brainfuck interpreter for the AVR

It’s not generating code for the AVR; think of it more as a bootloader. To run a brainfuck program, [Dan] uploads it to the EEPROM inside his ATMega32, after which the microcontroller takes over and starts performing whatever instruction the brainfuck program tells it to do. Because the whole thing runs off the EEPROM, the code size is limited to 1022 bytes. Enough for any brainfuck program written by a human, we think.

As for why [Dan] would want an AVR to build an interpreter for a language that is nearly unreadable by humans, we honestly have no idea other than the common, ‘because it’s there’ sentiment. There are some pretty cool projects out there that use brainfuck, including this genetic algorithm software developer. Right now, though, blinkey LEDs are enough to keep us happy, so you can see a video of brainfuck doing its thing on a LED bar display after the break.

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A JavaScript interpreter for ARM ‘micros

When programming a microcontroller to do your bidding, you only have two choices. You could write your code in a proper language such as C and cross-compile your source into a piece of firmware easily understood by a micro. Alternatively, your could load an interpreter on your microcontroller and write code via a serial connection. Interpreters are a really fast and easy method to dig in to the hardware but unfortunately most microcontroller interpreters available are based on BASIC or Forth.

[Gordon] figured it’s not 1980 anymore, and interpreters for these relatively low-level languages aren’t a good fit with the microcontrollers of today. To solve this problem, he created Espruino, a JavaScript interpreter for the new batch of ARM development boards that have been cropping up.

Espruino is designed for the STM32VL Discovery board, although [Gordon] plans on porting his interpreter to the Arduino Due when he can get his hands on one. Installation is as easy as uploading any other piece of firmware, and even though [Gordon]‘s STM32VL doesn’t have a USB port for a serial terminal, it’s a snap to connect a USB to TTL converter and get this interpreter working.

Espruino isn’t open source yet, only because [Gordon] would like to clean up his code and write a bit of documentation. He’d also like to make Espruino profitable so he can work on it full-time, so if anyone has an idea on how [Gordon] can do that, leave a note in the comments.

BASIC for some beefy AVR chips

klBASIC is a BASIC interpreter written in C for AVR microcontrollers. [Karl Lunt] developed the project based on an assembly language BASIC interpreter for 68HC11 chips written by [Gordon Doughman]. The transition from assembly to C bulked up the code, so you’ll need a beefy AVR chip in order to store all of it.

The idea is that one AVR chip can run BASIC with just a serial monitor. But like this Arduino BASIC interpreter build, it would be a snap to run this with a keyboard and small LCD screen. We see binaries available for several different AVR devices including ATmega128, ATmega1284, and Xmega128. They range from 1.5k to 16k of program memory. We didn’t find a link to the source code (just these precompiled files) so we inquired with [Karl] to see if that is available. He’s reluctant to release the code because it’s “pretty much a mess” and doesn’t live up to his normal standards. If he codes for a living we can see how that may be embarrassing. If you’d like to lend a hand cleaning up the code, let him know by leaving a comment here and maybe he’ll release it for that purpose.

We find this interesting, but it’s tough to get excited about building one of our own. If this has inspired you, we’d love to hear some of your plans in the comments after the break. Perhaps we’d be prodded into another programming adventure based on your enthusiasm.

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