Do not mention tabs
05.03.2026 18:11
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Do not mention tabs
A coconut sapling growing on a tropical beach.
If you enjoy my work on 🏝️ Isle.Computer, FPGAs, and RISC-V, consider sponsoring me: projectf.io/sponsor/
You get early access to source code and blog posts, and I send you a newsletter every month or so. Plus, you help me bring these open-source projects to life. ☺️
Number guessing game. The user is asked to guess a number between 1-100 and is told at each step if their guess is too low or too high. Isle.Computer running in a Vertilator/SDL simulation window.
I've added more software to 🏝️ Isle.Computer; all handwritten in bare-metal #riscv asm.The number guessing game exercises a surprising number of low-level features. Source code (on temp branch): github.com/projf/isle/t...
Chapter 6 features the FemtoRV "electron" RISC-V CPU. This CPU can multiply and divide all by itself! That comes in handy when converting integers to and from strings, amongst other things.
I've also got a whole blog post on the #riscv mul and div instructions: projectf.io/posts/riscv-...
"Sorry, I think you mean 'portentous', often confused by those with poor taste."
Verilator/SDL simulation running Isle hardware and software. The screen contents read: Hello, this is Isle.Computer demoing Unicode read line in RISC-V assembler. Open source Verilog hardware and bare metal RISC-V assembler. :) We have block elements in the character ROM.
Over the weekend I worked on 🏝️Isle.Computer designs for chapter 6. I've now added the designs to a branch and you can already run the sim on your PC (Linux/Mac/Windows): github.com/projf/isle/t...
Please have a quick play and let me know how you get on. 🛝
Or if wolves, goats, and cabbages are more your thing: en.wikipedia.org/wiki/File:Wo...
An animation of the wolf, goat and cabbage problem crossing a river
Sometimes Wikipedia gives you more than you dared hope (animated PNG). en.wikipedia.org/wiki/River_c...
# rand_pseudo - return a pseudorandom number using lfsr # a0: start of range (unsigned) # a1: end of range (unsigned) # return: pseudorandom number # rand_pseudo: li t6, SYS_DEV # check range is positive: ensure a1 ≥ a0 bleu a0, a1, 0f # skip if already in correct order mv t0, a0 mv a0, a1 mv a1, t0 0: # determine range: a2 = a1 - a0 + 1 sub a2, a1, a0 addi a2, a2, 1 beqz a2, 2f # branch if full range (a2 wraps to 0) # rejection threshold to remove bias neg t1, a2 # 2^32 - range remu t1, t1, a2 # threshold = 2^32 % range 1: # sample lfsr and check threshold lw t2, LFSR_32(t6) bltu t2, t1, 1b # reject if bias value (try again) # create random number in range remu t2, t2, a2 # divide by range add a0, t2, a0 # add start of range ret 2: # sample raw lfsr output for full range lw a0, LFSR_32(t6) ret
Linear-feedback shift registers (LFSR) are a classic way to generate pseudorandom numbers. I've written a #riscv asm function to return a random number using my lfsr hardware. This is part of the next instalment of 🏝️ Isle.Computer.
I’ve been thinking about software on simple systems. How much it depends on trigonometry and randomness to give it life.
# sunshine on a rainy day
# makes my soul, makes my soul
# drip, drip, drip away
I found the old 35mm slide for the cover for Neuromancer and had it scanned in for your pleasure. Enjoy!
Sign in window of shop reads: !!!STOP!!! GIVING CATS !!!TREATS!!! DONT PUT HAND THROUGH LETTERBOX
This Hastings shop wants you to STOP! 🙀 Though I'm now thinking of @gossjam.bsky.social.
I searched for "gnu assembler directives" (without quotes) and the top match on DuckDuckGo and Google is: ftp.gnu.org/old-gnu/Manu...
Looks promising apart from the fact it's from 1994! Back when my computer was an Amiga 1200 and Linux 1.0 was released.
Current docs: sourceware.org/binutils/doc...
An image showing Scotland with Aberdeen Airport marked and a sunny spell symbol
After 21 days without sunshine, Aberdeen recorded its first sunshine since 21st January this afternoon 😎
It is rendered in hardware. The current design only has 128 8x16 glyphs in rom. I'm still working on how I handle the full GNU Unifont with a mix of full (16x16) and half-width (8x16) glyphs. I will share my findings.
Isle.Computer running on ULX3S dev board connected to computer monitor over HDMI. The text on the monitor reads: Isle.Computer Hello, hardware friends. Demos look better on a dev board :) Thanks to my sponsors.
And a quick lunchtime shot of 🏝️ Isle.Computer running on #ULX3S.
Simulation may be practical for software dev, but it feels so much better seeing it running on real hardware. This is #riscv asm decoding UTF-8 sent over UART to Isle hardware running on #fpga. Verilog and asm written by hand. 😊
Verilator/SDL simulation window on macOS reads: Isle.Computer Hello, this is a 115200 baud test on Isle Computer. We also have delete and carriage return. Next up there's buffered input with a fifo...
I'm beavering away on practical input and output with UTF-8 on Isle.Computer. Text is a wonderful thing in its own right and also decidedly handy for debugging. The designs for the next chapter aren't too far away. #FPGA
You might be thinking, but Flux, if this is Unicode, why aren't you showing some cool Katakana, a little Hangul, or an emoji?
Alas, there's more to do, including full-width characters for text mode and larger storage to hold GNU Unifont (we currently only have basic Latin and block elements).
Verilator/SDL simulation running on macOS. The window displays the following text in orange on a dark background "▚▚ Hello, World! UTF-8 UART ▚▚".
Unicode UART goodness for 🏝️ Isle #FPGA Computer.
SDL key presses to UART via C++, sent to Isle hardware running under Verilator. The Isle #riscv asm software decodes the UTF-8 for display, including ▚ (U+259A).
We get Unicode user input in Verilator using same mechanism as physical dev boards. ☺️
I'm trying trailing underscore style, though I am seeing this form of message quite a bit. 😅
error: use of undeclared identifier 'data_idx'; did you mean 'data_idx_'?
It's easy to make someone's day.
When someone shares something beautiful or cool they've made, don't just favourite, take 30 seconds to write a comment. ✍️
Trite? Yes. But we still need reminding.
Well that’s one way to lose these walking blues. Diamonds on the soles of our shoes.
What do C++ devs think of Google's convention of naming class data members with a trailing underscore? google.github.io/styleguide/c...
uint32_t cnt_ = 0;
This looks odd to me, but it's been a while since I've done much C++. Verilator simulation is giving me cause to get back into it a bit.
ULX3S PCB connected to computer monitor showing “Hello, World! This is an Isle FPGA Computer UART test.”
Work on 🏝️ Isle #FPGA computer input chapter continues. Here I’m testing UART with #ULX3S dev board.
“While the RISC-V specification provides strong security primitives… implementations consistently choose insecure defaults… The decisions vendors make today… will be baked into billions of chips we cannot patch.” #riscv #fosdem
fosdem.org/2026/schedul...
“While the tradition remains popular in the 21st century, studies have found no consistent association between a groundhog seeing its shadow and the subsequent arrival time of spring-like weather.” — Wikipedia
Saying a Makefile link command out loud is strange: "dash R dollar caret, dash O dollar snail..." 🐌
I guess that's an AT not a snail, but after the carrot (caret) I unconsciously chose to say snail.
A thoughtful and informative article from Wiki Education on LLM use in #Wikipedia: wikiedu.org/blog/2026/01...
“Our fundamental conclusion about generative AI is: Wikipedia editors should never copy and paste the output from generative AI chatbots like ChatGPT into Wikipedia articles.”
I realised I never posted a video of the advanced asm animation introduced in this chapter.
