I recently got a nice batch of nrf24l01 modules dirt cheap (~55 cent per module). If anybody wondered if you could cost-optimize these modules even more… Well, turns out you can. They won’t be quite working, but who cares? A detailed analysis of what those folks actually ‘optimized out’ is just under the cut.
If you’re following my blog, you might’ve read my post about Dlink’s substandard engineering, and how I’ve got debian running on the damn thing. Well, since that time I’ve made a few improvements, namely:
BIG FAT WARNING: I take no whatsoever responsibility if you screw up your device following these instructions. Proceed at your own risk, use your own head. This will also void warranty, btw.
Since I’ve got some homebrew development boards ready, it’s time to get hacking.
I stocked on coffee and gave esp8266 SDK a deep dive this weekend. The code is really weird, lots of things are unknown, API is shitty, blobs all around the place. First of all, to make things clear – I’m not going to fix or do anything with AT-command firmware. It sucks. Period. Sucks so much it can’t even prove useful as a reference most of the times. So… we need a replacement.
This is what I’m working on and that is now, after a weekend of hacking is in early alpha stage.
Say hello to Frankenstein Firmware for ESP8266.
As you might have seen, I’ve made a few projects with PL2303HX, namely that little nifty esp8266 developer board. I plan to dive in esp8266 firmware development soon and my goal will be a nifty mysql client, so that I can run mysql queries via UART! The only bad thing (apart from eeprom never working, and occasional freezes that I’ve later fixed with a 10uF SMD capacitor) – I had to press the buttons to reset the ESP8266 module to bootloader mode. So I’ve made a ‘dark green evil sister’ twin of that red board with a little bit updated schematics:
ESP8266 took a hell of a time to arrive, so meanwhile I got a dev board ready. Nothing really too fancy inside – just a PL2303HX, a few LEDs, buttons and connectors… But I couldn’t resist making some nice artwork on the silkscreen:
The board is made using my usual tech involving a color laserjet printer, toner transfer machine, and and some urethane coating for durability. Now, it’s high time to port antares to support esp8266 CPU!
TL;DR; Ported Debian on Dlink DNS-327L with fresh kernel, mybranch’s here‘е. Inside stock firmware there lies madness!
Now, the long read:
You might have noticed that my dull engineering blog has been lagging recently, occasionally throwing the nginx 500 error. That’s because of the ongoing cursed hardware adventures I’ve been having for the past 2 weeks.
But let’s start from the very beginning, and it will be a very long story. It all began with an HDD crashing in my RAID-1. Since the motherboard serving as the NAS storage box was pretty old and laggy, I decided I would get a nice and shiny small NAS box as well. The criteria was simple: cheap, supports nfs, small, RAID-1 supported.
So I picked Dlink DNS-327L and a spare HDD, I knew the box might be a Debian/OpenWRT target once the warranty’s void. Having dealt with some dlink hardware in the past (or, better to say, raising that hardware back from the dead) I ditched the stock power brick and used my own. I wanted to live on stock for a few months, just to make sure that no hardware is faulty…
Yeah, you might remember my old one, well it sucked. So I got hold of a bunch of pogo-pins and being too lazy to lay out a proper board made this monstrosity with a bunch of wires and a hot glue gun. Works really reliable. And I finally have where to plug the LPT port to flash it!
As you might remember, buspirate is a pic24-based device with a pic24 + ft232 for usb connectivity. pic24 runs (according to datasheet) at clocks up to 32Mhz. The price tag for my bpv3 hardware was something around 30$ at places like seeedstudio.
uISP on the other hand is way cheaper and simpler and contains only an atmega8 + a handful of passive components. It’s less than 5$ worth of components (and board!) and was designed by me a very long time ago as a super-cheap ISP programmer/devboard. Something I can give out to students to get started in electronics. uISP has NO HARDWARE USB. It just uses vusb stack. Yep, simple as that. The clock is 12Mhz on most boards and for this test I also made a super-special version with a 20Mhz crystal.
Now, can this cute little thingie outperform a much faster buspirate with hardware serial interface IC? Turns out it can, after all!
It was a busy month, but I finally managed to find a minute and update the rf24boot. Yes, the very thing that can push firmware updates via nRF24L01 wireless modules. Along is a regular bunch of updates to rf24 library in antares. One of the big news I finally took some 20 minutes and layed out a proper programming dongle. Since I didn’t have a cheap stm32 with usb around, and stm32f103ret6 looked like an overkill for this purpose this dongle still uses avr, vusb, but has a 16M (20M is possible as well) crystal. The lengthy changelog’s under the cut, but it’s big.
