Thermal transfer paper DIY PCB test

Hi!
Some days ago I've got another pretty thing from Aliexpress: thermal transfer paper for PCB DIY.
After making some boards with 0.5mm traces with perfect quality, I decided to test capability of this paper and my printer (HP 1020). Main goal was to create home made PCB with 0.25mm traces and 0402 components =)
So here is a test board after etching in ferric chloride:

Left side: 0.33mm traces with ~0.3mm spacing. Right side: 0.25mm traces, ~0.2mm spacing, one 0603 and two 0402 components.

Let's have a close look (click for large images):

Close to perfect for home DIY! Link to Ali store if you're interested.

MAX7219 Library for 8-bit AVR

Hi friends!
Yesterday I've got my 32x8 matrix module from Aliexpress.
I don't understand need of C++ usage in low-memory chips (most of all I'm using Attiny2313, Atmega48 and Atmega88), so I decided to write my own C library for 8-bit AVR's.

Because I have matrix module, digit mode for MAX chips was not tested.

Features:

• Per-pixel draw
• Simple buffer scroll function
• String render (latin+cyrillic variable character width font included)
• Easy to implement text scroll
• Support for both Flash and RAM string sources

Please note: library uses alpha version of AVR SPI library based on Stefan Engelke's code (included). Software and USI SPI not tested.

Here is Atmel Studio 6.2 project:

Download from Google Drive