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TM1638NR: a small TM1638 library
This header-only library takes about half the code size of the smallest library I could find  (TM1638lite) before I wrote my own. https://github.com/nerdralph/TM1...  
Thursday, 16 April 2020 - 00:42
debugSerial: a tiny asynchronous serial output library
A small subset of the most common Arduino print methods are supported.  The primary design goal was the smallest possible code size, for use on tiny AVRs like the t13. https...
Wednesday, 15 April 2020 - 00:07
trying to get avr-gcc to optimize static variables
With -Os -flto, avr-gcc 5.4.0 fails to optimize statics that are only ever referenced locally. i.e.   #include <avr/io.h> static uint8_t count = 0; int main(void...
Tuesday, 14 April 2020 - 15:03
fastest ever AVR bit-bang UART: 2 cycles/bit
I'm not sure what it's good for, but I wrote a bit-bang UART that runs at half the AVR clock rate.  I tested it with an ATtiny running at 4Mhz, and had no receive errors at...
Wednesday, 8 April 2020 - 20:23
strange t13A from AliExpress
I've  recently been doing a lot of testing on a t13A that I bought a few years ago.  I had done some basic testing (blink an LED) when I first received it to confirm I...
Wednesday, 25 March 2020 - 16:44
2Mbps bit-bang UART on a 10Mhz ATtiny13
Most of the AVR bit-bang UARTs I've written require a minimum of 7 cycles/bit (without unrolling).  Yesterday I had an idea to cut the loop time to 5 cycles, which allows for...
Monday, 23 March 2020 - 16:04
detecting compile-time integer constants with gcc
I'm trying to detect compile-time integer constants so I can have some code fail with an error when given an argument that cannot be determined at compile time. ...
Thursday, 19 March 2020 - 19:21
gcc unwanted loop hoisting?
Compiling with -Os, avr-gcc 5.4.0 seems to be making unwanted speed optimizations at the cost of space.  Here's some sample code and the resulting asm: void sput(char* s...
Saturday, 14 March 2020 - 22:28
more avr-g++ stupid optimizations (integer promotion?)
avr-gcc 5.4.0 (also tested 4.9.2), -Os -flto, compiled as C uint8_t printHex(uint8_t value) { dbgtx(nibbletohex(value>>4)); 68: 28 2f mov r18, r24...
Sunday, 1 March 2020 - 15:31
spike filter details?
Does anyone have details (hopefully a schematic) of the reset spike filter?  I've been testing ADC0 on 8-pin tinies like the t13 and t85, without disabling reset.  I'm...
Thursday, 20 February 2020 - 23:00
unconnected pins usually don't float
Over the years I've read lots of comments about floating input pins.  I've usually found that unconnected pins read as zero, but never did any thorough testing.  A few...
Sunday, 16 February 2020 - 22:42
Building a better bit-bang UART
I've written a blog post describing asynchronous serial UART communication and my bit-bang UART library, picoUART. http://nerdralph.blogspot.com/20...  
Thursday, 13 February 2020 - 02:08

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