ePaper 4.3" (800x600) with UART interface
ePaper is the display interface which is more and more popular thanks to zero power consumption and also price which is lower than before a few months and years. ePaper display is taking the energy only in the moment when the display is refreshed. Otherwise the power consumption is zero.

Online C compiler and debugger - how to speed up the development of your C code
I'm sure that you encountered with the situation when your code or part of your code didn't work as you wanted - operation with a few pointers, logic operations, conditions, parsing of value from long array etc. If you have modern microcontrollers and development board which supports debugger (e.g. STM32 and Nucleo, Discovery) you can easily step (debug) your code in debugger. If you don't have debugger, how do you follow values, variables? Are you using UART? Or LCD?

Helpful tools for makers
Whether you design own devices sometime you will need some tools for easier development of something. Maybe you made something what could be helpful for other makers. Maybe your helpful tool doesn't sell. This article shows what everything could be helpful and how change useful tools to better tools.

Etching of PCB - faster, cheaper, safer
My ferric chloride was saturated and so couldn't etch. I looked for equivalent, but I found something so much better. I found very interesting video here. But some etching bath are very unstable or/and dangerous - e.g. hydrogen peroxide with hydrochloric acid - it excludes chlorine.

Eagle tips and tricks
HOW TO create a bus, adding copper ground pour in Eagle, adding pin power operational amplifier, move text/name/value components, increasing pad (pin) of component in Eagle