RA8875 LCD Flash share with Arduino

Hi!
For some time I have fun with 7" LCD display from Waveshare built on RAiO RA8875 controller chip. One of RA8875 great features is DMA support to load images from onboard flash chip.
Real trouble that there is no way to reprogram flash chip after soldering it to board.
Thanks to Waveshare engineers made header for dedicated flash SPI interface! There is no need to solder flash chip to display PCB, you can connect it to this header.

Idea! RA8875 does not use dedicated SPI all the time, only while DMA transfer is active. So why not share flash chip between two SPI buses: RA internal and Arduino?

There are cool IC's: 74LVC1G3157, single analog/digital SPDT switches. So, almost all time flash chip is connected to RAiO SPI, but when needed, it can be switched to Arduino's SPI bus. Switch control pins are connected to Arduino's CS pin.

Fixing Arduino Due R3 not starting bug

Arduino Due is a cool board with ATSAM3X8E microcontroller. But R3 version has a bug: on first power-up (or if power was turned off for more than ~5sec) board mostly will not start, and you have to push "Reset" button to make your sketch work.
I have two R3 boards with same issue. And it's annoying to push button every time =)
Today I've tried to use voltage control supervisor to automate power-on reset process.

We need:

• MCP100-315 supervisor (I have some of them, another not tested)
• 1N4148 diode (MCP100 series have totem pole reset output)

Pros. of MCP100 series: cheap, TO-92 case available, and 350ms delay before reset pin becomes high.

So here it is:

Connections

First I tried to connect Vdd pin of MCP100 to 3.3V pin. But threshold was too little and in most case board was in reset state for infinite. I think that MCP100-300 will work fine with 3.3V.

Conclusion.
I've made this fix for all two my R3 DUE's. All of them now start OK.

P.S. People say this bug was fixed in a new version: R3-E.

DIY switch indicator light

Customized light indicator for wall switches.

Holes were made with a piece of tungsten carbide drill with engraving tool. After milling holes were filled with clear glue. LEDs are covered with pieces of opal diffusor and a piece of white thick paper (120 g/m2) for additional light scattering.

Switches control low-voltage signal, no mains voltage is applied. LED's are driven independently by light control unit.

Image Editor/Converter for embedded (MCU-based) projects

Hi! Some time ago I've bought Arduino Due board (based on Atmel SAM3X8E chip) and 4.3'' 16-bit color TFT display. When I started to code graphics output, I've found that existing picture tools not very handy for me. So I've made a helper tool for graphic conversion. After some time, I've decided to make this program open source and add some useful functions.

I've tried to make easy-to-use image editor/converter, and hope I succeeded.

PixelImage

works under Windows (Linux users, sorry...)

at SourceForge.net

If you find this project interesting, please feel free to leave comments and bugreports at sourceforge.

Analog audio via UTP twisted pair

Hi all! Every time I want to listen music from my collection in another room (ex. kitchen), I have to take my tablet, connect it to audio system and setup streaming over WiFi. It's boring.

But what about direct audio from sound card to another room without network transcoding? I know there are devices starting from low costs to high-cost multiroom systems. Not my choice. It is interesting for me to make some kind of "multiroom audio" by myself =)

Buck-Boost LED Driver (34063)

Hi all! Earlier this year I've made improved version of 34063 LED driver. This is combined buck-boost converter witout output voltage inversion. Now I have some time to describe it =)

Font Editor for embedded projects

Hi! I've started a new project: Pixel font editor for DIY embedded projects.

Features:

• Character map generator from any installed font with flexible options.
• Individual character editor
• A bunch of code export options:
• UTFT library support
• Array for Nokia 3310/1202 LCD's
• Customized array (byte,bit order, packed character data)

Take a look here:

at SourceForge.net

9V multimeter powered from single AA battery

Hi! Another 9V battery was dead in my 830 multimeter. I've used this situation to make some modifications. I have a lot of half empty AA and AAA batteries, so I decided to power up multimeter from 1.1V (fresh AA/AAA have 1.5V).

DIY solder smoke absorber

Hi! As you could note my hobby is electronics =) So solder station is my frequently used tool. Long time I've used it without smoke absorber. I think that it is really useful thing =) I had a choice: buy it or make it. Of course, the simplest way is to buy, but I'm not looking for simple ways).
So I've decided to make something like this:

Update: Device is complete =)

AM2320 library for AVR's without hardware TWI support

Hi! Some time ago I've bought several AM2320 sensors. They have I2C interface, so it is very easy to use them with AVR's that have h\w TWI support. But what about low-end MCU's without full TWI implementation (Tiny2313, Tiny24, etc.)?
First I tried to use USI module for TWI implementation. As for me resulting code was too "fat" for 2Kb FLASH and there was no need for full TWI feature support (the only TWI device in my project was AM2320).

After some time spent on datasheet reading and hardware testing I've wrote a C library for these sensors. Please note that AM2320_ReadData function writes raw data to variables. This notice is actual for negative temperature values, where 0x8000 bit is set.

AM2320 Datasheet