Arduino is also more mature now as a platform – there are many hardware options to suit different designing requirements. Sparkfun’s Arduino Pro series appealed to me and got me thinking that maybe I could switch (or rather, upgrade) to an Arduino-based environment for my RetroTAC project. Since the hardware is ATmega and the coding is similar to C, it’s not a big leap or a start-from-scratch kinda thing – more of an evolution.

So last week I bought an Arduino Pro 3.3v/8MHz unit from Sparkfun and on the weekend I set about getting it going.

I soldered male headers to the port pins (later realising that Arduinos normally have female headers, but oh well!) and jumpered up my USB-to-TTL serial adapter to the programming port pins. For power I will be running the RetroTAC from a 3.7v Li-Ion battery so I soldered jumper wires to the empty shell of a StarTAC where the flat power jack comes out, and hooked it right into the BATT of the Arduino.

At first the Arduino software gave me an error:
avrdude: stk500_getsync(): not in sync: resp=0x00
avrdude: stk500_disable(): protocol error, expect=0x14, resp=0x51

Which I found was more than likely related to the programmer being unable to reset the Arduino hardware before attempting to upload my sketch.

There’s a break in the trace (intentionally, but who’s intention and for what purpose I don’t know) which doesn’t link the RST pin on the PROGRAM header. I wired the USB adapter’s reset line to RESET on the Arduino and had the Blink ‘Hello World’ sketch running within minutes.

What I discovered was that the keypad, LCD and LCD controller are all on one board. It looks as if I could basically just ‘replace’ the mainboard and keep the existing keypad board if I can work out how to interface to the LCD’s controller IC.

Handily, the IC is labelled clearly with its model number: SED1530DAA.

Some googling reveals several versions of the datasheet for the SED1530, some more useful than others. Basically it is a “single-chip LCD driver for dot-matrix LCDs” by Epson, supporting parallel or serial (seems to be an input-only SPI bus) communication.

I’m in for a bit of work to interface to it, both physicaly and electronically, but if I succeed I’ll be able to write a driver to use the original screen hardware in my RetroTAC!

Any tips, theories, ideas or comments are welcome.

Today’s result: my little Atmel ATmega8 is telling the 4D Systems uOLED-160-GMD1 where to go! Or rather, what to say.


Using the ATmega’s USART hardware serial port, controlled in software by some USART routines written by Mihai Galos, I wrote a subroutine based on the OLED’s user manual entry for writing strings of ASCII text to the screen.

UOLED_fstring('s', 0x00, 0x00, 0x02, 0xFF, 0xFF, "Hello Interwebs");

The above is the line in the main code that sends the options to the subroutine. I’ve just realised while writing this that the first variable ’s’ is actually not necessary as the subroutine is specific for that command.

void UOLED_fstring( unsigned char cmd, unsigned char col, unsigned char row, unsigned char font, unsigned char msb, unsigned char lsb, unsigned char *c )
{
USART_Transmit(cmd);
USART_Transmit(col);
USART_Transmit(row);
USART_Transmit(font);
USART_Transmit(msb);
USART_Transmit(lsb);
sendString_USART(c);
USART_Transmit(0x00);
}

The above is the subroutine. As mentioned, the first line ‘cmd’ is actually redundant and I will change it to always send ASCII ’s’ / 0×73 which is the OLED’s command to print a string of formatted text.

Next up, I’ll expand this to display a short demo menu of options and code the keypad input to control the display – giving the basics of a User Interface.

I’ve also made a forum to foster discussion about my projects and whatever anyone who joins wants to talk about! Running on phpBB3, check it out at http://sniffingcrayons.com/debounce.

The USB converter came last week (after the wrong part was sent in May. Sparkfun were quick to correct this and I appreciate their excellent service) so I flashed the uOLED to its latest firmware and set about trying to communicate with it with my ATmega8.

Once again no success after two nights of poking about and checking & double-checking code, so I did some reading and got some ideas about why other people have had issues. Most of them relate to something wrong with the serial connection causing the auto-baud feature to not correctly ‘lock on’ to the serial signal. You see, the uOLED serial interface can run at serial speeds between 300 to 256K baud. To configure it to a certain baud your micro must send it the ASCII character “U” (56 hex) after a minimum of 500ms (allowing the uOLED to ‘boot’).

Problems arise if the serial lines are not stable when the display begins checking for “U”.
This was my problem – my serial lines were floating in the time before the microcontroller got controll of them, and the display was misinterpreting the garbage as a signal. I noted that a fellow who had wired a Telit GSM module to an ATmega8 had tied his serial lines high (connected them to the + power rail) with 10kohm resistors. I tried the same thing, cleaned up my messy “it’s not working and I’m getting frustrated” code and immediately had solid, reliable control over my OLED display.

Success! Now some tedious work to write various lower-level routines for the screen. My motivation for that will come – I’m just really glad I managed to get the comms working.

Special thanks, if you happen to read this one day, to Alexander at Tinkerlog!

Telit GE863

Telit have recently updated their website and it is a LOT easier to navigate now – well done!

Also they have a few more datasheets and application notes up, including one for battery charging, audio and antenna notes.

For the module I am planning to use, the info is available on their website.

It is based around the Telit module GE863 which supports quad band GSM, serial interfacing and even has a SiRFIII GPS chip inside. It will be hooked to the other primary component, an AVR ATmega microcontroller.

Coupled to the GE863 will be the original StarTAC’s microphone and earpiece, a GSM antenna and sim card holder. Coupled to the AVR will be the original keypad and a 4D Systems 1.7″ OLED display.

Power will be provided by an aftermarket StarTAC Li-Ion 3.6v battery and either an original StarTAC charger or a modified one.

I’ve so far put up the basic project page for my retro-style mobile phone, the RetroTAC. I’ll do more work on that soon and blog about my progress on the project so far.

To come there’s my gruntily-named “MaxxMonitorr” telemetry system for my Traxxas E-Maxx RC truck, as well as my digital timer photo capture circuit to link to my digital SLR camera. It has possibly been named the “Capture XTi”. Better ideas are welcome!

Here we go! DIY Gadgets!

I made this movie with my brother and our friends in 2002. It is plot-thin, and was primarily made for fun, and to test my skills at video editing and post-production special effects. I cringe at several things when I watch it, but I think overall it’s a good effort.

17Mb, 8min 40sec, Credits feature outtakes so watch to the end!