There are lots of interesting displays hiding in cell phones, cameras, mp3 players and various other devices. In this post we will be looking at two of my non-Nokia favorites: The iPod Nano 2G display and the so called “cheapest TFT in the world”. Then we will be making a gadget that hopefully does something useful with them. To repurpose a display we need to determine its interface mode (serial/parallel), pinout and driver ic. If the display has a nice part number printed on the side then you might get lucky and have the interwebs answer all your questions. Much more often than not you have to do it the hard way. Count the number of pins on the connector. If there are 8-16 pins it is almost certainly a 8 or 9 bit spi interface. Find the LED supply pins (almost always the thickest traces on the flex) and give them the respect their elevated voltages deserve. Attach a logic analyzer to a live system determine the spi clk (wiggles most), the spi mosi (wiggles second most), the spi select and the reset (wiggles once). See this example. If you have 20 or more pins you have an 8 bit parallel interface. If you have 24 or more chances are it is 16 bit parallel. Many displays have the ability to run in both serial and parallel modes that can be selected with one or more external pins. If you are short of GPIOs this is a good option.
The iPod Nano 2G has a lovely little 22 pin transflective 176×132 screen. It has a 0.3mm pitch connector as seen in the iFixit tear-down. Nearly all 0.3mm ffc connectors have an odd number of pins. Apple thought different and used a DDK FF12 that is very hard to come by. After buying lots of replacement LCDs ($5 ebay + many $1 auction wins) and lots of dead/dying nano2Gs it was time bust out the fine transformer winding wire and a logic analyzer.
The data bus is easy to find: look for 8 consecutive bits that change all at the same time. The WR, CS and CD signals are then fairly easy to spot based on decreasing activity. As it turns out there are at least two different driver ics in these screens: A narrow one that looks a lot like a ILI9163 (8 bit wide commands, sets up blits with 0x2C) and wide one that looks a lot like an ILI9320 (16 bit commands, sets up blits with 0x22).
Although these controllers are similar to documented controllers they still have major differences and I needed to record an initialization sequence from a live boot in order to get them to work.
Connector pinout Nano 2G 1 LED+ 6V 2 LED- 3 Frame Marker 4 GND 5 D7 6 D6 7 D5 8 D4 9 D3 10 D2 11 D1 12 D0 13 RD Read 14 WR Write 15 CD Command/Data 16 CS Chip Select 17 Reset 18 GND 19 VIO 3V3 20 VDD 3V0 21 ID0 22 ID1
If one dismembers enough mp3 players one starts to notice patterns of part usage. One display caught my eye: it was very common in cheap 128×160 mp3 players, was a crisp and high contrast TFT, and had a hot bar solder connector that looked like it could be soldered by humans.
After dismembering a very nice Insignia digital photo keyframe and applying the logic analyzer the traces look very familiar. It was a ILI9163. Other devices turned up a ILI9161 and a Samsung S6D0144. All variants seem to have a very similar physical outline; another defacto standard like the touchscreen used in microtouch.They are widely available in China for $2 making them the cheapest TFT going.
The smartlcd adds intelligence to a TFT 20 display. An inexpensive Arm Cortex M0 or M3 microcontroller is used to provide graphics and media processing as well as providing a high speed serial interface the 3v3 display. With additional components the smartlcd can offer a spi-flash or microSD file system and usb. One single pcb scales from bare bones serial through to a stand alone lipo battery powered device.
// Console demo int a; a = analogRead(A0); a = analogRead(A1); if (_mode == 0) Console.Write("X:%d Y:%dn",a,a); else Console.Graph(0,1023UL,a,2); // Circle demo int x = random(128); int y = random(160); int r = random(70); int c = random(0xFFFFL); Graphics.Circle(x,y,r,c,1);