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PostPosted: Fri Aug 28, 2009 22:56 

Joined: Fri Aug 28, 2009 21:22
Posts: 2
OK guys, im just wondering if anyone can help me on this...

my car [1993 vauxhall [also known as opel / GM] astra has a lcd screen...

in the screen is three sections = one lcd screen with 51 pins on... would anyone know how to...
1) use the WHOLE display
2) use the central section that displays just the date / stock stereo data.

4 wires go to my stock stereo... but i cant find any markings on the board or anything to suggest how to make it work...

- i wanna be able to use this connected to my car puter = so as to keep a Manufacturers finish to my car = dont want it to be broken into for my cheap computer that i have put lots of work into making work.


thats my screen on the dash...

the 1st n 3rd sections are controlled by a onboard cotrol chip that like i said my 4 stereo (and one stereo remote [power on]) cable connets to... i just dont understand HOW to use this... - im happy with whatever i can get, just the fact the screen itself [even though there is onl 12 pins go into the unit] has 51 connections... HOW???

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PostPosted: Fri Oct 23, 2009 22:08 

Joined: Fri Aug 28, 2009 21:22
Posts: 2
ok info: PC in my car = replacement media centre.

i want to connect the original info display to my pc, to display track names etc [tracks r played via my application]

ive found info on the display here:

unfortunately im not of the "intelligence" to understand how this works but have an idea...

Connect pin 1 - 3 LPT to the SDC SDL MRQ

use the outputinput Dll to alter the on/off state of pins on the lpt port...

but heres the problem... - I dont understand HOW i send the info etc?

maybe somebody can help me with this?

info from link:
Looks like a mess. But it can easily be explained. First click the picture to enlarge. In this picture each pixel in the X-direction is a sample of the three communication lines used. The black line is SCL, the blue is MRQ and the red is SDA. There are 65535 samples taken in 2.00 seconds. The sample rate is 32.8 kHz. The time each sample presents is about: 30 microseconds.

The radio was turned off. The measurement was set to start on a change. Than the radio was turned on. The result:

   1. The power up sequence of the car radio shows that all three go low followed by a low pulse (line test?) of each line. Pulling MRQ is acknowledged by the display by pulling SDA low. Next there is a long period that MRQ is low This is a sort of reset pulse coming from the radio. The display responds by pulling all three lines low.
   2. After an idle period (all high), you see a communication block. It is started by MRQ going low for a short period. Than an I2C start is send (SDA goes low while SCL is high). Next the address byte is send according the i2c protocol. Next MRQ goes low. And than the 10 data bytes follow. Next MRQ goes high and a I2C stop is send (SDA goes high while SCL is high).
   3. And a second communication block is send, but the data makes no sense, as it suddenly appears to be terminated.

Analyzing the protocol shows:

   1. Idle state all lines are high.
   2. Pull MRQ low for a short period and let it go high again.
   3. Send a "I2C Start"
   4. Send the address byte (0x94).
   5. Pull MRQ low.
   6. Send 10 data bytes
   7. Let MRQ go high
   8. Send "I2C Stop"
   9. We are back in the idle state.

The bytes contain in total 9 bits. First there are 7 bits of data followed by a parity bit (odd-parity) followed by an acknowledge bit (Part of I2C specification). The first byte is the address byte of the display. The next two bytes control the "lights" like "CD", "RDS" and the decimal points. The following 8 data bytes contain the characters to be shown on the display using 7 bits ASCII. Decoding the first block results in:

   1. 0x94 = 10010100A (This is the I2C address of the display)
   2. 0x10 = 00010000A (Turn one light on, I did not bother to check which bit belongs to which light.)
   3. 0x01 = 00000001A (Turn the other lights off)
   4. 0x8C = 10001100A = "F"
   5. 0xA4 = 10100100A = "R"
   6. 0x8A = 10001010A = "E"
   7. 0x8A = 10001010A = "E"
   8. 0xB5 = 10110101A = "Z"
   9. 0x40 = 01000000A = " "
  10. 0x8C = 10001100A = "F"
  11. 0x9B = 10011011A = "M"

The Display has a 12 pin connector which is described as follows:
Pin #    Name    Description
1    Permanent 12V    Always on 12V, keeps the clock running.
2    Not connected (Temperature)    Temperature for TID
3    Ground 0V    Ground connected to the chassis
4    Not connected (Temperature)    Temperature for TID
5    Accessories    12V when the key is on accessories. The display goes on.
6    Headlights    12V when headlights are on.
7    Dashboard illumination     Signal for the strength of the dashboard lights
8    Car-radio on    The Radio is on. The date will disappear and make space for the RDS signal
9    SCL    Serial Clock
10    MRQ    Master Request or something...
11    SDA    Serial data from the radio
12    Not connected (Speed)    Speed signal for displays with temperature readout. (TID)

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