Digital Display Information

[Firewatcher]

Hello All,
I am moving to the dizzy heights of a 1990s Blaupunkt Car 300 Radio Cassette, but my command of 'In Car Entertainment' technology is stuck in the 1970s. as is my Motor and worn out Radio Cassette. I still have and can record anything on cassette tapes and this deck hasn't done much work.
The Unit does not have an integral display, but does have output pins marked: SDA-1 BUS Display, SCL-1 Bus Display and MRQ-1 Bus Display. I have searched as far as I can online to find a simple way of displaying the output, but no joy, so looking for some advice here.
I am fine with the other wiring, and if pushed can do without the display, but it is useful when decoding, rather than counting the key presses and hoping the input is what I think it should be.
I am old fashioned all round, so anything that involves a mobile phone is out. I was thinking more on the lines of getting an LCDisplay Unit from a car of the same period and installing that if possible. Any ideas or advice would be greatly appreciated as I don't know anything about data outputs of this nature, or how they are translated into a display.
Pete

 

[augustinetez]

Well, first thing is - is it unlocked or do you have the code to unlock it.

Secondly, with out a screen it is unlikely you will get far as to making it operational.

Not knowing which country you are in, but in the UK, the separate screen display from a Vauxhall Opel should plug straight in from comments by various sellers of these things.

 

[Firewatcher]

Thanks for the reply. augustinetez, Yes I am in the UK and unfortunately, I don't yet have the code so it is still locked, but I have powered it up and managed to get the beep for code entry. It seems the code is a function of the Serial Number and should be obtainable for a small charge. The unit looks very clean inside & the cassette deck looks to be little used, so probably worth trying to get the code.
The information about the Opel Display connectivity is great news, and sounds like it will resolve the display issue. Thank you - exactly the kind of advice I was after. Pete

 

[augustinetez]

There's a few other vehicles, all various models of Vauxhall that have the same display apparently - let us know how you get on.

 

[Firewatcher]

Hi, Yes, I will take the unit with me to the scrap yard later and see if I can find something - will keep progress posted.
Thanks again, Pete

 

[Firewatcher]

Well I did promise to keep progress posted and in fairness that includes my mistakes. Found a Corsa with Display and Radio plugs intact - and it looked like the business. Unit fitted snugly into the factory fitted bay and so I spent a couple of hours removing the display and section of harness that linked with the plugs.
Only once it was out could I see that the connectors on the data plug are transverse. It must have been fitted with a Siemens Audio Unit - Plugs look close, but significant difference in pinouts so my mistake but I did think it had fully engaged .
Luckily I am retired, so can spend a disproportionate amount of time on things that don't seem worth it to anyone else. I will have another go directly.
Pete

 

[augustinetez]

This link gives the other models with the display and also shows the display.
https://picclick.co.uk/Vauxhall-Blaupunkt-Car-300-Car-Radio-Cassette-Player-275160471197.html

 

[Firewatcher]

Thanks for the link, I will make certain before removing the next one.
Interestingly it looks like the same Guy is also advertising a Seimens CD/Radio and has the same display connected in both adverts. I did notice the signal outputs from the Seimens unit also has SDA, SCL and MRQ Display Outputs so, it looks like they both work on the same protocol. The Seimens Display I took out has the control buttons on the RHS rather than the left as in his ads. But it is beyond my technical ability, and I can't find any pinout details for either of the display units. So back to plan A - Find a display complete with the correct plugs.

 

[Pommie]

FYI, the SDA and SCL lines are the normal communication lines for I²C (IIC or I squared C - Inter Integrated Circuit). It's a standard protocol.

Mike.

 

[Firewatcher]

Hi Mike, Thanks for the clarification, as you can see my command of electronics is let us say, non existent. But since my earlier post, I have now found some reference as to where to connect these outputs to the display and might experiment out of interest. I have nothing to lose and might actually learn something about how this type of display is driven.

 

[Pommie]

My guess would be that the minimum number of connections is power (2) and the I²C (2) lines, making four in total. You mention a MRQ line, not sure what that could be. Memory ReQuest maybe. It's possible the front panel contains a memory chip to hold the security number.

If you have a panel that won't fit then you could hook it up to an Arduino and have a play with it. There are (readily available) I²C scanners that will tell you the address available and then you could connect to the radio and mimic that address to see what gets sent to the display. This could be repeated until a full conversation has been revealed and then try to work out what it all means.

Assuming you know how the panel connects then you may be able to use an I²C recorder between the devices to get a full conversation.

Good luck whatever you decide to do.

Mike.

 

[Nigel Goodwin]

Hi Mike, Thanks for the clarification, as you can see my command of electronics is let us say, non existent. But since my earlier post, I have now found some reference as to where to connect these outputs to the display and might experiment out of interest. I have nothing to lose and might actually learn something about how this type of display is driven.

While I2C is a standard protocol, that doesn't mean that in any respects can you hope to simply swap units unless they are EXACTLY the same hardware and software.

I2C is a bus to connect between IC's on a PCB board using a simple two wire connection. Each IC has an address, which can usually be assigned a number of different ones, and many ICs require lot's of setup data transferring over the bus to make them work. Even if the IC's are all the same, it only needs one to be configured to a different address, and nothing will work.

The fact that the sockets are different genders lends me to think that they probably aren't compatible?.

 

[Firewatcher]

Again, I am a complete novice here, but it looks like very basic SCL Master - Slave arrangement where the communication only needs Serial Clock Line, Master Request, and Serial Data - 3 wires (excluding any power requirement) The slave is a display only so there is no need for it to send anything back to the master.
If correct that lines up with the SCL, SDA & MRQ output pins for the display.
I will put some power on to it and have a play later, it looks like the time clock is integral in this one, so I should see somethng. It is a 12pin connector marked GM ZF12-9, can't find a pinout for it but can get an idea from the wiring colours and pinout from the radio.

 

[Nigel Goodwin]

Again, I am a complete novice here, but it looks like very basic SCL Master - Slave arrangement where the communication only needs Serial Clock Line, Master Request, and Serial Data - 3 wires (excluding any power requirement) The slave is a display only so there is no need for it to send anything back to the master.

Doesn't the display have buttons on it?, which presumably are sent back to the radio?. Both I2C and SPI are bi-directional, so data can go both ways.

If correct that lines up with the SCL, SDA & MRQ output pins for the display.
I will put some power on to it and have a play later, it looks like the time clock is integral in this one, so I should see something. It is a 12pin connector marked GM ZF12-9, can't find a pinout for it but can get an idea from the wiring colours and pinout from the radio.

It depends a lot if it's I2C or SPI, which are fairly different - and again, it relies on both items being electronically identical, and using similar software.

 

[Firewatcher]

Hi Nigel,
The display only has buttons which I think set the time clock display, I took it that this a one way communication from radio to display and although SPI can work bidirectional, in this case it doesn't need to, so the Slave to Master signal isn't necessary.
As I say I will put some power on it later and post what happens.

 

[Nigel Goodwin]

Hi Nigel,
The display only has buttons which I think set the time clock display, I took it that this a one way communication from radio to display and although SPI can work bidirectional, in this case it doesn't need to, so the Slave to Master signal isn't necessary.
As I say I will put some power on it later and post what happens.

I would suggest it's probably more likely to be I2C than SPI, as it's a much more popular connection, with vast numbers of chips available.

Is the clock display free running, even with the radio unplugged?.

 

[Firewatcher]

Hello Nigel,
The plot thickens, I have now connected the display directly to a 12V car battery using three of the 12 terminals. Constant live, Switched live and Ground. I get a date and time display and can set both using the two buttons on the unit. That is what I hoped would happen and seems logical from what little I have found so far.
I havent connected the data pins yet but will set up the radio and try this evening.

 

[Nigel Goodwin]

That's good news so far anyway

 

[Firewatcher]

Can't really identify the radio pin positions on the display connecting plug. It's a multifunction display with 12 pins and I am only sure about the few where the colours correspond to information I have found. Of the others, I can only eliminate a few with any degree of certainty so the chances of guessing the right configuration are poor.
Back to plan A, and put this on the back burner.

 

[Firewatcher]

Grabbed another Display from an Astra this afternoon, with the correct radio plugs for the unit I have. At the same time I picked up an external tempertaure sensor - also one of the functiions of this display - I think the correct term is TID (Triple Information Display)
Fortunately the wire colour coding was much nearer the information I have, so very successful and I now have a working TID on the dining table.
In terms of the communication between the two - it does only use the three wires. That is - a one way communication from radio to TID. There is quite a bit of additional logic within the display itself, for example it needs to see Power On to the radio to clear the date display and replace it with the radio status/information.
The outside sensor is a simple two wire connection & supplies a variable resistance.
Just have to get a code to unlock it now - 7 attempts left.
I would like to thank you all for the help and interest shown on this very successful little job.
Pete