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Old 18th March 2009, 03:51 PM   #51
ramchip is offline ramchip  United Kingdom
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Default MAB8441 firmware

Hello MADSYSTEMES, yes I have made progress since my last post. The CD160 has been cracked, i.e. analysed to the extent that I understand how the track number is sent to the CDM in that model of Philips player. Note that the CD160 mechanism is of the sliding tray type. This was achieved using a PIC 16F877A and my home-brew bit-bashing technique.

I tried using similar code on the target system which has the MAB chip but a different style of CDM, it has a lid that is raised by a motor. This one has not been cracked as yet. The expected codes do not appear to be
present, indicating that the MAB firmware is different.

On my scope the I2C bus structure used by MAB is different to modern standards so I would be surprised if a current analyser gives meaningful results on the old kit.

However, if you find the track info for the MAB Im working with please let me know!

In the meantime, good luck with your project.

Regards, ramchip
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Old 18th March 2009, 05:55 PM   #52
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First of all, i'am very happy to see that you've got somegood competence.
If you want i can tell you what i know about the cdm4 products.
I am the boss of the service center in Paris,Bang &Olufsen have used a lot of cdm4 and i have a very good experience in all the models.I can tell you that the protocol used to work with pcb decoder are the same.I mean that they have the same basis.
I've capture some i2c datas with analyser that memorise it on computer.So i can capture for hours of play back.
After that i have all for doing prototypes and for work with 16f876a, emulator etc..
But tell me what do you want to do with this protocol?
What are the application?
perhaps it's better to talk in Private message.
Regards Carlo
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Old 4th May 2009, 06:22 PM   #53
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I will build transport based on Philips CD584 (CDM4/19, SAA7210, SAA7220, TDA1541A). Transformer (new toroid) will go in separate box, and vfd display will be replaced by blue 7-segment or matrix led. Also, any Sony/Philips remote will be used to control the device.

Original keyboard/vfd/IR front board will be replaced with my own. uC will be used for new display/IR control and I2C communication with CD uC (MC68HC05C8).

So, right now, on the original I2C bus are only 2 devices, MC68HC05C8 (uC) and TMS3763 (VFD driver). uC send to driver 2 times 6 bytes (display segment info), and after this read 3 bytes (keyboard matrix).

[01110000(1)00100010(1)00000110(1)00100010(1)011111 11(1)11110111(1)]
[01110000(1)00101010(1)00100000(1)01001100(1)001011 10(1)10110111(1)]
[01110001(1)10000001(1)00000000(1)]

In the first byte, there is DeviceID=7 (4 bits) Adress=0 (3-bits) and last bit is R/W. After this is ack bit, and other bytes with info. If someone have datasheet for vfd driver TMS3763, everything will be clear. If not, checking bit by bit, reverse engineering...
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Old 4th May 2009, 09:45 PM   #54
guido is offline guido  Netherlands
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From what i can remember when looking at a similar device in a CD80: 4-bit and programmable.

So you need a pre-programmed part to replace one. I'm afraid the datasheet won't help, as it does not explain the program inside.
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Old 5th May 2009, 10:56 PM   #55
guido is offline guido  Netherlands
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Found the datasheet of the part in the cd80; a different beast.
Also see that there's a 3763 in a cd650 schematic with the internal block diagram. No rom, so the datasheet should be enough. But can't help there.
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Old 10th May 2009, 01:22 PM   #56
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All vfd drivers in older philips CD players (in this case tms3763/u3090mg) are uC. Block diagram of tms3763 from CD852 service manual confuse me, but it is uC for sure (Vpp pin).

Reverse engineering process is finished. PC was used as I2C master (over LPT), for sending data to cd player front board, turning on/off each segment, and decoding keyboard. I was rigth in last post regarding the MC68HC05C8/TMS3763 communication. Last 4 bytes in two write commands are for on/off display segment (58 bits, 6 bits unused). Last 2 bytes in read command are presed key values.
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Old 22nd May 2009, 08:42 AM   #57
koko is offline koko  Hong Kong
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hi josiphal:
I have done test u3090s display code and your results different .my results Consistent the Block diagram of tfk-u3090mg from CD50 service manual.
can u send the reverse engineeing program and schematic circuit to me? thank you so much!


Regards,
koko
email:cuteykoko@hotmail.com
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Old 23rd May 2009, 08:20 PM   #58
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For reverse engineeing process is used PC with parallel port and simple program for collecting samples and start/stop recognition. I2C signal frequency was about 40kHz, so parallel port speed wasn't problem.

First, only monitoring communication between MC68HC05C8 (uC) and TMS3763 (VFD driver), with I2C lines connected to parallel port input pins...

[01110000(1)00100010(1)00000110(1)00100010(1)011111 11(1)11110111(1)]
[01110000(1)00101010(1)00100000(1)01001100(1)001011 10(1)10110111(1)]
[01110001(1)10000001(1)00000000(1)]

And after this, replacing MC68HC05C8 with PC, to recognize I2C message bits and VFD segments relation, with I2C lines connected to parallel port output pins by oc.

For me TMS3763 (VFD driver) is not important (is it uC or not), because it will be replaced with new display. For me is only important I2C data transfer, and now I know for what is used every bit in message.

This is the case for CD852, and if the story with other models is similar, or something completely different I don't know.
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Old 24th May 2009, 03:23 PM   #59
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I forget the schematic. The I2C/LPT interface is described in AN3230 from Maxim.
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Old 4th September 2010, 07:19 AM   #60
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hi
does anybody have some news for this IC protocol??
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