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JTAG DRX 890-C (Read 15301 times)
Matt52656
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Re: JTAG DRX 890-C
Reply #15 - Jan 13th, 2017, 1:59pm
 
This is in response to the message on the other thread.....
 
Quote from delboy1234 on Jan 13th, 2017, 12:34am:
That's some impressive work. Did that give you full access to the board over an i2c connection? How did you go about tracing pintouts on the board for something like that.

The new HD boxes (DRX890) also use a similar MIPS32 processor in the form of BCM7335
I have got a pinout for the BCM7335 that shows EJTAG and BBS pinouts but as your already aware they don't seem to be active.
BCM7335_EJTAG.zip (attachment)

 
AAAHHHH you have a diagram which shows you some pin numbers, that should be really useful.  Did you find the pins on the board ???
I "guess" it would be best to hold the RESETb line down while you power up the board, so its more lightly that the ejtag would be accessable using something like UrJTAG (or whatever you use) ?.
 
IMHO I would give-up on the I2C/BBS connection because I think Sky would never allow this.
 
 
About finding the board pinouts (on a Thomson box not the Amstrad).....
All those connections were direct pins to the flash.  I see that sky uses dual flash's for backup so I removed one of them to see the pins.
* Unfortunately I removed the primary and not the backup, which caused power on issues.  So I had to bodge the CE lines *
The thing that helped me map out the pins was aluminum foil... I had one of the multimeter probes on a flash pin, then I rubbed the probe (with the foil) over the board until I heard the annoying buzz from the multimeter.
 
Another thing I did for completely different small BGA chip, was to cut a very thin strip of foil and slide it under the chip.  So I could find the outside pins 'quite' easily.  But the inner pins were a pain.
 
Heres some old pictures, because I'm guessing you are curious.
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delboy1234
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Re: JTAG DRX 890-C
Reply #16 - Jan 19th, 2017, 10:37pm
 
Unfortunately not. I connected the jtag to the board in what I thought was the correct area but didn't get anyting back from urjtag.
I could of messed up the pull up resistor values, got the wrong connection for the RESETb line or just damaged the board when soldering.
 
Picked up a new DRX890 today so hope to have another try over the weekend.
Either was its good to see some activity in this and the other thread again!
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johnjoes58
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Re: JTAG DRX 890-C
Reply #17 - Apr 28th, 2017, 10:06am
 
Quote from delboy1234 on Sep 29th, 2014, 2:42pm:
Unfortunately still not having look with JTAG/i2c. The msi file is the correct one for BBS so that isn't the problem. I managed to find somewhat of a chip diagram (_http://www.2shared.com/document/nkt6a6wF/BCM7335_EJTAG.html).
After looking at this it took me to somewhere else on the board for the i2c port but still the same result. When the cypress board is connected the box fails to boot properly but nothing past that.

I still think its possible to connect to the box but i'm wondering if the chip is somewhat 'password protected' What I mean by that is you would need to use a key sequence or command to connect. Again no luck with this either so far.

If anyone has any other ideas on this let me know what you think

 
Has anyone got a working link for the drx890 chip?
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