The author of this Howto will not be responsible for any problems or damage caused by the instructions below! If you decide to modify your DVB card, you should know what you are doing, and you are doing it on your own risk!
On full-featured DVB cards all data transfers go through a 8 KByte dual-ported RAM (DPRAM).
The DPRAM is a bottleneck, and limits the performance of the card.
A few years ago Roberto Deza had a great idea and developed the so called budget-patch:
Unfortunately, this approach has some disadvantages:
The solution below avoids these problems. It is called the
Warning: Try this only if you are experienced enough and have the equipment for SMD soldering!
Use the following pictures to locate the required signals on the pcb (marked with red arrows).
Note: For convenience all signals have been assigned the name of the corresponding saa7146 pin.
Obviously there are all signals available except for VS_B.
VS_B can be created using the following circuit:
For the prototype the chips were simply glued to the pcb upside-down and wired accordingly,
but you might also create a small pcb for this circuit.
Now connect the signals:
|D1_B0||av7110||saa7146 pin 145|
|D1_B1||av7110||saa7146 pin 146|
|D1_B2||av7110||saa7146 pin 147|
|D1_B3||av7110||saa7146 pin 148|
|D1_B4||av7110||saa7146 pin 151|
|D1_B5||av7110||saa7146 pin 152|
|D1_B6||av7110||saa7146 pin 153|
|D1_B7||av7110||saa7146 pin 154|
|LLC_B||av7110||saa7146 pin 157|
|VS_B||74HC74 pin 5||saa7146 pin 158|
|HS_B||av7110||saa7146 pin 159, 74HC4040 pin 10, 74HC74 pin 3|
|PXQ_B||av7110||saa7146 pin 160|
(See schematic for connections between 74HC4040 and 74HC74. Do not forget GND and 3V3!)
Please double check that all wires are connected properly and you did not produce any shortcuts.
The picture below shows the prototype (rev 1.3):
A better looking one (rev 1.5):
First test the card with the standard driver. The card should work as before.
If not: Turn off the machine and find out what's wrong!
Then install the latest v4l-dvb HG driver (or Linux Kernel >= 2.6.28) and load the driver with option 'full_ts=1'.
Everything should work as before, except that the bandwidth limitations are gone!
If you would like to avoid the parameter 'full_ts=1', you may use the script
to write the 'full-ts signature' to the eeprom.
Please make sure that you specify the i2c bus of the modded card! Do not use this tool unless you know what you are doing!
(The tool unpatch_eeprom may be used to remove the signature.)
Have a lot of fun!
Note that the modification might work for other board revisions, too. Please report success or failure.
For DVB-S rev 2.2/2.3 cards port B of the saa7146 is already connected to the av7110.
Basically you just have to solder two chips onto the board:
Special thanks go to Roberto Deza for inventing the budget-patch.Last modified: Wed Aug 12 02:25:48 CEST 2009 by Oliver Endriss