DVB-SPI Interface

TTL level hookup


Updated April 4 2007

Interfacing to TTL logic MPEG-2 transport streams

The DTVWorks DVB-SPI interface receives LVDS (low voltage differential) signals from the connected equipment. If the device doesn't have LVDS but you can find the MPEG-2 transport stream at TTL levels (around 0v for 0 and 2.4v or higher for 1), you can modify the LVDS board and connect the two devices with a short ribbon cable - really short - as small as you can and no longer than 15 cm (about 6 inches).

There are 10 signals plus ground that need to be connected:

D0..D7 The eight data bits
CLOCK The MPEG-2 byte clock
VALID High when MPEG-2 TS packets are being sent, low for Reed-Solomon parity data.
GROUND  

Many parallel MPEG-2 interfaces have two additional signals - SYNC (indicates when a packet starts) and ERROR (indicates if thre was an uncorrectable error in the packet). TSReader is able to determine both of these signals in software - the MPEG-2 transport packet sync byte 0x47 is used in software as the SYNC signal and when an error occurs, most demodulators will set the TEI bit in the packet.

Bottom Layer Cut

First thing that needs to be done is to cut the 3.3v line going to the LVDS receiver chips. After the trace has been cut, be sure to use a continuity tester (like an Ohm meter) to verify the rails are disconnected.


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Top Layer Connections

The top layer connections should be made to the points shown on the picture below. Make sure you hook up to the side shown of the 56 ohm dampening resistors - you want these in the path of the MPEG-2 stream to reduce the ringing of these signals.


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Devices We've Connected To

Newtec DVB 2063 Satellite Demod with HSSI/G.703 output board. Nothing special hooking this device up.


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Motorola/General Instrument HDD-1000. There's no VALID signal on this interface, so tie the VALID line to 3.3v.


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Comtec SDM-2020

Documented by Dave Emery on this page.