dc_port of dm642

david pian said:

my question is how to control the dc_port's pins  of dm642 when sending data.(Note: these pins are connected to the video port(vp1,2,3 ) of dm642).

I assume you are using the Spectrum Digital EVMDM642 board.  If so, there is good information on Spectrum Digital's support site for that product.

The Video Port Daughter Card Connections are detailed on page 14 of the EVMDM642 schematics.  You will notice the signals from/to these connectors, DC_P1 and DC_P2, also go to some CBT switches to enable use of the on-board circuitry as well as the Daughter Card Connections.  In order for you to use the Daughter Card Connections instead, you need to turn off the CBT switches, which will disconnect the Video Port signals from the on-board circuitry.  This is done by controlling EXP_DISPLAY_EN#, EXP_CAPTURE1_EN# and EXP_CAPTURE2_EN# from DC_P1 and DC_P2.

I would also suggest looking at the EVMDM642 Technical Reference Rev. A in Section 2.6 which discusses the use of the Daughter Card Connectors.  Here it indicates that EXP_DISPLAY_EN#, EXP_CAPTURE1_EN# and EXP_CAPTURE2_EN# must be driven to a logic-1 to enable the use of the Daughter Card Connectors.  We can see from the schematics that these signals are pulled low via pulldown resistors on the EVMDM642 to enable the on-board circuitry by default.

david pian said:

My question is, is that these signals may come from the daughter card xevm642.

Though I have never used the xevm642 board myself, I see no reason that the xevm642 could not interface with the video ports on the DM642 EVM connectors, as it would likely need to if you were using the xevm642 daughtercard for any video processing since you would need the bandwidth. Perhaps I do not entirely understand your question?

Hello David,

I dont have the EVM642 but the EVM648 - the similar evaluation board for the DM648.

On my board the VideoPorts from the daughtercard-sockets are multiplexed with an analog video decoder. In my case I have to switch this multiplexer to the correct input (DC) before the videoports are connected to the DC. On the EVM648 there is a microcontroller (MSP430) that is connected to the DM648s I2C bus. The multiplexer can be switched through I2C writes to this MSP430...

Maybe it is somehow similar in your case and you just need to 'switch on' the DC-Videoports.

It would be interesting to know what the reason was - maybe you can post it here ;-) best regards,

Thomas