PMOD Digital Video Interface - Unsoldered Ports

1

Hi,

  I was reading about the PMOD Digital Video Interface board that 1 Bit Squared is selling and the fact that there are unsoldered ports on the board is a source of concern.

   Can you tell me why 1 Bit Squared, in design, chose not to solder some ports?

   Also, can you tell me exactly what port lines are not soldered (I did not see a schematic for this board - maybe you can point me to a link)?.

   Thank you.
2

Hi @Zynq_Guy,

Welcome to the forum.

You can find the schematics and even the KiCad design files of the Pmods on GitHub. Depending on which DVI Pmod you are referring to there are several different schematics. The folders are dvi-3bit, dvi-4bit, dvi-12bit, dvi-24bit.

I am not sure what you mean with “ports”. I guess you mean that some of the encoder chip pins are not connected? All pins that are needed for operation are connected or strapped to one of the rails or connected through a pull-up/-down resistor. There is no need for “concern”. :wink:

The Pmod interface has a limited amount of pins so we have to compromise a bit. And depending on the mode of operation of the encoder chip use a specific wiring scheme. This is why there are so many versions of the boards, it is not possible to make a fully universal board that can support all the modes the encoder chip supports.

If you look in the encoder chip datasheet. You can find that there are different modes. In case of the 4bpp mode we use a RGB input mode where we tie several bits of the data to one pin. This way we get a CGA style color palette. For the 12bpp board we still use the RGB mode but connect more pins to separate IO pins and use two Pmod connectors instead of one. For the 24bit board the wiring is again different as the encoder chip is reading two sets of 12bits, one on the rising and the other on the falling edge of the data clock.

It is all described in the encoder chip datasheet. You can compare it to the schematics of each of the Pmods. You can find Verilog examples for each of the Pmods in our iCEBreaker Verilog example repository.

I hope this helps.

Cheers,
Piotr