Has anyone used the P2 outputting LVDS to drive an LCD?

Cluso99

I’ve been looking to connect an old laptop screen to the P2. I ordered a VGA/DVI/HDMI to LVDS LCD controller pcb to do this.

However, looking a little more into this I can drive the LCD directly with LVDS. I can do this by using a Serial to LVDS chip such as the DS90C363 and output the 21 RGB+ lines and 65MHz clock from the P2.

So looking a little deeper, can the P2 output the LVDS directly? There are 4 LVDS channels required, one of which is the 65MHz multiplied by 7. RGB is 6/6/6 bits.

rogloh

There has been some success with LVDS LCDs directly attached to the P2, yes. But 65MHz x 7 is too fast for the P2, requiring 455MHz operation to stream the bits out. You'd need to find a display that can be clocked with a slower dot clock, more something around 20-40MHz for example if you intend to attach directly, which may then need a slower vertical refresh depending on resolution. The parallel to LVDS is probably your best bet for high resolution displays. I still want/need to add a parallel output mode to my video driver at some point too. I know I already did some initial planning work in some other thread and think it should be doable. Mostly a sync related change and slightly different streamer settings.

Tubular

I suspect it will be possible using the streamer in 4 bit mode, and the smart pins in bit dac mode. However its probably worth getting up and running using the proper conversion IC first, as intermediate step.

There was a previous effort using a lvds display posted here, but it used the conversion IC

Cluso99

Just came back to post it’s not possible because 65*7 = 455MHz. I see you’ve already said this

The streamer should be able to help here but the clock will need to be output at double this speed 65*2 = 130MHz, but the data will need to stay the same for both high and low of the clock. Not sure if the streamer can do this?

n_ermosh

I made a small demo of it here: https://forums.parallax.com/discussion/171516/p2-fpd-link-lvds-displays

I never fully finished turning it into its own module, but the proof of concept is there. As mentioned above, you need a display that’s happy being clocked slowly. There’s some discussion on improvements that can be made, but I got distracted with another project before I could finish it (my llvm compiler)