Teensy 4 and Riverdi 70H not working

[julianfawkes]

Hello, I've had good luck with the GDSTx library on my setup here but wanted to switch to yours to eek out some more performance. However, the built-in example in this project doesn't work at all - the backlight powers up but nothing else happens. Any idea what's happening here? One thing that might be important to note is that my PDN pin is not connected, and the whole thing is already integrated in a PCB so I can't add it. This hasn't been a problem in the other library.

Any ideas as to what might be wrong would be much appreciated!

[RudolphRiedel]

Hi,

check EVE_init(), if you add EVE_SOFT_RESET to your build environment you can get away with not wiring the PD line properly.
I am thinking about removing the condition, but there are hardly any display modules with no PD line.

[RudolphRiedel]

Oh yes, did not spot this:
EVE_cmd_dl_burst(DL_VERTEX2F | 0 | 250);
EVE_cmd_dl_burst(DL_VERTEX2F | 250 | 0);

This does a line from 0/250 to 0/250. :-)

[julianfawkes]

One last question if you don't mind :-) It would be great if you could help me with appends.

I have a collection of many points, and I want to display them all on a single frame. It's a real-time plot for audio data. I'm sending the points in a burst, however the total length of this burst is longer than the limit of the fifo. What I would like to do is space out a series of bursts that all write to the same frame. E.g. send a burst of 200 points, then append another 200 points to that same frame, then append another 200 points, etc. If I'm understanding the display list correctly, all of these bursts would be going to one display list, right?

The cmd_append_burst() command takes a pointer and a number, and I'm not sure how to use these in my case. Could you give me a quick list of the commands I would have to use to get this working? Thank you in advance again!

[RudolphRiedel]

Yes, the cmd FIFO is limited to 4kiB.
But then the display list is limited to 8kiB and the co-processor commands usually generate several display list commands.
It is less likely with a lot of points, but if you reach the limit of the cmd FIFO you usually have reached the limit of the display list as well.

So yes, using command-append can work, you generate a display-list, do not use DL_DISPLAY and CMD_SWAP in the end, read back REG_CMD_DL and use CMD_MEMCPY to copy the display list segment to some place in RAM_G.
Check out my initStaticBackground() function in tft.c of the examples.
I am not using DMA in this function but it only is supposed to be called once.

So you could do this to generate segments and then use CMD_APPEND to copy these all together to form the final display list.

However, you can skip the part with the command append.
Start the first segment with EVE_start_cmd_burst() and CMD_DLSTART as usual, stop the segment with EVE_end_cmd_burst().
Then after the transfer is finished, just EVE_start_cmd_burst() / commands / EVE_end_cmd_burst().
And the last segment ends with commands DL_DISPLAY and CMD_SWAP.
As you need at the very least 16.67ms between two display updates anyways, you could for example write a short segment ms with the final segment to trigger the swap after 20ms.

[julianfawkes]

I think I get it! I made a loop with the series of start burst and end bursts on a single display list, and I max-out at around 220 points on the screen. Anything more and I get crazy tearing and artifacting. Is this normal? This limit is consistent whether I use bursts or not. When using the Gameduino library, I can go up to >700 points.

[RudolphRiedel]

If you can go higher using the Gameduino library, then this is not normal as the same limitations apply.
What size is your display list at 200 points?
Please post some code, it does not need to be complete or compile, just to have a look at what exactly you are trying to do.