Guru
Joined: 31/12/2012
Location: New ZealandPosts: 2502
| Posted: 02:30pm 24 Aug 2024 |
i think what Peter is wanting to say is that, if the HDMI output is being used on an RP2350, then GP12-GP19 and unavailable as these 8 pins are used for the video drive signals. that is 4 pairs, one for each of the R, G, B, and clock channels. when video output is being used, these pins are hardwired for the task.
when using the RP2040, the pins reserved for VGA signals are GP16-GP21, being 4 video signals (R, G1, G2, and B), plus Hsync and Vsync. when video output is being used, these 6 pins are similarly hardwired for the task.
i am guessing that VGA output from an RP2350 is also hardwired to GP16 - GP21.
by "hardwired" i mean either the onboard hardware of the processor chip can only use this specific set of pins for task (as is the case with HDMI on the RP2350), or are hardcoded to the specific pins in the MMbasic firmware (i'm pretty sure this is this the case with VGA on RP2040 and RP2350, i can not find any OPTION VGA... setting in the manual i have here).
in all the above cases, if you use a MMbasic firmware that does not make use of video output, then the pins (GP12-GP19 or GP16-GP21) are free to be used for whatever else you wish.
with an SD card is attached, any group of four otherwise unused GPIO pins can be used for the task, as the SD card's communication is entirely bitbanged by the MMbasic firmware.
Peter, have i got this right?
cheers,
rob :-)
Edited 2024-08-25 00:51 by robert.rozee