Support to non consecutive VGA_GPIO_SYNC

[dquadros]

I am using PicoVGA with a RP2014 Zero board that has a more limited option of pins than the Pi Pico. I want to use UART and SPI and for that I need to assign VGA_GPIO_SYNC to a GPIO that is not consecutive to the color pins. From a quick look at the code, it seems that this will only affect the pins initialization in vga.c, (VGA_GPIO_SYNC would need to be initialized separately):

// connect PIO to the pad
for (i = VGA_GPIO_FIRST; i <= VGA_GPIO_LAST; i++) pio_gpio_init(VGA_PIO, i);

...

// set pin direction to output
pio_sm_set_consecutive_pindirs(VGA_PIO, VGA_SM(layer), VGA_GPIO_FIRST, VGA_GPIO_NUM, true);

Can you confirm this? Is this change worth a pull request?

[Panda381]

Yes you are right. It was my mistake not to take into account that synchronisation can be separate from colour. Yes, it is sufficient to initialize SYNC separately. I want to point out a second problem yet - some monitors (rarely, rather older types) do not support CSYNC composite sync. If the output doesn't work for you, try it again on another monitor, preferably a newer LCD.