D8-D15 seem to be floating

[rjonkman]

I'm sending an array of alternating 0x0000 and 0xFFFF integers using the SglBeatWR_nPrm_16() method.

uint16_t pix[400];
for (int i = 0; i < 400; i++) {
   if (i % 2 == 0) pix[i] = 0xffff; else pix[i] = 0x0000;
}

lcd.SglBeatWR_nPrm_16(0x02, pix, 8);  // I made the method public for testing

When probing pins D8-D15 with my scope, they always stay low or sometimes float just a bit above 0v. Pins D0-D7 work as expected. I have properly defined the bus width to 16. Have you tested this method using a 16 bit interface on a T4.1?

#define BUS_WIDTH 16 /*Available options are 8 or 16 */

I also confirmed that my display is not pulling the pins down, as I can put a pull up resistor on the pins and see them go high on my scope.

UPDATE: Here are a couple screenshots from my scope. In both images, channel 1 is on the WR line. In the first image, channel 2 is on one of the D0-D7 pins, and in the second it's on one of the D8-D15 pins.

[david-res]

I have this library running on a Teensy 4.1 & ILIL9488 in 16 bit mode. So it should work.

[rjonkman]

Well, it's definitely not working here. I even completely removed the display, bypassed LCD initialization, so I was just working with the SglBeatWR_nPrm_16 method, but I still can't get pins D8-D15 to work.

Small ask: Can you tell me what version of TeensyDuino you are using?
Big ask: Can you hook a scope up to your device on one of the D8-D15 pins to show that it's working?

[david-res]

ILI948x_t41_p/ILI948x_t41_p.cpp

Line 528 in c32394e

| FLEXIO_SHIFTCFG_PWIDTH(7); /* Bus width */

Try changing 7 to 15 and see if it works
I should have put BUS_WIDTH-1 in there

[rjonkman]

Yup, that fixes it. I changed it to :
FLEXIO_SHIFTCFG_PWIDTH(BUS_WIDTH-1);

Thanks.. Getting closer now.