I'm currently playing with a Nokia style graphic LCD, which is a 3.3V 84x48 monochrome display.
As I was initially using it with a 5V 16F1827, I mounted the display on a board with a 3.3V regulator, and fitted 10K series resistors in the connections, for 5V feeds as suggested in various places on the net. I've got this working perfectly, and am very happy with it.
Next I connected the board to a 3.3V 24F board, and I couldn't get it to work?.
Sticking the scope on the data and clock pins the SPI signals on the 5510 were very small (about 1V p-p), and triangular rather than square, but it was fine on the input side of the 10K resistors. So I simply shorted out the two 10K's on CLK and SDI, and it works perfectly now.
I'm just wondering if anyone has any idea why the 10K's caused so much trouble with 3.3V signals?
As I was initially using it with a 5V 16F1827, I mounted the display on a board with a 3.3V regulator, and fitted 10K series resistors in the connections, for 5V feeds as suggested in various places on the net. I've got this working perfectly, and am very happy with it.
Next I connected the board to a 3.3V 24F board, and I couldn't get it to work?.
Sticking the scope on the data and clock pins the SPI signals on the 5510 were very small (about 1V p-p), and triangular rather than square, but it was fine on the input side of the 10K resistors. So I simply shorted out the two 10K's on CLK and SDI, and it works perfectly now.
I'm just wondering if anyone has any idea why the 10K's caused so much trouble with 3.3V signals?