PinsToVGA

Hardware display pins, to VGA video via microcontroller

20 pins, 128x64 LCD Display

LCM12864C, as found in Elektron Monomachine

Initial investigation:

pin 1 at right, ground
(all others measured relative to pin 1)
2 3.84v
3 -4.48v
4 5.04v
5 NC
6 Noise during transitions
7-17 Noise / data channels (5v)
18 roughly -3v
19 5v
20 NC

Actual pinout:

1) Ground
2) Supply voltage 5V
3) Contrast adjustment
4 high) to display data
4 low) for instruction code
5 high) read from register
5 low) write to register
6 high) read data
6 falling) write data
7-14) 8-bit data
15) Active high, select IC1
16) Active high, select IC2
17) Active low, reset signal
18) Output voltage for LCD driving
19) Backlight 5V
29) Backlight ground

Memory Storage in C

128px wide = 16 bytes 64 lines = 64 rows

byte buffer[64][16] = {}

Scaled to 640x480

128x64 @ 5x

128 * 5 = 640 64 * 5 = 320

Vertical back porch lines 33 Vertical front porch lines 10 Vertical line count 525

33 + (525 - 33 - 10 - 320 / 2) 33 + 81 = 114 Start drawing at line 115 Stop drawing at 115 + 320 = 445

VGA Spec on Teensy 3.2

Teensy 3.2 @ 96 MHz

Vertical Sync (frames):

60 Hz 64µs low sync pulse Normal high

525 Total Lines 2 sync pulse lines 33 back porch lines 480 visible lines 10 front porch lines

Horizontal Sync (lines):

85 nops 3.8 µs (sync pulse)

39 nops 33 pixels 1.92 µs (back porch)

611 register writes or 603 nops 25.4µs (draw time)

10 nops 640ns (front porch)