I have strange behavior with the Satistronic RT2002A2 20x2 LCD: it keeps displaying a line of blocks on the upper lines. The cabling is one-to-one and I can measure 5V at pins 1&2 and a variable voltage (backlight contrast!) on pins 15/16. So this looks OK, right?
It is not in the LPC17 core nor the MIDIO128 software as my old and unpractical 16x2 LCD functions properly. I also double checked with a second RT2002A2, which also gives only a line of blocks.
I think I managed to track down the problem to the RW line: Without the display connected, measurements for RS, RW en E (when set to 1) are ca 3.3 and ca 0,2V when set to 0. D0-7 have ca 5V for 1 and 0V for 0.
But when I connect the display, the behavior of RW changes: it has always 5V! It is not a short at the pins soldered on the display (confirmed by multmeter beep test). Could the pull-up issue play a role (in other thread) or do you still suspect my soldering ;-) ? (btw. the other pins act normally with the display connected).
If it is the pullup problem, where should I make what changes to the code?
Thank you very very much. But alas, it does not help. The old 16x2 happily says Midio128 V3.014 but the new 20x2 only shows an upper line of blocks. Should I retest with testlcdpin?
with testlcdpin rw 1: 3V36 at j5a/b and p1.27on lpcxpresso without cable and display; and with cable only (no lcd); with testlcdpin rw 0; same spots and connections 0v24
with cable and LCD connected; however, the same measurements at j5b (cable is at j5a) and p1.27; but still always 4v96 (rw 0 and rw 1) on the lcd itself. But measuring between Vss on the LCD and j5b.rw // p1.27 both with rw 0 and rw 1 gives proper voltages ie. 3v36 and 0v24. It is either the cable or the LCD itself then, is that correct? There should be something with the cable, otherwise measurements at j5b.rw = p1.27= lcd.rw, right? But why only the RW line? that does not make sense to me. I’d expect an improperly connected cable to give more problems, not on one line.
Measuring resistance between Vd (+5V) and RW pins on the lcd gives about 830R with - on vd and + on rw. Other way around is about 750k.
Should I get more flatcable and try make another cable?
but still always 4v96 (rw 0 and rw 1) on the lcd itself. But measuring between Vss on the LCD and j5b.rw // p1.27 both with rw 0 and rw 1 gives proper voltages ie. 3v36 and 0v24.
shows, that there is no direct connection between the LCD RW pin, and the core RW pin (btw.: you mean J15B, not J5B)
Otherwise you would measure exactly the same voltage.
Instead it looks like LCD RW is connected to J15A:Vd (5V)