LCD do display - but pins check out

[Scampy]

Guys, I'm debugging the mistakes I made when prototyping a PCB. I say I made, the schematic tested out OK in the DRC check, but the board failed to pick up some nets and thus I'm missing a few tracks to some components. However I've trouble shouted through the board and The PIC is running fine, I have comms through an FTDI 232RL chip, and it reads the 18B20 sensor and an corresponding monitoring LED flashes away to confirm the code is running, but the LCD simply lights up with the backlight and doesn't display anything at all.

I've traced the routing for the 4 bit data lines using a multi-meter for continuity, and using a scope I get negative pulses on enable pin, and positive pulses on the R/W pin - these are around 1.2s frequency which seem slow given that the pic is running at 40 Mhz with a 10 Mhz xtal. There are no solid blocks regardless if the contrast is grounded or taken high (or 4k7 placed between it and the 5v rail). If I replace the PIC back on the development board it works fine ! and the schematic for the LCD was taken from the manual for the EasyPIC5 board - any suggestions or further testing I can do.

[Tabsoft]

What are you getting on the RS pin?
Also have you checked the LCD's VDD pin to make sure it is at least 4.5V?

[towlerg]

sorry just reread your post. pulses on r/w doesn't sound correct, rs and r/w crossed?

[Tabsoft]

True.

Looking at the EasyPIC5 manual, R/W is tied to ground so you shouldn't read pulses on it.

RS -- RB4
R/W -- GND
E -- RB5
D4 -- RB0
D5 -- RB1
D6 -- RB2
D7 -- RB3

[Scampy]

Thanks for the replies,

OK here's confirmation on how it's wired.

LCD

1 GND
2 +5v
3 +5v via 4K7 resistor
4 RB4 (RS)
5 GND (RW)
6 RB5 (E)
7 - 10 GND (D0 - D3)
11 RB0 (D4)
12 RB1 (D5)
13 RB2 (D6)
14 RB3 (D7)
15 LED+ 5v via 100R resistor
16 LED- GND


I've attached traces of the pulses I get on RB4 and RB5 (sorry I made a mistake in my previous post) and on two of the data lines. I can confirm that the PIC is running as other functions such as RS232 coms and reading the DS18B20's all work fine. I will try a direct wiring option later (wires direct from the PIC pins), but as I can't find any shorts suspect that there is something else that's srewed on the board.

Moral is not to submit gerbers at 1am in the morning after 14 hrs of drafting the design, but to wait a day and check the design with fresh eyes in the morning ! - This board has so many mistakes in it I must of been totally brain dead !!

[Scampy]

Interestingly, I get the same trace when the LCD is returned to the EasyPIC5 board, but on RB5 the pulses are positive going not negative going !!!