LCD Firmware Problem

B

Ben967

Member
Hi,
I wondered if you guys could help me, I have recently bought a 20x4 lcd display which uses the hd44780 driver chip. I also bought the lcd firmware chip from techsupplies and have followed the picaxe datasheets exactly to connect the fimware chip to the lcd, but have had no luck, although the lcd works fine when being controlled directly from a picaxe 20m.
Any help much appreciated! :)
 
R

russbow

Senior Member
Ben,

Your program / circuit would be useful. Not quite sure what you mean when you say "works fine when being controlled directly from a picaxe 20m."
 
B

Ben967

Member
russbow said:
Ben,

Your program / circuit would be useful. Not quite sure what you mean when you say "works fine when being controlled directly from a picaxe 20m."
Click to expand...
Sorry I mean the lcd works perfectly when connected to a picaxe 20m using hippys connection instructions and code,
http://www.hippy.freeserve.co.uk/picaxelc.htm but when connected to the firmware chip from techsupplies, following their connection instructions, the lcd does not work at all.
 
M

manie

Senior Member
Do you have your FRM010 chip jumpers for Baudrate and 4-bit or 8-bit set up correctly ?
That is, have you pulled pins 9/10/11/12 low or not etc. Also, turn your 5k/10k contrast trimpot around from extreme to extreme, on mine I have to turn the pot to one extre,e to see the display.
 
B

Ben967

Member
I have tested contrast levels at the extremes (eg 0v and 5v) but the jumpers must be where the problem lies. Do you know how they should be set for a 20x4 lcd at 2400 baud?
Thanks again
 
B

Ben967

Member
Ok have gone through all manuals again and checked wiring, all seems fine but the firmware chip still refuses to work!
 
R

russbow

Senior Member
Ben,leave legs 11, 12 & 13 open and earth leg 10. This should run at 2400 baud. If you use serout 7, T2400 then you must preceed with high7 ( or whatever pin you are using. I am using the circuit in the chip leaflet with the above settings and all works nicely.
 
B

Ben967

Member
I have tried tying the various jumpers to ground but still no luck, I think the problem is that the firmware chip isnt actually receiving the serial data. I have the firmware pin 3 connected to the picaxe output pin via a 1k resistor as the manual states, I also have an LED connected to pin 17 of the firmware chip to show when serial transmission is in progress, but it never lights up, even when I know the picaxe is outputting serial data.
If anyone knows what I am doing wrong I really appreciate the help! :D
 
hippy

hippy

Ex-Staff (retired)
Are you sure you are actually sending data to the FRM010, you've not got the wrong wire connected, the 1K not connected to the right PICAXE output pin, the right polarity and baud rate selected ?

Posting your PICAXE sending code will help.

You can check the PICAXE is sending data by using a LED+R; connect between output and and 0V for Nxxxx baud rates or 5V and output pin for Txxx baud rates and it will flash when data is sent.

Once that's working, move the 'testing wire' from PICAXE output to the physical 1K leg on the side nearest the PICAXE output; it should again flash when output is sent.

Disconnect this 'testing wire', remove the R from LED+R ( so LED direct to 0V or 5V ) and put the 'testing wire' to the 1K leg nearest the FRM010; it should again flash when output is sent. Be careful not to connect that LED by itself to anything else or you'll blow it up with too much current and could cause other damage.

Being very careful not to touch any other leg you can put the 'testing wire' to leg 3 on FRM010; it should again flash when output is sent.

If all that works then the FRM010 is receiving serial data so either the data being sent isn't right ( wrong baud rate, wrong polarity ) or the FRM010 isn't wired up right.
 
hippy

hippy

Ex-Staff (retired)
Also ... what happens when you disconnect from the PICAXE and connect Leg 10 of the FRM010 to 0V ( "jumper 1" ) ? This should display a welcome message on the LCD.
 
B

Ben967

Member
Have tested with an LED like you said, the LED fails to flash when placed on the firmware chip input (pin 3) but lights up fine when connected to the picaxe output pin. Also I tied the welcome message jumper to 0v, but still get nothing on the lcd.
 
hippy

hippy

Ex-Staff (retired)
Seems you have multiple issues; serial data not reaching the FRM010 and the FRM010/LCD not wired correctly, or maybe the FRM010 isn't working, isn't powered or some other hardware problem.
 
B

Ben967

Member
The data is definately getting to the lcd as I have tested with an LED on the data lines, but all i can get on the lcd screen is a line of dark squares which keep flickering. Anyone have any ideas? :D
 
W

westaust55

Moderator
Ben

are you using the FRM010 chip datasheet or Manual 3 for your FRM010 chip to LCD connections. the FRM010 sheet is correct whereas the Manual 3 has the 4 data lines sequence swapped at the LCD.

Can you upload a clear photo of your circuit. It may help someone spot any wiring errors.
 
hippy

hippy

Ex-Staff (retired)
Ben967 said:
The data is definately getting to the lcd as I have tested with an LED on the data lines, but all i can get on the lcd screen is a line of dark squares which keep flickering. Anyone have any ideas? :D
Click to expand...
That's somewhat different to your earlier post; "when connected to the firmware chip from techsupplies, following their connection instructions, the lcd does not work at all".

But I cannot see how data can be getting to the PICAXE side of the 1K to leg 3 of FRM010 and yet not to actual leg 3 itself which the LED test should have shown. Either the LED used won't light at all with 3V-5V / 3mA-5mA ( unlikely I'd have thought ) or there's some other testing error.

@ westaust55 : Manual 3 which I'm looking at seems the same in wiring LCD to FRM010 as the FRM010 datasheet; D4(11) to leg 6 of FRM010, through D7(14) to leg 9, RS(4) to leg 1, E(6) to leg 2.
 
B

Ben967

Member
I have used the Firmware datasheet and followed those wiring instructions exactly. Earlier the lcd was not getting data at all, but now I have rewired the circuit again following the firmware datasheet and the lcd is now receiving data, I have checked the serial input to the firmware and the 4 data line outputs to the lcd with a LED and it lights up now, but all I can get on the lcd screen is a line of black boxes which flicker.
 
W

westaust55

Moderator
hippy said:
@ westaust55 : Manual 3 which I'm looking at seems the same in wiring LCD to FRM010 as the FRM010 datasheet; D4(11) to leg 6 of FRM010, through D7(14) to leg 9, RS(4) to leg 1, E(6) to leg 2.
Click to expand...
Ah yes, page 34 also showing FRM010 is correct.

Its pages 35 and 38 which show LCD pin 14 as DB4 ( but correct is DB7)

problem of working from memory :eek:
 
C

cactusface

Senior Member
More LCD....

Hi,
A line of black squares, think that means contrast too high, turn it down, what can you see now?? But what do I know, not got my own project up and running yet!

Just discovered my old Z80 trainer, used a Maxim 7218 this can drive 8x 7 seg displays from an 8 bit port plus a couple of control bits. Now they do a serial version, ideal if you only need a temp or time output (OK a few hex char$ too).
Regards
Mel
 
B

Ben967

Member
Hi, Thanks for your help, I have tried contrast at all levels and the only thing i get still is a line of black squares, which flicker every time i send more serial data to the lcd
 
hippy

hippy

Ex-Staff (retired)
The 'single line of black blobs' is usually indicative of the LCD having not been initialised properly. In my experience this usually points to the LCD having been mis-wired, though it could also be that the LCD module is not fully HD77580 compatible.
 
You must log in or register to reply here.
Top