LCD not working, core possibly not either

Testing/Troubleshooting
1

Ello.. me again ;D

I plugged in my lcd, and nothing happens when i apply power, the backlighting doesnt come on (and no characters are displayed).

I programmed the PIC by using the JDM programmer over the connection to J3 on the core, which verified that the bootloader was loaded properly.

Should the LCD light up when power is applied to it, regardless of if everything is set up correctly (as long as power is being supplied to VDD and VSS and LED- and LED+)?

I think something is drastically wrong with my circuit - i sent the following sysex string:

F0 00 00 7E 40 00 0D 02 00 0B 0A 00 00 00 01 00 00 00 00 F7

in order to see if the PIC thought there was an lcd connected, but i got no response.

I’m getting fed up again  :-/

Thnx!

EDIT: Damn i forgot to say - i checked the connections for the LCD and thats all fine, i checked the voltage across Pin 1 and 2 of the LCD (Vss and Vdd) and that was a healthy 5v, as was the voltage across pin 15 + 16 - A(LED+) and K(LED-).

2

You should probably check the schematics for the LCD. It should light up even if you don’t have a PIC connected! If you have the right voltages the pinning is probably wrong.

(I hade the wrong schematics for mine and had exactly the same problem.)

3

Hey Ello!

Does the PIC send the (F0 00 00 7E 40  00 F7) string when you boot it up?

I would try troubleshooting the PIC chip first in order to isolate problems. When the PIC is working properly I would move on to troubleshooting the LCD.

Also for the LCD check the Contrast pot and make shure it is working properly. If it is bad it might already be on, but not visible.

In order to bypass the LCD (Thorsten had suggested)

Remove the D7 and +5V line - in this case the LCD driver should get a timeout and ignore all following calls to MIOS_LCD_*

I would check the PIC first, examine pinouts for incorrect wiring, and let me know what happens.

Good Luck!

-Sephult

4

I have to add that my pinout for the LCD was not the same as the LCD jumpers on the core!!

I would also double check these like kejace suggested.

-Sephult

5

YO!

No the circuit doesnt send any sysex on start up, which makes me think there is a problem some where on the board (i don’t get a sysex string even if the lcd is not connected).

As for the LCD, i tested it by plugging my cable in and checking the connection between the bottom of the core board (where the jumper pins where soldered) and each individual pin on the LCD.  Hard work when the pinning isnt straight forward!  ::slight_smile:

Right.. i’ll go check the connections on my core again :slight_smile:

6

YO again!

OK so it must be a wiring problem, let me know what you find with the circuit wiring, when we get that solved then the LCD is the next step.

Also check your configurations on MIDI-OX

Thorsten suggested 2048*4 at 700ms after F7 delay, with delay set at zero. Also go to devices uncheck the attach midi in to midi out ports, open the midi out port in the top right cell and remove the midi input. This configuration seems to be the best for MIDI-OX.

Good luck on troubleshooting!

-Sephult

7

Hey I saw your previous post!

are you using the same crystal as posted. I believe it is the wrong cut, which might be your problems. I also notice your voltage was initially way high. Did you have your LCD connected at that time? I have burned out an LCD before because of a PSU short, so maybe this will help.

The xstal however looks suspicious :slight_smile:

-Sephult

8

Hey mate :slight_smile:

I didnt have anything connected at the when i was getting strange voltages, because i was just testing the volts between pins on the IC.

Yeah i’m using that same crystal, i was begining to get the feeling that that was the problem!  :-/

I checked the connection between pin 3 (+5v) of the 7805 and B+ / Vd of the core lcd jumper pins, and thats fine, so presumably the LCD *should* light up when i apply voltage, even if it displays nothing right?

I’ll try find another crystal (my local supplier is out of stock) but farnell offers 3 x 10 mhz crystals and i dont know which are serial and which are paralell cut -

http://uk1.farnell.com/Search/level_5.jhtml?PRODID=47684&SKUID=45669

^ That’s the order page, but it doesnt say (neither does the datasheet) whether crystals are serial or parallel cut  :'(

9

The xstal should have some sort of rating for capacitance, this is how you know which one is correct. As for the LCD, have you tried testing the contrast pot? I am unsure about hooking it to the 5v without the PIC booted.

I will test it out tomorrow and let you know.

-Sephult

10

The crystal i use is parallel cut.

But the circuit still doesnt work  ??? ??? ??? I have no clue why not.

11

Just use a multimeter- check the ohm ratings between the pins and see if you can get the correct resistance.

As for the circuit not working, Check your wiring again

j3 on the core

In normal use, the pins have to be shortened with 5 jumpers, otherwise the PIC will not run!

-Sephult

12

I have a spare PIC16F874 and 20 mhz crystal.  would it be possible to burn a firmware (after i’ve replaced the crystal) just to test the midi out (like send a sysex on power on)?

That way i would know if it was my crystal thats causing the problems?

I started building my box last year using the .pdf midibox 16 guide and that didnt work, but that could have fried my lcd i guess?

Well if the midi output works with my old pic, then i’ll buy a new lcd :smiley:

13

yes! try with a PIC16F! and so you’ll see if it works with the crystal!

14

Well i tried with PIC16F874 and 20mhz crystal, and that didnt work either, so there has to be something wrong with my circuit.

I’m checking my components now.

C6 is 33nF (resin dipped code “333” so i think thats 33nF?) instead of 330 nF. Could this be the source of my problem?

That’s all i can see thats wrong with my circuit  ???

15

I tested the circuit again with the correct C6, and it still doesnt work.

I’ve run out of ideas, can anyone help please?

When looking at the soldering is there anything specific to look out for - other than solder connecting two things that shouldn’t be connected?

I wish my digital camera was good so i could take a detailed picture of my board so someone could get me advice!

16

Please try the following:

  - use the PIC18F452 (you wrote that IC-Prog verify passed…)
 

  • use a 10 MHz crystal
     
  • ensure that C1 and C2 is 33pF (pico-farad)
     
  • plug the 5 jumpers into the J3 socket
     
  • connect a LED+220 Ohm resistor between the Tx pin of the PIC and ground. Cathode (the short leg) connected to ground
     
  • the LED should lit at power on. if MIOS has not been uploaded yet, it should flicker every 2 seconds
     
  • disconnect the LED and try to upload the operating system. If this doesn’t work, check the MIDI In port like descriped here: http://www.midibox.org/cgi-bin/yabb/YaBB.cgi?board=troubleshooting;action=display;num=1055726526
     
  • disconnect the LED after the test and try the upload again

Most important: so long as MIOS has not been uploaded correctly, the LCD will not be initialized!

Best Regards, Thorsten.

17

Thanks for the suggestion TK!

You caught me just as i was about to sling my pcb at the wall hehe.. *calms down*

Yes my PIC18F burns fine everytime, i shall solder the 10 mhz crystal back on, then follow your instructions.

Are those instructions for the bootstrap loader or test program (test_tx.hex)?

Thanks!

18

The instructions are for the bootstrap loader, all precompiled .hex files for the PIC16F are not working with a PIC18F.

So, for the PIC18F the strategy is to get the bootstraploader running first. Once it works, you don’t need the JDM anymore.

Thereafter upload the operating system (MIOS V1.3) via MIDI - also this has only to be done once.

Thereafter try some MIOS applications.

Best Regards, Thorsten.

19

Right. I tried the test and the led didnt light up.

Does this mean my programmer isnt working properly? Or could it be that my xtal is wrong?

I’ve just discovered i got the same LCD as the guy from this post:

http://www.midibox.org/cgi-bin/yabb/YaBB.cgi?board=troubleshooting;action=display;num=1048869713

So if i got problems i’ll study that! YAY!

20

I asked Nat to do the test also (he is having problems with his core - due to a serial cut crystal).

Does that mean my crystal is at fault? If it is would part number FY78 (from www.maplin.co.uk) be suitable?

Thanks! :wink: