Grief getting LCD to work

Testing/Troubleshooting
1

Hi all

Firstly thanks to TK and everyone involved with this superb project. Now to the begging stage…  ;D

The Core module seems to work OK (MIOS 1.8 uploaded) and is showing loads of random controller and note events which I take is normal when the analog inputs aren’t clamped to ground.

Problem is when plugging in the LCD, the PIC appears to continuously reset. Am pretty sure the LCD is wired correctly as the 16x2 I’m using has the pins clearly marked and I managed to pull a datasheet for it off the web. (Vikay 2322) I tried another LCD but am experiencing the same issue. Am assuming there has to be a fault somewhere on the core module but for the life of me cannot figure out what it could be. The PIC is a 18F452 as sold by Mike’s. Bridge 6 is wired between pin 28 and J4’s SC pin.

When plugged in the LCD shows a row of black bars in the first line.

Breakdown of MIDI msgs are as follows:

(a) LCD not plugged in

0008A1B1  1  –    BD    4A    42  14  —  CC: Brightness       

0008A1B2  1  –    BE    4A    41  15  —  CC: Brightness       

0008A1B3  1  –    BF    4A    42  16  —  CC: Brightness       

0008A1B5  1  –    B0    07    42    1  —  CC: Volume           

0008A1B6  1  –    B1    07    42    2  —  CC: Volume           

0008A1B7  1  –    B2    07    42    3  —  CC: Volume           

0008A1B8  1  –    B3    07    43    4  —  CC: Volume           

0008A1B8  1  –    B5    07    41    6  —  CC: Volume           

0008A1B9  1  –    BC    07    40  13  —  CC: Volume           

(b) LCD plugged in

0008E188  1  –    FF    –    –  –  —  System Reset         

0008E7F6  1  –    FF    –    –  –  —  System Reset         

0008EE65  1  –    FF    –    –  –  —  System Reset         

0008F19D  1  –    FF    –    –  –  —  System Reset         

0008F4D3  1  –    FF    –    –  –  —  System Reset         

0008F80B  1  –    FF    –    –  –  —  System Reset         

0008FB2F  1  –    FF    –    –  –  —  System Reset         

0008FB42  1  –    FF    –    –  –  —  System Reset         

2

Hi,

such a behaviour was never reported before. It would be interesting, what happens, when you are loading the lcd7_clcd driver example application into the core?

(Propably you have to upload the code with the first level BSL, within 2 seconds after power-on)

Best Regards, Thorsten.

3

Wow, thank you so much for the quick reply. I will attempt this tomorrow when I get the chance and post the result, bed is calling. No doubt I probably messed something up on the core module…  ???

Guten nacht

Asbak

4

Uploaded MIOS 1.8, powercycled, then uploaded MB64_v2_4, powercycled, then uploaded lcd7_clcd via MIOS Studio. Results as follows:

TIMESTAMP IN PORT STATUS DATA1 DATA2 CHAN NOTE EVENT             

00000DB6  1  –    F0  Buffer:    8 Bytes  System Exclusive     

SYSX: F0 00 00 7E 40 00 01 F7

00001DD9  1  –    F0  Buffer:    8 Bytes  System Exclusive     

SYSX: F0 00 00 7E 40 00 01 F7

00002DFB  1  –    F0  Buffer:    8 Bytes  System Exclusive     

SYSX: F0 00 00 7E 40 00 01 F7

00003E17  1  –    F0  Buffer:    8 Bytes  System Exclusive     

SYSX: F0 00 00 7E 40 00 01 F7

00004E39  1  –    F0  Buffer:    8 Bytes  System Exclusive     

SYSX: F0 00 00 7E 40 00 01 F7

   

After loading MB64_v2_4 I could see loads of controller msgs being generated (to be expected because the AIN’s aren’t grounded?), but after uploading lcd7_clcd all I see are “SYSX: F0 00 00 7E 40 00 01 F7” messages.

5

(short sidenote: MIOS only has to be uploaded once, every application upload will overwrite the previous one)

After loading MB64_v2_4 I could see loads of controller msgs being generated (to be expected because the AIN’s aren’t grounded?)

of course, but this shouldn’t be the problem, why the LCD isn’t working

but after uploading lcd7_clcd all I see are “SYSX: F0 00 00 7E 40 00 01 F7” messages.

The core gets a watchdog timer reset. Since the LCD driver can handle with timeouts (eg. if the LCD is endless busy), it seems that your display doesn’t react like expected.

You could try the following: disconnect the D7 line (at pin 40 of the PIC) - does the reset still happen? It shouldn’t

Then you should check the control lines to the display again (RS, RW and E) - if one or more of these lines are swapped, such random effects can happen!

Another point is, that the pin markers could be wrong (am I too persimistic? No, in fact I got such a display some time ago, it was a 1EUR display from Pollin ;-)) - if you are unsure, just try all combinations for the RS/RW/E pins. Or better: just connect them in the same order like shown here: http://www.ucapps.de/mbhp/mbhp_lcd.pdf, because normaly the order of control/data pins is always the same, I don’t know any display which has a different pin order

Best Regards, Thorsten.

6

Hello again Mr Klose

I tried your suggestion to remove D7 but still, it didn’t work so I decided to remove the connections in sequence until the resets stopped. (Was too scared to break something to try this earlier, but desperate events called for desperate measures  ;D

I removed data 7 - 0, then E, RW, RS, VO, VD, VSS until I was left only with the LCD backlight. Still the PIC was resetting. After unsoldering the B - ,  errors stopped. (No surprise because only B+ was still connected.) Then I resoldered all the data connections and E, RW, RS, VO, VD, VSS but left the backlight off. Rebooted the PIC and…

SUCCESS!! (albeit it with no backlight) - Not sure why this happened but can only guess that maybe the powersupply isn’t strong enough?  ???

Once again, thank you very much for the advise and your efforts to make a brilliant home project possible for us not so talented guys  :slight_smile:

Best Regards

Hugo

By the way, if anybody is interested, here is the layout for the Vikay 2322 16x2 LCD:

(When looking at LCDFrom the front the layout as follows)

PIN:

14 | 13 | 12 | 11 | 10 | 9 | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 15 | 16

  1. VSS

  2. Vdd

  3. V0

  4. RS

  5. R/W

  6. E

7~14. DB0 –> DB7

  1. B-

  2. B+