Atmega 644 and/or 18F14K50 problem

[funkystx]

I just finished building the Synthex 3.2 kit and just began testing it. I ran into some issues, so I checked this forum for advise and solutions. That brought me a little bit further, but now I'm stuck at troubleshooting. Let me just break down the steps that I've gone through so far:

- I hooked up the LCD, keyboard, MIDI-ports and 32-input PCB to the main board
- I connected the main board with my PC via USB
- Windows XP recognized and installed drivers for the new USB device / MIDI-ports
- LCD back light came on, but nothing showed in display
- I followed the 'LCD-topic' instructions and tried to increase the contrast via the menu (hold LEFT for few secs, then once RIGHT, hold UP to increase) > no result
- I disconnected USB power
- I connected LCD pin 3 to pin 1
- I reconnected USB power
- LCD now shows black boxes on the upper row
- Windows says 'unknown USB device'

According to the 'LCD-topic' black boxes indicate there's a problem with the Atmega 644, so I checked LCD pins 4-14 against the connection with the Atmega. My measurements sometimes deviate from the 3.2 schematics, as some LCD pins connect with multiple pins on the Atmega. Maybe I messed up the pin numbers, since it's hard to match those against the schematics. Or is there an interconnection inside the Atmega? Do I need to remove the Atmega before I measure the pins connected to the LCD?

Besides the Atmega issue, Windows XP keeps on failing to recognize my device. So far I tried several different USB ports on 3 different computers, changed the USB cable, but no result.
As I understand correctly, it's the 18F14K50 that's responsible for establishing an USB connection with the computer. It worked the first time and now suddenly it doesn't any more. Can it be a malfunction of the 18F14K50? Or are both problems connected and should I concentrate on the Atmega instead?

Any help with these issues is highly appreciated!

Rens

[dmitri]

According to the 'LCD-topic' black boxes indicate there's a problem with the Atmega 644, so I checked LCD pins 4-14 against the connection with the Atmega. My measurements sometimes deviate from the 3.2 schematics, as some LCD pins connect with multiple pins on the Atmega. Maybe I messed up the pin numbers, since it's hard to match those against the schematics. Or is there an interconnection inside the Atmega? Do I need to remove the Atmega before I measure the pins connected to the LCD?

Besides ground and power pins no pins in Atmega are interconnected. You have shorts.

Besides the Atmega issue, Windows XP keeps on failing to recognize my device. So far I tried several different USB ports on 3 different computers, changed the USB cable, but no result.
As I understand correctly, it's the 18F14K50 that's responsible for establishing an USB connection with the computer. It worked the first time and now suddenly it doesn't any more. Can it be a malfunction of the 18F14K50? Or are both problems connected and should I concentrate on the Atmega instead?

You most likely have shorts/breaks/loose connectors/loose soldering.

[funkystx]

Besides ground and power pins no pins in Atmega are interconnected. You have shorts.

You most likely have shorts/breaks/loose connectors/loose soldering.

Thanks for the quick reply! I'm gonna check all related components and soldering in a few days.
I'll post my findings here later.

[kupooglop]

If any of the pins that go to the lcd are not connected, you will get upper row black boxes. The pic(18F14K50) might actually be working. Since the display doesn't work, you have no way of knowing because you can't navigate the MD menus without the lcd. (unless you have magical psychic powers or something...) I just had the same problem with the upper row black boxes. In my case, it had nothing to do with the Atmega or the pic. It was because one of the lcd ribbon connector pins broke loose from the circuit board while I was assembling the components.

[funkystx]

Alright, I took the time to clean and examine the PCB and components. To summarize my checks:

- ICs, capacitors, diodes, LED polarity checked > okay
- PCB soldering checked > okay
- Capacitors capacity values checked > okay
- LCD ribbon cable soldering, connector/socket are all okay
- LCD pins 1,5,7,8,9,10,16 connect to gnd - pins 4,6,11,12,13 connect to Atmega pins 16,17,19,20,21 (no shorts > that was actually ground I measured earlier!)
- LCD pins 2, 15 receive power, R30 measures correct value - pins 3 and 14 are connected thru R21, R22 + C12 checked out okay - no shorts
- USB connector pins 1,4 (power/gnd) okay - pins 2,3 connect to PIC pins 18,19 - R27, C5 and PIC pin 17 okay
- PIC pins 10,12 connect to Atmega pins 14,15 - pins 2,3 connect with crystal 12 Mhz and C20,C21
- Atmega pins 12,13 connect with crystal 20Mhz and C18,C19
- keyboard push buttons work correctly - leads/pins connect with Atmega, D5,D6 and R23-R26 okay
- U3, R3-R6, R20, D7 connections checked out okay
- MIDI LED connects with Atmega pin 27 thru R7

Furthermore I gave it another try to connect with my computer via USB and occasionally Windows recognizes the USB device/MIDI ports again.
But the black boxes on the LCD remain (still got pin 3 wired to pin 1 for max brightness) and the MIDI LED doesn't blink at all.

So is there anything I might have overlooked or someone with advise on how to proceed? Please let me know guys.

[Firelord]

So is there anything I might have overlooked or someone with advise on how to proceed? Please let me know guys.

You might have some flux left on your board from soldering. Try cleaning it thoroughly.

If this doesn't help, post photos of your board (from both sides). This will allow me to evaluate the possibility of potential problems.

[funkystx]

You might have some flux left on your board from soldering. Try cleaning it thoroughly.

If this doesn't help, post photos of your board (from both sides). This will allow me to evaluate the possibility of potential problems.

I used some special electrical cleaning solvent and a toothbrush to clean all soldering, so there shouldn't be any flux residue left.
As you requested, I took some photos of my PCB from various angles:

MD56_Sv3.2-01tn.jpg

MD56_Sv3.2-02tn.jpg

MD56_Sv3.2-03tn.jpg

MD56_Sv3.2-04tn.jpg

You can download larger sizes of these photos here: http://www.megaupload.com/?d=J5XVF6JU

Looking forward to your reply (or anyone else who can contribute in solving this mystery! )

[funkystx]

Oh, and here's also a photo of the LCD pin soldering with temp max brightness mod:

MD56_Sv3.2-05tn.jpg

[Firelord]

The board looks good. However,

1. Remove the green wire on your last photo! Shorting 1 & 3 is only meant for testing the LCD.
2. I don't like how your PIC is sitting in its socket. Carefully remove it, maybe clean the pins with alcohol and place it back.

[r0bbie]

Hi,

I don't think your boards soldering looks great (sorry Firelord
To bad you have posted 3 pics of the component side and only one of the solder side, the most important one in this case.

You have a lot of "cold joints", that is, yes there is solder on the pin of the component and it touches the circuit-board, but it didn't got enough time to flow and make a good connection.

If you look at your first picture, and look at the third resistor from top, at the left from the Atmega, you see that the solder has flowed trough the board to the top, this is how all your solder joints should look.

So here's what to do, carefully remove your chips from the sockets ( they don't like heat).
Re-solder every pin in the following way;

Put the (clean) tip of your soldering iron on the pad at the same moment add a little more (multi-core) solder, leave the tip at least 3 seconds on the pad, clean the tip of the iron again and move to the next pad.

Repeat the above until all the pads are done.

Inspect the board carefully before placing chips and applying power, even better, post pictures after for evaluation.

Good luck

Rob