Help! I need some keyboard troubleshooting.

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Help! I need some keyboard troubleshooting.

Postby Juz10mac » Jan Wed 10, 2007 6:38 pm

Hello,

I'm new here. I finished building my Replica 1, but am having problems getting the keyboard to work. I have tried four different PS/2 keyboards. When I apply power the keyboard LED indicators light up then go back off, just like when a PC is booted. Each time the machine comes up with the @ symbol until I hit reset then I get the slash. The indicator blinks; I tried using the keyboard, but I simply get no response. I made sure the jumper was set to PS/2 and not ASCII. I checked and rechecked my solder points, but to no avail. I also checked continuity on the keyboard decoder and the PS/2 connector. I found two pins on the connector that do not seem to be connected to anything. Is this correct? The solder points are good, so if there is a problem it is with the board or the PS/2 socket. Does anyone have any ideas? And could someone tell me where each pin on the PS/2 connector is supposed to lead. I couldn't find a circuit diagram. If there is a bad print on the board I could try soldering a bypass wire (this is why I am asking). Does this make sense? I appreciate any help anyone can give.

Thank you very much,
Justin
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Postby cheese1113 » Jan Wed 10, 2007 6:56 pm

Can't remember if you need it on or not, but is caps lock on?
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Postby Juz10mac » Jan Wed 10, 2007 8:15 pm

That's interesting. I tried turning on the caps lock but it won't turn on. I still have no response from the keyboard and the caps lock LED won't turn on when I press the caps lock key. I tried holding down shift, but still no luck.
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Postby cclaunch » Jan Wed 10, 2007 8:47 pm

It appears from what I can tell that the chip at U3 is responsible for decoding the PS/2 keyboard. I would look at all the connections at and around there, plus look carefully to be sure that you don't have bent-over pins on the inserted IC.

If you can set up a serial connection to a PC, you can verify more of the functionality -- as it is you know that the basic system works, it enters the Woz monitor and that the video output is okay. Using serial, you could type in from your PC. Don't forget to caps-lock on the PC! Based on what works and doesn't, you will narrow down the area to check.

Also, there have been many who have had one or two bad PS2 keyboards, plus problems with the fancier ones that add extra buttons intended for modern Windows capabilities. I was lucky and had the first simple keyboard I attempted work properly.
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Postby vbriel » Jan Wed 10, 2007 9:47 pm

Ok, this can get difficult because the ATMEGA8515 intercepts the keyboard signals before sending them out to the 6821. To test your replica 1, try and see if you can get communication with your serial port or your USB if you have it. Remember caps lock on the PC side! See the manual for setting up the serial communication.

It is normal for the lights to come on when power up, then go back out. That tells us that you are getting power to the keyboard. I didn't program the keyboard to have the lights come on when you press caps or numlock, sorry but that wouldn't helps us anyways.

Another test you can do is to use a voltmeter and see if you can see it change when you press different keys. Take a voltmeter and put the black probe into the mounting hole in a corner of the replica. Place the red probe on pin 14 (pin 1 is marked with a dot). Turn on the replica 1 and press RESET. While holding the red probe in one hand, type different keys on the keyboard and see if the voltage changes. That is the keyboard data bit 0. If this works, try the same thing on the 6821 pin 2. You should see the voltage change on pin 2 as well. Report back what you find and we can go from there.

Vince
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Postby Juz10mac » Jan Wed 10, 2007 10:55 pm

I followed all the steps in HyperTerminal as described in the Replica1.pdf manual. When I press reset I get a backslash and a blinking underscore. I turned caps lock on and tried to type, but it still won't type. So, for some reason the Replica 1 is not getting the ASCII keyboard instructions no matter what the source?

I also did the voltage test you suggested on the ATMEGA8515 and the 6821. When I pressed keys on the PS/2 keyboard the voltages changed on both pins (14 for ATMEGA8515 and 2 for 6821). The voltages went high and low (0V and 4.45V) for each depending on what key was pressed.

Thanks
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Postby vbriel » Jan Wed 10, 2007 11:32 pm

Ok great, the ATMEGA8515 and the ATMEGA8 appear to be operating ok. The data is getting to the 6821 and then it stops. The backslash means that the 6502 is functioning and it can read from the Woz monitor and output the backslash on reset. Now, does the cursor stay on the same line as the backslash or drop underneath on the next line. So, when you press RESET does it look like this:

\@

or does it look like this:

\
@

Let me know. Also, I know I beat this like a dead horse but check the sockets of the 6821, 62256 RAM, 28C64 and 65C02 and make sure you have all your solder connections. You wouldn't believe how many times that has happen to me.

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Postby Juz10mac » Jan Thu 11, 2007 12:05 am

I checked all of the solder connections. Externally, they look good to me; all IC pins are in the sockets and all sockets are soldered to the board at each pin.

I'm assuming the _ (underscore) is the cursor in HyperTerminal (it blinks). Here is what I see in HyperTerminal:

\_

Here is what I see using a video monitor:

\@

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Postby Juz10mac » Jan Sun 21, 2007 6:00 pm

Still no luck.

I replaced the SRAM as a troubleshooting step to see if I had a bad IC. It behaves the same whether or not the SRAM chip is installed. the cursor does not drop down to the next line and the Replica I will not accept input from the keyboard. I have noticed that on occasion, after I press reset, instead of being presented by a "/", the screen will be flooded with "////////". Hitting reset again stops this. This hasn't happened much, but I thought it worth reporting in case there is any clue to the solution here. I have not given up yet.

Thanks,
Justin
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She Works!!!

Postby Juz10mac » Jan Sat 27, 2007 5:08 pm

I finally got it working! This has probably been the most rewarding troubleshooting experience I have ever had, not to mention the most frustrating. After rechecking everything I could think of again and again and redoing about half the solder points, I found the problem. There was a bad connection on the board; a printed circuit path stopped short of reaching a metal through-board hole (where the path is stopped and continued on the other side of the board). I don't know if this was an original defect in the board or if I had inadvertently damaged it when putting it together (I suspect the latter because of its close proximity to a rough spot on the board, where it looks as though the soldering iron briefly came into contact with the board). It was easy to fix. After a dab of solder and finding out that the keyboard I was using was not going to work, presto! Thanks for all of your help and suggestions. It's always good to have a happy ending on a troubleshooting forum topic.

Thanks A Million!
Justin
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Postby cheese1113 » Jan Sat 27, 2007 8:13 pm

Congratulations! Hope you have fun with your replica!
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Postby vbriel » Jan Sat 27, 2007 8:39 pm

Congrats Justin. I'm glad you figured it out. Where was the missing connection at, if you can describe? I'd like to look over the replica 1 board blanks and see if this was in any boards or something that happened to yours.

I've not seen a bad board yet but it can happen. Machines do make errors in machining, just not that often.

Glad you stuck it out and found the problem, makes your replica that much more fun to enjoy.

Vince
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Postby Juz10mac » Jan Tue 30, 2007 12:16 pm

I'm sorry I didn't get back to you sooner. I've been devoting every free moment to learning 6502 assembly ;). The bad spot was where a printed circuit path is continued on the other side of the board (one of the tiny metal holes). This particular one is under the 74LS138 to the left side and is the one closest to the center of the chip.
I bought a little 5" B/W TV set from Academy Sports and Outdoors that I'm using for a video monitor. It's pretty slick if I do say so myself. It's a lot of fun and I'm learning a lot, too.

Justin
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Postby a1 » Feb Sun 18, 2007 11:05 pm

Hello.
Just got my replica 1 SE built and am having some problems too.
Sometimes BASIC will execute and sometimes not.
Sometimes when it does, it doesn't recognize numeric keys.

When I RESET, I get the \ with @ on the second line?
Is this correct. If so, what else could be wrong?
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Postby vbriel » Feb Mon 19, 2007 7:02 am

One of the first things to check is all of your solder connections. Check each chip, one pin at a time and make sure all solder contacts are good.

Try another keyboard. Reseat the EEPROM.

Just a few of the things you can try.

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