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PCB legend/schematic/parts [message #2462]

Sat, 20 February 2010 17:20

jooks
Messages: 21
Registered: December 2009
Location: sweden

Junior Member

I´ve started building the Bend matrix now and it´s a really great quality pcb! Looking forward to finish it and try it out! I have a few questions though.

Just noticed that the PCB version 2.3.3 I have has some differences from the parts list and schematics.
- R201-R203 is marked 220ohm at the pcb but 330ohm at schematic/parts list. Is the 220 a mistake or a change and which ones are prefered?
- there are 15 0.1uF caps marked at the pcb. 10 in BOM.
- 5 100uF at pcb and 4 in BOM.
- 8mhz resonator is also missing from BOM (but mentioned in the build doc).

Thanks Dann for the trigger mod schematics btw!

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Re: PCB legend/schematic/parts [message #2473]

Thu, 18 March 2010 09:54

smrl
Messages: 23
Registered: February 2010

Junior Member

220 ohms is the correct value for the resistors.

The 8MHz resonator is not needed though there is a spot for it on the board; the internal oscillator is used for the microcontroller. I believe Dann said something about finding the external clock more unstable for some reason. You could always use the external resonator but you'd have to alter the microcontroller for it to do any good.

Otherwise, I think I've got an earlier revision of the board, so I don't know what's going on there.

If there's a spot for a cap, though, I doubt it could do any harm putting one there. Those .1uF caps are mostly bypass caps, placed between VCC & GND on the chips to filter noise where power is applied to the chip.

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Re: PCB legend/schematic/parts [message #2475]

Sat, 20 March 2010 15:27

jooks
Messages: 21
Registered: December 2009
Location: sweden

Junior Member

Thanks for the answer.

I used 330ohms but hopefully it wont matter that much. If it does at least its an easy fix.

I had the same thought about the extra caps. Cant hurt!

An updated bom would be good anyway and the fpd panel layouts also need to be updated since I discovered that the mounting holes for the pcb have been slightly altered in the last pcb rev.

I have the 8mhz resonator since the build doc specified this for the 2.3.2 pcb?

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Re: PCB legend/schematic/parts [message #2502]

Mon, 24 May 2010 13:31

dann
Messages: 829
Registered: December 2002
Location: Austin TX

Senior Member

hey,sorry I've been off the forum for a while...

You guys are right, use the extra caps.

Also, MIDI works much better if you use the 8mhz resonantor. If your kit shipped with the 8mhz res, then your AVR chip has its fuses burned to require the resonantor--so use it if you got it!

330 ohms works sometimes, but some MIDI gear doesnt seem to work as reliably with the bend matrix unless you use 220 ohm resistors (which is the official midi specification).

Also, yes I know I need to post the new FPE files for the new pcb version's mounting holes...

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Re: PCB legend/schematic/parts [message #2705]

Sun, 11 September 2011 12:07

jooks
Messages: 21
Registered: December 2009
Location: sweden

Junior Member

dann wrote on Mon, 24 May 2010 12:31

I finally managed to build this but....when I power it up the all the matrix leds are lit. LCD is stuck on 8.8.8. Shift, clear lights up when I push them and save flashes like it should. All voltages are checked. Is it possible that I have a AVR chip that doesn´t need the 8mhz resonator? I got the parts myself and didn´t know that this had changed. If that´s the case is it possible that it would cause this behaviour?
I can´t desolder the resonator easily otherwise I would have tried that.

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Re: PCB legend/schematic/parts [message #2708]

Sun, 11 September 2011 18:07

dann
Messages: 829
Registered: December 2002
Location: Austin TX

Senior Member

If the AVR is fused for the internal 8mhz clock, then the resonantor won't hurt anything. Just leave it on and turn it on/off with software, as it won't effect the circuit just being there.

More likely I would think the chip has a problem with its code? Or the Reset pin is not high (10k resistor at the top of the atmega32a).

Do you have an avr isp programmer? That would help, you could flash new code on, and check the fuses etc...

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Re: PCB legend/schematic/parts [message #2710]

Sat, 17 September 2011 03:19

jooks
Messages: 21
Registered: December 2009
Location: sweden

Junior Member

I got 4.92v on the reset pin so I guess that is ok?

I have no programmer and no knowledge of such things unfortunately...

Can I just buy a new programmed atmega from you or maybe send it back and have it reprogrammed? (I'm in Sweden)

Thanks for the help!

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Re: PCB legend/schematic/parts [message #2712]

Tue, 15 November 2011 11:06

dann
Messages: 829
Registered: December 2002
Location: Austin TX

Senior Member

Hey... here's my page describing how to program your own AVR chips:

http://4ms.org/?p=64

I'd be happy to send you a new chip, too. But having the programmer is very useful since you can do code updates and try out various versions...

Anyways send me a PM and I'll get your address to ship you a new chip.

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Re: PCB legend/schematic/parts [message #2717]

Sat, 19 November 2011 09:38

jooks
Messages: 21
Registered: December 2009
Location: sweden

Junior Member

Oh, that´s awesome! I´ll eventually get myself a programmer but at the moment I used don´t have the time.
I´ll send you a pm.
Thanks!

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Re: PCB legend/schematic/parts [message #2718]

Sat, 19 November 2011 09:44

jooks
Messages: 21
Registered: December 2009
Location: sweden

Junior Member

Seems to be something wrong with the pm system. It says that there is no member dann when I try to send it.

Anyway, I´d be happy to pay for the chip with paypal!

Thanks!
Erik Anderson
Grubbevagen 107
903 61 Umea
sweden

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