Re: [N8VEM: 14609] SBC V2 build not working

[Douglas Goodall <douglas...@mac.com>]

Wayne,

Oh yea, post a picture of your populated board front side so we can see the parts and the jumpers.

Douglas

On Sep 9, 2012, at 3:01 PM, opticpow <wa...@ingram.net.au> wrote:

Hi all,

I completed my build yesterday and unfortunately I haven't got my board working as yet.  When I power on, I get no output on the serial console. I have read this great thread on troubleshooting https://groups.google.com/d/topic/n8vem/0MRwLgNxEPY/discussion These are the steps that I have done to try and diagnose the problem:

1. Confirmed that I have clock on the pin 6 of the cpu and pin 16 on the 16550
2. checked that all ICs are seated properly and no pins are bent over
3. inspected my soldering for obvious problems
4. tried re-burning the rom a few times
5. checked that no magic smoke was released, and no ICs are warm to touch
6. based on the discussion on the link I referenced above, I checked the reset circuit which I believe could be the problem. When I power on the board, the reset line goes high and stays there. I'm not very experienced, but looking at the schematic, I'm guessing reset should stay high until C2 charges, then be pulled low?

Board Configuration:

• All jumpers are in their default state except for K6 & K8 as I'm using a flash chip
• For U2, I'm using a AM29F040-90PC from here http://www.ebay.com.au/itm/AM29F040-90PC-Manu-AMD-Encapsulation-DIP-32-4-Megabit-524-288-x-8-Bit-CMOS-/120922012708?pt=LH_DefaultDomain_0&hash=item1c27837c24
• I'm programming U2 with one of these http://www.ebay.com.au/itm/New-G540-USB-Universal-Programmer-EPROM-FLASH-MCU-GAL-PIC-G450-Programmer-agz-/160793467243?pt=AU_B_I_Electrical_Test_Equipment&hash=item257009996b It seems to work well, has the above flash chip supported in it's gui, and I can pull the flash chip out of my board and verify the rom image correctly
• I'm powering the board via a PC power supply
• CPU clock it 8Mhz
• using 74LS chips
• I'm just using a normal led for D1, with the anode in pin 1. It lights when the power is applied
• I'm using this ROM http://n8vem-sbc.pbworks.com/w/file/47464605/RomWBW.zip

As I stated above, I do believe the reset could be issue. If someone could kindly describe this part of the schematic, I think that will help me diagnosing the issue.

Thanks,

Wayne.

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