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

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

Wayne,

Here are a few steps I follow. (Some of which you have already done...)

1. Verify power on all +5 pins

2. make sure CPU oscillator is wiggling

3. Make sure clock input to CPU is wiggling

4. Make sure A0 on the flash is wiggling, maybe CE and OE as well

5. Make sure clock input to UART is wiggling

6. See if Tx pin on UART is wiggling after reset, if so serial wiring is likely the problem

7. Use low level test images with short loops (also known as scope loops)

8. When doing low level probing , if a signal is not doing what you expect you may have a problem

where the socket pin does go into the hole, but for some reason solder hasn't reached it, reflow it and check again

(test for continuity between chip lean and trace underneath the board. I have found some of these).

It is possible to have a bad chip. The bottom line if following the basic functions...

CPU clock is running, EEPROM is reading (if not maybe problem with I/O decoder) Check enabled on I/O devices

These are my major thoughts. Be brave, we have all been through this difficult moment and most have working boards now.

You learn a lot in this phase if you engage it enthusiastically.

Regards,

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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