OSSC green led but nothing on the LCD display

[vgdiy]

Hey all, I got back a few 1.6 OSSC pcbs fabricated and assembled. I successfully programed them using a JTAG usb blaster using 0.77 jic file. When I turn it off and then on again, the LCD display backlight and the red led flashes on briefly, then the display and red led turn off and the green led turns on solid. Any idea where to start troubleshooting?

[Morpheus_79]

Did you see a test pattern, when you plug it to a screen or tv?

[vgdiy]

No test pattern on the screen.

[marqs]

It sounds like JTAG cnnection to FPGA works and you can write flash, but on power-up FPGA cannot load the firmware. Did you have “verify” enabled while programming .jic, and did it report success? If that went fine, I’d next check that MSEL pins are connected correctly.

[vgdiy]

the verify option was selected and the firmware reported success on completion. Ill take a look at the MSEL pins tomorrow.

[marqs]

Another thing to check is that FPGA properly gets 27MHz clock from the oscillator.

[vgdiy]

I just looked at pictures of my boards. the oscillator dot is not where the squared pin hole is. I have a feeling that is my problem. I will confirm tonight.

[vgdiy]

sorry for the delayed response, but fixing the oscillator fixed my problem.

[Ideal1st]

Hello everyone. It looks like that I have exact same problem, though I didn’t build the OSSC 1.6, but bought one ready made. Used it for some time. The unit was kept plugged in all the time. PSU is 5v 1.5a. Yesterday I tried to play some PS1 but got no image from OSSC though HDMI signal was detected by TV. I have power cycled the OSSC and it didn’t turn on anymore. LCD backlight flashes once being blank, red led blinks once and then green led is solid.

How can I troubleshoot?

[Morpheus_79]

You can check if the FPGA is working via JTAG connector and usb blaster. Since the problem sounds very similar to the one from the op you could check the oscillator via oscilloscope.

[Ideal1st]

I went for getting me a blaster to start with. After an attempt to reflash I will go looking for oscilloscope. How come the oscillator can become faulty after proving to be fully operational for some time?

[Morpheus_79]

Maybe it’s just a cold solder joint… maybe it’s a quality issue with the component.

But the assumption in this case is NOT: the oscillator is broken. It’s more or less: the FPGA doesn’t do anything – why is that? Could be a broken FPGA, or a broken oscillator,  or a broken flash, or a broken something else. Sometimes things simply break without an obvious reason.

 

[Ideal1st]

Well, I got my hands on the usb blaster and flashed the 0.90 to the OSSC

The thing didn’t boot up, so I tried reflashing. On my third attempt I got it booted up fine. I exhaled relaxed BUT!!! when I returned the thing to my TV rerouted all the cables it catched the same symptoms again. Screen blink then solid green…

Any ideas?

UPD: Back to the workbench I hooked the JTAG, powered on, got familiar “screen flash then solid green” and after around 30 seconds of standby powered on OSSC booted up! But eventually hanged… Now I am confused.

UPD2: Sometimes verification fails sometimes not:
Info (209060): Started Programmer operation at Fri Nov 1 22:29:51 2024
Info (209016): Configuring device index 1
Info (209017): Device 1 contains JTAG ID code 0x020F20DD
Info (209007): Configuration succeeded — 1 device(s) configured
Info (19845): Start Serial Flash Loader programming
Info (209018): Device 1 silicon ID is 0x14
Info (209044): Erasing ASP configuration device(s)
Info (209023): Programming device(s)
Info (209021): Performing CRC verification on device(s)
Error (209027): Verification failed for device number 1
Info (19845): End Serial Flash Loader programming
Error (209012): Operation failed
Info (209061): Ended Programmer operation at Fri Nov 1 22:30:29 2024

• This reply was modified 5 days, 16 hours ago by Ideal1st.
• This reply was modified 5 days, 15 hours ago by Ideal1st.
• This reply was modified 5 days, 15 hours ago by Ideal1st.
• This reply was modified 5 days, 15 hours ago by Ideal1st.
• This reply was modified 5 days, 15 hours ago by Ideal1st.

[Morpheus_79]

Sadly those inconsistent faults are the hardest to find. Have you checked the oscillator?

[Ideal1st]

I will take it to work tomorrow, they have an oscilloscope. (I never had experience with it) Shall I check if the oscillator outputs the required frequency?

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