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Vampire05
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Joined: 06/12/2020
Location: Germany
Posts: 88

Posted: 10:25am 16 Dec 2020

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Hi guys,

i need your ideas. I can not get a video signal out from my ascii terminal (vt100 emulator):

Instead of the MCP1700-330 i used the Wemos ESP32 18650 Battery Shield.
For VGA, i only connected the green signal (Pin 2) and soldered the "green" pad in the "select color" section on the pcb. I have checked connection from PIC to VGA Output-> everytbhing is fine! I testet 3 VGA Monitors but no visible Output. Same on Composite Output!

If i turn the device on, the activity led is on. On every keypress of the ps2 Keyboard the led is blinking. So i think the input part works fine.

Any Ideas of whats going on with the Video Output?

The Schematic:

Geoffg

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Joined: 06/06/2011
Location: Australia
Posts: 3308

Posted: 11:48am 16 Dec 2020

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It does sound like the PIC32 is working correctly.

When you are testing the terminal make sure that you place a jumper across the Tx and Rx pins. That way anything you type will be echoed back and you can then see the result of your typing on the screen.

If that does not work you should try an oscilloscope on pin 12 of the PIC32. Do you see anything?

Geoff

Geoff Graham - http://geoffg.net

matherp
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Joined: 11/12/2012
Location: United Kingdom
Posts: 10590

Posted: 11:57am 16 Dec 2020

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Have you connected all of the grounds on the VGA output? (pins 5,6,7,8,and 10). For many monitors you need all of them

Vampire05
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Joined: 06/12/2020
Location: Germany
Posts: 88

Posted: 12:14pm 16 Dec 2020

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@matherp they seems to be already connected in the VGA socket. i have checked it with multimeter.

@Geoff

yes i connected RX with TX with the jumper cable on the frontpanel (second picture).

Pin 12 on the oscilloscope:

Edited 2020-12-16 22:14 by Vampire05

Vampire05
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Joined: 06/12/2020
Location: Germany
Posts: 88

Posted: 01:35pm 16 Dec 2020

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Here is Pin 12 with different oscilloscope timings:

Vampire05
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Joined: 06/12/2020
Location: Germany
Posts: 88

Posted: 02:22pm 16 Dec 2020

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VSync:

Hsync:

Green channel

Geoffg

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Joined: 06/06/2011
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Posted: 02:42pm 16 Dec 2020

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You have activity on all the required VGA signal lines and you can be sure that the firmware is generating the correct signals... so the fault must be in either:
- Your wiring to the VGA connector
- Your VGA cable
- Your monitor

You need to check all three VERY carefully.

Geoff

Geoff Graham - http://geoffg.net

gob33
Newbie

Joined: 26/02/2018
Location: France
Posts: 6

Posted: 02:44pm 16 Dec 2020

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You will go faster buying an AXEL AX3000 thin client terminal .

Vampire05
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Joined: 06/12/2020
Location: Germany
Posts: 88

Posted: 04:03pm 16 Dec 2020

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it works now! Thank you very much Geoff!

The Problem was a missing Connection between Pin 18 and Pin 25 on the self eached PCB. This is the reason why VGA AND Composite does not work. The HSYNC is used by both signals! Now both works.

Edited 2020-12-17 02:11 by Vampire05

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