PCB for Video / Keyboard controller by Grant Searle

[Thomas Riesen]

Hi all

I tried to design a PCB for Grant Searle's Monitor and Keyboard controller. But unfortunately

the system doesn't work. I checked the schematic several times, but I didn't found the error.

Is there anyone who is willing to help me? I would send the PCB to a test person for free.

http://searle.hostei.com/grant/MonitorKeyboard/index.html

Regards

Thomas

[Scott Lawrence]

I'll gladly help out. I've wanted one of these for a long time now.  

What's the symptoms you're seeing?  are you getting any video at all?

-s

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Scott Lawrence
yor...@gmail.com

[Steve Baines]

Hi, 

I successfully built one of these recently on strip board, and it's working fine.

I'd be happy to try to help.

   Cheers - Steve

[Peter Fielden-Weston]

Thomas,

I cannot help at the moment as my RC2014 is all broked and sad and lonely.

However, I have just had a look at your schematic and would like to raise a couple of questions.
1) Why are you using a MAX232? You have the two Atmel devices that Grant uses.

2) On the MAX232 why are you using T2IN as an RTS? Looking at the datasheet for the MAX232, it doesn't use RTS/DTR or any other flow control feature.

Sorry to be a PITA, :)

Peter

[Spencer Owen]

Just a suggestion, but as it's designed to be built on two breadboards and there's not too many components, why not try that. Build it from your schematic, not Grants to make sure you've got that part right.  If it works, then jumper across to just the keyboard part of your PCB then just the video part. 

Spencer 

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[Steve Baines]

As Peter said, you don't need the MAX232 to talk to the RC2014.  Since you are having problems it would be better to remove it (at least for now) so that there is less to debug.  Just use the TTL level serial connection.

Also, are you confident that you have burned the ATMEGAs correctly?  As well as flashing the code, they also need their fuses setting, and they need different fuse settings to each other.

Also, are you certain you didn't get them swapped over when you assembled it? :-)

Oh yeah, a couple of other things I remember from my build:

1. With Grants circuit the video level was low - I had to turn the brightness up pretty high to get a good picture.

2. It is sensitive to having a good power supply. If the voltage is a bit low then it stops working properly, so make sure you've got a solid supply.

[Thomas Riesen]

Hi all

Thank you for your suggestions!

Normally I am used to "burn" ATmega's and I am familiar with the fuses. The fuses are burned like on

Grant Searles page mentioned:

For the 328P interface chip:

 Low: 0xFF
High: 0xD9
Extended: 0xFF

The 328P display chip must be set to rail-to-rail crystal operation, so the fuse bytes for that would be:
Low: 0xF7 (ie. CKSEL3 = 0)
High: 0xD9
Extended: 0xFF

And I know, for using with RC2014 it's not necessary to convert the RX/TX to RS232 level, but I would

like to use this circuit also with my other SBC boards, they provide RS232 connections.

I am going to check the voltage, but I use a "Laboratory power supply ...

In my opinion the RST could be the problem, the pin is tied to VCC, no R/C circuit to reset the MCU.

I had no time to make further tests with an other program oder RST circuit ..... :-(

So, that's why I am helpless ,,,, Is anybody willing to test my pcb? Please send me your address

by PN.

Regards

Thomas

[Peter Fielden-Weston]

Thomas,

I've started lookinh at your schematic. First thing, the PS2 port, you have -

Pin
1) GND
2) CLK - Pulled up to VCC
3) NC
4) KB Data - Pulled up to VCC
5) NC
6) VCC

The PS2 spec for the PS2 connector shows -

Pin
1) Data
2) NC - Reserved
3) GND
4) 5v - VCC
5) CLK
6) NC - Reserved

So, that isn't going to help. :(

Peter

[Guido Santer]

Hi all,

as i also aim on doing the grant searle way of using my rc2014 i am curious on how the board development ended? Is there a usable Board anywhere available?

Best Regards

Guido

[Phil G]

I've used Grants video terminal many times in various projects, full builds and partial, every aspect of it,

the PS2, USB, video, BRG, composite or VGA - everything works perfectly.

Mine are mostly on veroboard, just one project uses a PCB I bought from Tindie some years ago.
In fact I made another, only last week, this time a simple 2400 serial display for a KO2019 with my usual modified chatpad:

If you've checked your build over & over I'd suggest maybe the PIC itself might be the problem - the PIC32MX250 can 

be a tad awkward to program - I made a simple adapter:
Cheers

Phil_G

https://philg.uk

[Phil G]

Phil_G>> I've used Grants video terminal many times

Sorry, brainfart,  I've used GEOFF's video terminal many times...