exxos's Atari, Amiga & retro forum

Posted: **27 Feb 2026 18:22**

Hi !

I'm lost...
I have build a new Atari ST projet, V.1.1 of Atari ST ATX with a old STF working.
PCb is finished and 'working' (I can Start, demo, game, tools with gotek)
Video and Audio output work
BUT... no keyboard, no mouse

The problem is NOT the mouse and the keyboard, I'v tested a lot of
The problem is NOT the PIC16F with Eifel code
why I say that.

I can read/check PIC16F and tested another PIC I have, same issue
I mesured with scope the oscilation on the boatd, 2, 4mhz ... etc, all seems good.
I have also checked all chip and mostly 6850 (with anoter Atari AND Chip Tester Pro BlackBit)

If I take measure with my scope on Pin2 and Pin6 of one of 6850, I can read RX and TX signals
I can See on pin2 a signals, a 'key code' when I push a Key in my Keyboard (and Cap's lock / led working)
So..for me, PIC16F is well programmed and CIA receive code
BUT... I can see NOTHING on TX line
I have also verified 500Khz oscilation on 2 x 6850, they OK

For unknow reason, It's like the CIA don't activated the keybord
On boot I can see my 2 signals up to 5V
(see picture)
no variation on TX line, already stuck to High

I have also remove PIC, add a little PCB with 74LS244 and 2 EMI
to have a Full 'circuit' of real keyboard and connect so, a Real Atari Keyboard
2 leds of my Real Keyboard work, One PowerOn, One for floppy activity
But... not detected....worse, not initialised and so, when I push a key on this real Keyb, No activity on Pin2 (RX)

So... I'm pretty sure the keyboard is NOT itinitialised

If anybody have idea...
Thks a lot.

Last:Yep, post modified.

boot.jpg

Posted: **27 Feb 2026 21:05**

Can you please upload images to the forum and not link to external sites please as it is actually against forum policy. Thanks.

Furthermore, your image does not actually seem to load anything.

Posted: **28 Feb 2026 07:12**

Giants wrote: 27 Feb 2026 18:22 Hi !

I'm lost...
I have build a new Atari ST projet, V.1.1 of Atari ST ATX with a old STF working.
PCb is finished and 'working' (I can Start, demo, game, tools with gotek)
Video and Audio output work
BUT... no keyboard, no mouse

The problem is NOT the mouse and the keyboard, I'v tested a lot of
The problem is NOT the PIC16F with Eifel code
why I say that.

I can read/check PIC16F and tested another PIC I have, same issue
I mesured with scope the oscilation on the boatd, 2, 4mhz ... etc, all seems good.
I have also checked all chip and mostly 6850 (with anoter Atari AND Chip Tester Pro BlackBit)

If I take measure with my scope on Pin2 and Pin6 of one of 6850, I can read RX and TX signals
I can See on pin2 a signals, a 'key code' when I push a Key in my Keyboard (and Cap's lock / led working)
So..for me, PIC16F is well programmed and CIA receive code
BUT... I can see NOTHING on TX line
I have also verified 500Khz oscilation on 2 x 6850, they OK

For unknow reason, It's like the CIA don't activated the keybord
On boot I can see my 2 signals up to 5V
(see picture)
no variation on TX line, already stuck to High

I have also remove PIC, add a little PCB with 74LS244 and 2 EMI
to have a Full 'circuit' of real keyboard and connect so, a Real Atari Keyboard
2 leds of my Real Keyboard work, One PowerOn, One for floppy activity
But... not detected....worse, not initialised and so, when I push a key on this real Keyb, No activity on Pin2 (RX)

So... I'm pretty sure the keyboard is NOT itinitialised

If anybody have idea...
Thks a lot.

Last:Yep, post modified.

boot.jpg

Which PIC16F chip are you using? Please provide full code as there are various chips that start with PIC16F.

Posted: **28 Feb 2026 08:35**

Hi !

The initial project is here : https://ataripcb.pl/atari_st_atx_v1.1.html
It provide ONLY one file for IC10 (PIC16F876)
If we compare it to the original Effeil project file, it corresponds to the eiffel_i.hex file.

PCB.jpg

Here a capture to Real Atari ST, PIN2 of 6850 (so RX)
With the key 'E' pressed

ST_REAL_KEY_E.jpg

and on the ST ATX projet, same

ST_ATX_KEY_E.jpg

For me, same signal
Corresponding at 0x12

Posted: **28 Feb 2026 18:21**

Hummm.... interresting... IRQ (pin7) is going and stuck to 0V........
It's not normal because they are a PullUp on this line.

IC1 removed (this is the Keyboard controler CIA) : Same... signal stuck to 0V
Return IC1 in place and IC2 (other CIA) removed.
And... IRQ now it's normal, going and stay High

Boot on Floopy and test Keyboard and Mouse.
And..........it's working........ O_o'

It's really strange because it passed all the good with Chip Tester Pro blackBit
I will check with another CIA.

So... another CIA tested and, all are good but, when a second CIA is inserted, the IRQ line stuck to 0V
I have checked All lines on the PCB and component, focus on CIA
AND... when I remove the OK1 chipset (the 4N33 on schematic and H11 L2 3344 on my pcb) the IRQ line is good and all work good.
SO...........

2 options :
- H11 L2 3344 is NOT a 4N33
- my chipset is BAD

Posted: **28 Feb 2026 22:07**

Giants wrote: 28 Feb 2026 18:21 Hummm.... interresting... IRQ (pin7) is going and stuck to 0V........
It's not normal because they are a PullUp on this line.

IC1 removed (this is the Keyboard controler CIA) : Same... signal stuck to 0V
Return IC1 in place and IC2 (other CIA) removed.
And... IRQ now it's normal, going and stay High

Boot on Floopy and test Keyboard and Mouse.
And..........it's working........ O_o'

It's really strange because it passed all the good with Chip Tester Pro blackBit
I will check with another CIA.

So... another CIA tested and, all are good but, when a second CIA is inserted, the IRQ line stuck to 0V
I have checked All lines on the PCB and component, focus on CIA
AND... when I remove the OK1 chipset (the 4N33 on schematic and H11 L2 3344 on my pcb) the IRQ line is good and all work good.
SO...........

2 options :
- H11 L2 3344 is NOT a 4N33
- my chipset is BAD

I used 4N33, CNY17F-3 and CNY17F-4

OK1 is designed for a phototransistor optocoupler. The H11L2 is a logic‑gate optocoupler with different pinout, supply requirements, and behavior, so it is the wrong IC.

The H11L2 needs 5 V/GND, and those pins do not exist on the OK1 footprint, so it cannot operate and may be damaged.

Posted: **01 Mar 2026 07:35**

Yes, I saw that last night when I was looking at the datasheets.

In fact, with this type of failure, we first look for incorrect programming of the PIC or its oscillation, or even a CIA problem.
We don't necessarily think of a problem that interferes with the dialogue on the CIA.

In addition, there is nothing special on the thermal camera and it is quite difficult to read the reference on the OK1.

On the other hand, the oscilloscope is telling.
The second CIA is not responding correctly.
And since there aren't 150 signals on it, we quickly find the OK1.
I'm not at all used to repairing Atari computers; I repair Amiga computers more, so this is a nice new adventure for me :)
In any case, thank you for your feedback and yo

Posted: **17 Apr 2026 09:24**

Ok, solved.
Wrong chipset 'H11 L2 3344'
This chips 'freeze' CIA and don't The couple of CIA work well.
Chip changed and now work good.

Next issue :)

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