Problem with OLED and Gotek

HxC Floppy Emulator on Amiga support
Post Reply
tytan
Posts: 4
Joined: Tue Jan 09, 2018 10:01 pm

Re: Problem with OLED and Gotek

Post by tytan » Tue Jan 09, 2018 11:47 pm

Hello.
I have Gotek with HxC.
I have connected the same OLED as in this post. At the beginning, OLED did not light up.
After setting the start delay to 5, works well! (HXCFEUSB_V3_1_1_0a.UPD)
Thank you, good job,
tytan

Jeff
Site Admin
Posts: 5074
Joined: Fri Oct 20, 2006 12:12 am
Location: Paris
Contact:

Re: Problem with OLED and Gotek

Post by Jeff » Wed Jan 10, 2018 1:27 am

tytan wrote:
Tue Jan 09, 2018 11:47 pm
Hello.
I have Gotek with HxC.
I have connected the same OLED as in this post. At the beginning, OLED did not light up.
After setting the start delay to 5, works well! (HXCFEUSB_V3_1_1_0a.UPD)
Thank you, good job,
tytan
Well i would prefer to avoid this option... Will received one of these screen this week. Hope to understand why they are working so bad...
(PS : Same issue there : http://torlus.com/floppy/forum/viewtopi ... =33&t=3258)

tytan
Posts: 4
Joined: Tue Jan 09, 2018 10:01 pm

Re: Problem with OLED and Gotek

Post by tytan » Wed Jan 10, 2018 6:51 pm

Measurement showed that this OLED does not have a pull up.
Does an ohmmeter: between + and SDA or SCL should show values around a few Kohms?
tytan

Jeff
Site Admin
Posts: 5074
Joined: Fri Oct 20, 2006 12:12 am
Location: Paris
Contact:

Re: Problem with OLED and Gotek

Post by Jeff » Wed Jan 10, 2018 10:34 pm

tytan wrote:
Wed Jan 10, 2018 6:51 pm
Measurement showed that this OLED does not have a pull up.
Does an ohmmeter: between + and SDA or SCL should show values around a few Kohms?
tytan
I think that there is a LDO voltage regulator. To measure the pull up you must use the output pin of this LDO.

tytan
Posts: 4
Joined: Tue Jan 09, 2018 10:01 pm

Re: Problem with OLED and Gotek

Post by tytan » Sat Jan 13, 2018 8:48 pm

You're right.
There is 662K.
I have measured - they are pull up.

I use a few days with a delay of 5, OLED works correctly - always starts.

Jeff
Site Admin
Posts: 5074
Joined: Fri Oct 20, 2006 12:12 am
Location: Paris
Contact:

Re: Problem with OLED and Gotek

Post by Jeff » Sat Jan 13, 2018 9:37 pm

tytan wrote:
Sat Jan 13, 2018 8:48 pm
You're right.
There is 662K.
I have measured - they are pull up.

I use a few days with a delay of 5, OLED works correctly - always starts.
662K ? Very high value for pull-up...

btw i have just have received one of these screen. i will try to check this tomorrow.

tytan
Posts: 4
Joined: Tue Jan 09, 2018 10:01 pm

Re: Problem with OLED and Gotek

Post by tytan » Sat Jan 13, 2018 10:02 pm

662K it's stabilizer ;) https://www.mysensors.org/uploads/57c1a ... e/662K.png
pull ups 4.7k ohm

Jeff
Site Admin
Posts: 5074
Joined: Fri Oct 20, 2006 12:12 am
Location: Paris
Contact:

Re: Problem with OLED and Gotek

Post by Jeff » Sun Jan 14, 2018 2:57 pm

So i got time to have a closer look to this problem :

As expected the problem is the reset RC circuit. This screen have some curious RC part value which make the oled controller staying in reset a during a looonnnng time after the power up. The Reset RC circuit is done with C8 (4.7uF) & R3 (560K !!!!). Which give a time constant of 2.632 seconds. So no surprise here...

I have changed the resistor value to reduce a lot this time constant. ~4.7K ohms value seems to work reliably without any extra software delay :

First try :
diymorecc_patch1.jpg
diymorecc_patch1.jpg (63.4 KiB) Viewed 98 times
diymorecc_patch2.jpg
diymorecc_patch2.jpg (81.17 KiB) Viewed 98 times
The Fix :
oled_diymorecc_fix.jpg
oled_diymorecc_fix.jpg (208 KiB) Viewed 98 times

Jeff
Site Admin
Posts: 5074
Joined: Fri Oct 20, 2006 12:12 am
Location: Paris
Contact:

Re: Problem with OLED and Gotek

Post by Jeff » Sun Jan 21, 2018 12:13 pm

One more thing about these oled screens : it seems that they prefer to be powered with 5V instead of 3.3V : No more brightness variation and brighter display.

Post Reply