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Volhout
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Joined: 05/03/2018
Location: Netherlands
Posts: 5089

Posted: 07:58am 17 Oct 2018

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I hand wired an LCD backpack PCB (1455 and MX170 and LCD) and it works fine (after I found a soldering short with help of the white wizard) on the companies i5 laptop.

I plug this board in a older Celeron laptop (my own) it has startup problems.
I looked into this forum and read about 100mA current limit, so I decided to remove the actual LCD (backlight current) so the board would consume less than 50mA.

But the effect remains. The board works on the i5 (checked all 3 USB ports) and does not work on the Celeron (checked all 4 USB ports).

Does not work means: no welcome message, and if you type a character the LED on the 1455 blinks 2x (for 2 characters) and then stops. So it accepts 2 characters, then stops. Autorun is not active, it is virgin.

I replaced the 1455 (the one I programmed myself) by a 1455 bought pre-programmed. Effect remains. I could not replace the MX170 since I only have one.

I bought a official red LCD Backpack PCB, and stuffed it. This board has exactly the same effect. This is an official LCD backpack config as advestised on Geoff's website. With or without actual LCD, the board refuses to work on the Celeron Laptop.

The celeron laptop however works with arduino boards (UNO / MEGA) reliable.

I fail to understand why the celeron won't work with the micromite. I though it might relate to rise time of 5V when plugging in the board (power on reset critical) but have not been able to get an oscilloscope to look at it.

Has anyone made observations like these, boards that simply refuse to work on certain computers?

Volhout

PicomiteVGA PETSCII ROBOTS

Geoffg

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Joined: 06/06/2011
Location: Australia
Posts: 3292

Posted: 11:03am 17 Oct 2018

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My guess is that it is the device driver on the older PC causing the trouble. The latest drivers are here: http://geoffg.net/microbridge.html#Downloads

Another issue might be the version of Windows, from memory the driver supports Win 7 or later.

Geoff Graham - http://geoffg.net

Azure

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Joined: 09/11/2017
Location: Australia
Posts: 446

Posted: 03:55am 18 Oct 2018

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You can also try and isolate it to the drivers/USB port or something else by looping the Tx/Rx pins going from the 1455 to the MX170.

That way everything you type should echo back if the USB interface and drivers are working.

If you can easily remove power to the MX170 on your board (or remove the MX170 if it is socketed) then with no LCD you will only be driving the 1455 so power will be in the low mA.

Volhout
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Joined: 05/03/2018
Location: Netherlands
Posts: 5089

Posted: 07:01am 18 Oct 2018

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All,

Thanks for your help.
I can confirm it was in the driver.

Thanks Geoff

PicomiteVGA PETSCII ROBOTS

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