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subalib
Newbie

Joined: 07/02/2019
Location: Australia
Posts: 11

Posted: 10:07am 08 Feb 2019

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Hi I'm a newbie currently trying to develop an understanding of MMBASIC on a Micromite Plus 100. It is all working well but for the life of me I can't display a BMP image on the LCD. I am using Tera Term as a serial console and everything is being mirrored to the LCD. As a learning exercise I have downloaded Geoff's Tiger pic and copied it to the SD card. Using the command LOAD IMAGE "tiger.bmp" on hitting return the LCD screen clears to black but the image does not load. I have to do a reset for it to start working again.
I have also noticed that the text echoed on the LCD is often gobbledegook although when it displays the output of a command such as OPTION LIST the text is perfect.
Any assistance would be appreciated. Thanks.

TassyJim

Guru

Joined: 07/08/2011
Location: Australia
Posts: 6283

Posted: 08:41pm 08 Feb 2019

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Hi and welcome.

What display are you using?
There are differences between suppliers which means you might have to try different options.
The 5 and 7 inch SSD1963 each have two choices. eg: SSD1963_7 and SSD1963_7A
If that is the display you have, try both options.

A copy of your OPTION LIST would be helpful.

Jim

VK7JH
MMedit

Grogster

Admin Group

Joined: 31/12/2012
Location: New Zealand
Posts: 9610

Posted: 10:20pm 08 Feb 2019

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Hi.

As an experiment, slow the CPU speed to 40MHz at the Tera-Term console with the command CPU 40, and then see if your problems go away.

[Quote=MicroMite Plus manual, page 15]
Generally 7 inch and larger displays have a separate pin on the connector (marked 5V) for powering the backlight from a 5V supply. If this pin is not provided the backlight power will be drawn from the 3.3V pin. Note that the power drawn by the backlight can be considerable. For example, a 7 inch display will typically draw 330 mA from the 5V pin. The current drawn by the backlight can cause a voltage drop on the LCD display panel�s ground pin which can in turn shift the logic levels as seen by the display controller resulting in corrupted colours or text. An easy way of diagnosing this effect is to reduce the CPU speed to (say) 40MHz. If this fixes the problem it is a strong indication that this is the cause. Soldering power and ground wires direct to the LCD display panel�s PCB is one workaround.

Edited by Grogster 2019-02-10

Smoke makes things work. When the smoke gets out, it stops!

subalib
Newbie

Joined: 07/02/2019
Location: Australia
Posts: 11

Posted: 11:58pm 08 Feb 2019

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Thank you to you both for the prompt replies. I switched it on this morning to print the options list and tried loading an image and it worked. However, a minute or two later it reverted to previous behaviour. I wondered whether it was a heat related or power supply issue so reduced the backlight from 100% to 50% and it seemed better. I then saw Grogsters post and reduced the CPU speed to 40% which fixed the problem completely. My display is 5" not 7" but seems to have similar issues. I thought I had read the manual pretty thoroughly but clearly not

. Thanks again. I will enjoy getting more familiar with MMBASIC and this forum will be a mine of information.

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