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Forum: ARM programming with GCC/GNU tools Problem whit At91sam7s64 and lcd


Author: Daniel Gomez (danielgomezco)
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Hello I have a little problen I traind to do a little program but i have
a very rare problem i use a 16x2 LCD.

the problem is when it put energy in the procesador the  Lcd traid to
inizialiset but start in black but if i disconect the lcd and later
reconect and reset de  the chip it's start work correcty and inizialiset
de lcd correcty, why??????, i need the program start correcety when i
put de energy

i attach the main.c

Author: Martin Thomas (mthomas) (Moderator)
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Daniel Gomez wrote:
> Hello I have a little problen I traind to do a little program but i have
> a very rare problem i use a 16x2 LCD.
>
> the problem is when it put energy in the procesador the  Lcd traid to
> inizialiset but start in black but if i disconect the lcd and later
> reconect and reset de  the chip it's start work correcty and inizialiset
> de lcd correcty, why??????,
By "start in black" you mean 1 or 2 solid black lines? What happens if
you just reset the controller without "disconnect/reconnect" of the
LCD-module?

> i need the program start correcety when i
> put de energy
Usual problems causing LCD startup-problems and unreliable startup:
- some LCD-modules need some "startup-time" to stablize the internal
supplies (i.e. contrast-voltage boosters, segment-controller(s))
- the delay-times esp during init are too short (check with a scope)
- configuration of the used IO-Pins (check PIO-config, -clocking,
alternate pin-functions, check with scope)
- initial state of some pins not defined correctly esp. before the init
sequence
(write a minimal application which just toogles the pins against
pull-up/pull-down-resistors)
- logic levels are not fully compatible (compare minimum voltage for
input logic high from module's datasheet and output voltage for µC).
- signals are not "clean" (check with a scope)
- "Enable-strobe-time" short (again, check with a scope)
- LCD-module just broken, did you try with another one.

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