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PICList Thread
'I2C. and VFD'
1998\02\25@063723 by Keith Howell

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Steve Parker <spam_OUTSteve.ParkerTakeThisOuTspamSRC.BAE.CO.UK>

> Hi,
> I have spent a torrid weekend trying to get my 16C74 communicating
> with a 24LC16B I2C memory chip.

You sad man! Just _how_ torrid are we talking here? ;-)

My weekend was spent trying to get my PC reliably initialising a 2x20 char
VFD (much like you LCD I expect).

> I have based my efforts on AN578,

I started from there. It's crap.

> but this uses a multi-master environment that is controlled through
> interrupts. I have therefore removed all the interrupt and keyboard
> stuff and just use the RDBYTE and WRBYTE routines. It appears to
> write ok but the values read back seem to be garbage.

Been there, done that. Symptoms caused by not NACKing the final byte
read from the chip. STOP then START does not reset everything inside.

> 1) Is there any point using the I2C features on the 16C74 for my app?

If you're the only master, then you can bit bang master behaviour.
You won't need the I2C hardware, which is for implementing slave behaviour.

> 2) Do I need interrupts.

No. This is only needed when some other I2C master device talks to your PIC

> 3) Is there a better example (code etc) anywhere which shows me more clearly.
> I expect you've had similar questions to these before - sorry!!

> PS: the application is storing altitude values in a model rocket.

I'm interested in that too, but have no time at the moment.

Steen Jensen wrote:

>
> Have a look at AN567. The code is very simple and easy to use.
>

I've given up on Microchip app notes.
You can't assume they work. They have bugs in.

If anybody wants it, I can e-mail them a 250K wordperfect file
of all the relevant e-mail postings I on the subject.


Meanwhile, has anyone got any rock-solid code for initialising the
Noritake Itron CU20025ECPB-U1J vacuum florescent display module?
My PIC seems to be doing it okay, but my printer-port bit-banging
software is not. I thought it might be cable noise, but once it
is initialised the chars don't seem to produce errors.

The module interface resembles the popular HD44780 LCD interface,
and certain web pages mention instruction times (which my PIC
does not include, without any ill effects).

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