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Re: [Lcd4linux-devel] display on WRAP-Board - how fast is i2c? ho w good is the lpc connector?
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From: Luis.F.Correia <Lui...@se...> - 2006-07-25 13:28:01
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Hi!
> -----Original Message-----
> From: Stefan Krister [mailto:ste...@cr...]
> Sent: Tuesday, July 25, 2006 12:36 PM
> To: lcd...@li...
> Subject: Re: [Lcd4linux-devel] display on WRAP-Board - how
> fast is i2c? ho w good is the lpc connector?
>
> Hi Luis,
>
> Luis.F.Correia schrieb am 25.07.2006 11:47:
> >
> > They are needed to pull up the I2C lines at 3.3V, this is a
> > requirement from the I2C specifications.
>
> o.k. - for the rest of the readers - I provide your
> schematics as ascii:
For the sake of completeness, here's an update to the schematics:
The PCF is powered by +5V, but the I2C inputs are biased to
+3.3v, which is the correct voltage level of the WRAP board.
VCC +5V
+ 3.3v | .------------. .------------.
'----o---o .-|16 1|--. | |
| | | PCF8574 | | | LCD |
.-. .-. | 2|--o | |
| | | | | | | | |
| | | | | 3|--o | |
'-' '-' | | | | |
| | | | === | |
| | | | GND | |
SDA o-o---)---|15 | | |
| | 4|-----|D4 |
SCL o-----o---|14 | | |
| 5|-----|D5 |
.------------|8 | | |
| | 6|-----|D6 |
=== | | | |
GND | 7|-----|D7 |
| | | |
| 10 9 | | RS E RW |
'------------' '------------'
| | | | |
| '---------' | ===
'-----------------' GND
(Michael, you can add this to the wiki, if you like)
> >> I wired my display like yours. I configured lcd4linux as
> >>
> >> Display DOG-16x3 {
> >> Driver 'HD44780'
> >> Model 'generic'
> >> Bus 'i2c'
> >> Device '64'
>
> is that correct? It's the address of the chip?
I can't recall if we used decimal or hex notation in the config
definition. It does depend whether you are using the PCF8574 or
the PCF8574A, since they have different port addresses.
IIRC, mine is at hex:71, dec:112.
> That's wrong! It should be
>
> Wire {
> RW 'GND'
> RS 'DB4'
> ENABLE 'DB5'
> }
>
> Isn't it?
Yes, this is correct.
>
> > you'll need to add the specific /dev entries.
>
> Be free to provide me wiht your major/minor numbers. My
> devices are currently
>
> ls -al /dev/i2*
> crw-r--r-- 1 root root 89, 0 Jul 25 13:06 /dev/i2c-0
> crw-r--r-- 1 root root 89, 1 Jul 25 13:06 /dev/i2c-1
>
> > In WRAP, the temp sensor sits on bus 1, while the external
> bus is bus
> > 0. You are getting different results because you are using the in
> > kernel I2C drivers. The WRAP board uses the 'worng' values
> for the I2C
> > AccessBus controllers. Please check in the driver I
> previously sent to
> > get the proper I/O ports. You may have to patch the I2C driver to
> > match this board (scx200_acb i mean).
>
> Don't know what you want me to do ... Sure I'm using the
> in-kernel i2c driver. It works fine. I do not want to make
> changes in the kernel modules.
Well, i can't help much, as LEAF currently uses a 2.4 series kernel and we
do provide the accessbus driver.
> > With lcd4linux, you will only need the i2c-core, i2c-dev,
> i2c-proc and
> > the access bud driver.
> >
> > Nothing else is needed, because we do RAW chip access.
>
> Do the already loadesd modules affect lcd4linux?
If pcf8574 must _not_ be loaded. If it is, then lcd4linux will not work.
>
> > Can you post the dmesg messages?
>
> No, there is no dmesg in fli4l - but I have a full bootlog -
> what do you expect to see?
The messages around loading the i2c bus including the scx200_acb.
> MfG
>
> Stefan
Luis
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