GPIO on consoleLCD-VX

[Arigead]

Hello all,
    I got the LCD gum pack a while back and have been happily
playing about with it and picking up bits of info from this list. I
am however at a loss trying to work out how you interface to the
GPIO on the console LCD-vx.

I'm not sure what I want to do but it's a learning experience so
if I could even connect a LED to the system and light it that
would be a start. Ideally I'd like to connect a temperature sensor
but perhaps I should forget the A/D stuff until I can light a led
and maybe "read" a switch state.

This is a seriously basic question. I'm sorry I know this but I've
been searching and can't find any info. Maybe what I expected
is in error. I had expected as the consoleLCD-vx expansion has
GPIO listed in it's features I'd assumed that there'd be solder
points.

If anybody could point me in the correct direction I'd be very
grateful

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[Dave Hylands]

Hi,

>     I got the LCD gum pack a while back and have been happily
> playing about with it and picking up bits of info from this list. I
> am however at a loss trying to work out how you interface to the
> GPIO on the console LCD-vx.
>
> I'm not sure what I want to do but it's a learning experience so
> if I could even connect a LED to the system and light it that
> would be a start. Ideally I'd like to connect a temperature sensor
> but perhaps I should forget the A/D stuff until I can light a led
> and maybe "read" a switch state.
>
> This is a seriously basic question. I'm sorry I know this but I've
> been searching and can't find any info. Maybe what I expected
> is in error. I had expected as the consoleLCD-vx expansion has
> GPIO listed in it's features I'd assumed that there'd be solder
> points.

So, pretty much every pin can be configured for some purpose or GPIO.
So you need to find some pin whose functionality you're not using, and
use it as a GPIO pin.

Some likely candidates on the consoleLCD-vx are the audio (or AC97
pins), and possibly the NSSP (SPI) pins.
The AC97 pins are X_BIT_CLK, SDATA_IN, CLK32, SDATA_OUT, NACRESET,
SYNC. The NSSP (SPI) pins are: X_MOSI, X_MISO, NSSPFRAME, and NSSPCLK.

GPIO28 - X_BIT_CLK
GPIO29 - SDATA_IN
GPIO09 - CLK32
GPIO30 - SDATA_OUT
GPIO113 - NACRESET
GPIO31 - SYNC
GPIO13 - X_MOSI
GPIO11 - X_MISO
GPIO14 - NSSPFRAME
GPIO19 - NSSPCLK

I grabbed those from the consoleLCD-vx schematics. You can also find
them on the motherboard I/O page.

If you do:

modprobe proc_gpio
echo "GPIO out set" > /proc/gpio/GPIO31 will drive the SYNC line at 3.3v
echo "GPIO out clear" > /proc/gpio/GPIO31 will drive the SYNC line to ground.

So if you had an LED & current limiting resistor connected, one way
would light it, and one way would extinguish it (which way does what
depends on the exact wiring).

Similarly, for input, you'd connect a pullup resistor between say
CLK32 and 3.3v, and then connect a switch between CLK32 and ground.
With the switch open:
echo "GPIO in" > /proc/gpio/GPIO9 will configure CLK32 as a GPIO pin.
cat /proc/gpio/GPIO9 will then show you whether the pin is set (3.3v)
or clear (0v).

--
Dave Hylands
Vancouver, BC, Canada
http://www.DaveHylands.com/

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[Arigead]

On Jan 8, 2008 3:03 PM, Dave Hylands <dhylands@...> wrote:

> Hi,
>
>
> >     I got the LCD gum pack a while back and have been happily
> > playing about with it and picking up bits of info from this list. I
> > am however at a loss trying to work out how you interface to the
> > GPIO on the console LCD-vx.
> >
> > I'm not sure what I want to do but it's a learning experience so
> > if I could even connect a LED to the system and light it that
> > would be a start. Ideally I'd like to connect a temperature sensor
> > but perhaps I should forget the A/D stuff until I can light a led
> > and maybe "read" a switch state.
> >
> > This is a seriously basic question. I'm sorry I know this but I've
> > been searching and can't find any info. Maybe what I expected
> > is in error. I had expected as the consoleLCD-vx expansion has
> > GPIO listed in it's features I'd assumed that there'd be solder
> > points.
>
> So, pretty much every pin can be configured for some purpose or GPIO.
> So you need to find some pin whose functionality you're not using, and
> use it as a GPIO pin.
>
> Some likely candidates on the consoleLCD-vx are the audio (or AC97
> pins), and possibly the NSSP (SPI) pins.
> The AC97 pins are X_BIT_CLK, SDATA_IN, CLK32, SDATA_OUT, NACRESET,
> SYNC. The NSSP (SPI) pins are: X_MOSI, X_MISO, NSSPFRAME, and NSSPCLK.
>
> GPIO28 - X_BIT_CLK
> GPIO29 - SDATA_IN
> GPIO09 - CLK32
> GPIO30 - SDATA_OUT
> GPIO113 - NACRESET
> GPIO31 - SYNC
> GPIO13 - X_MOSI
> GPIO11 - X_MISO
> GPIO14 - NSSPFRAME
> GPIO19 - NSSPCLK
>
> I grabbed those from the consoleLCD-vx schematics. You can also find
> them on the motherboard I/O page.
>
> If you do:
>
> modprobe proc_gpio
> echo "GPIO out set" > /proc/gpio/GPIO31 will drive the SYNC line at 3.3v
> echo "GPIO out clear" > /proc/gpio/GPIO31 will drive the SYNC line to ground.
>
> So if you had an LED & current limiting resistor connected, one way
> would light it, and one way would extinguish it (which way does what
> depends on the exact wiring).
>
> Similarly, for input, you'd connect a pullup resistor between say
> CLK32 and 3.3v, and then connect a switch between CLK32 and ground.
> With the switch open:
> echo "GPIO in" > /proc/gpio/GPIO9 will configure CLK32 as a GPIO pin.
> cat /proc/gpio/GPIO9 will then show you whether the pin is set (3.3v)
> or clear (0v).
>
> --
> Dave Hylands
> Vancouver, BC, Canada
> http://www.DaveHylands.com/
>

Oh my God!

Thanks a million Dave,
    and as for my reaction to it I didn't think I'd have to start
looking at schematics
Oh well. ;-)

There are a few points that I could soler to on the ConsoleLCD-vx
which have labels on.
I'll go and dig out the schematics and see which I can get to that is
not used. There's

AC9
NSSP
A2D
I2C
BTUART
STUART
FFUART

on the board so perhaps I could use some of them. Most of those names
don't strike me
as being useful for lighting my first Led. Unless I do it of a serial port

Thanks again for responding to my question and I'm now off to look at
loads of lines on
schematics ;-)

John Whitmore

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[Dave Hylands]

Hi John,

> Oh my God!
>
> Thanks a million Dave,
>     and as for my reaction to it I didn't think I'd have to start
> looking at schematics
> Oh well. ;-)

The reason to look at the schematics is to figure out the signal names
that actually come out the connectors. For many things, looking at
this page will suffice:
<http://docswiki.gumstix.com/Verdex_60pin_connector_chart>

But you won't find X_MOSI there. Instead, you'll find SSPTXD2.

So that's the reason I go to the schematics.

> There are a few points that I could soler to on the ConsoleLCD-vx
> which have labels on.
> I'll go and dig out the schematics and see which I can get to that is
> not used. There's
>
> AC9

This is really AC97 - for the audio subsystem.

> NSSP

Also known as SPI.

> A2D

These lines come from the touch screen controller found on the
consoleLCD-vx board and not directly form the gumstix.

> I2C

On the verdex, these can be used as GPIO. On the connex they can't.
i2c is used to talk to the touchscreen controller, so you might not
get what you expect if you try to use these as GPIO.

> BTUART
> STUART
> FFUART

These are the 3 serial ports. Using these lines as GPIO would require
removing some resistors on the board, since the logic-level to
RS-232-level voltage converters will be driving some of the lines.

> on the board so perhaps I could use some of them. Most of those names
> don't strike me
> as being useful for lighting my first Led. Unless I do it of a serial port

I'd probably go the AC97 stuff.

--
Dave Hylands
Vancouver, BC, Canada
http://www.DaveHylands.com/

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[Edward Y]

Hi Dave,


I can light a LED which is connected to GPIO13 (X_MOST) and the GND right above it.

The LED blinks when I do echo "GPIO out set" > /proc/gpio/GPIO13.

Is blinking the right behavior for my LED?

I'm would like to attach a buzzer and a LED so that they function as status indicators for my gumstix.

Do you have any suggestion?


Thanks
Edward

Dave Hylands wrote:

Hi,

>     I got the LCD gum pack a while back and have been happily
> playing about with it and picking up bits of info from this list. I
> am however at a loss trying to work out how you interface to the
> GPIO on the console LCD-vx.
>
> I'm not sure what I want to do but it's a learning experience so
> if I could even connect a LED to the system and light it that
> would be a start. Ideally I'd like to connect a temperature sensor
> but perhaps I should forget the A/D stuff until I can light a led
> and maybe "read" a switch state.
>
> This is a seriously basic question. I'm sorry I know this but I've
> been searching and can't find any info. Maybe what I expected
> is in error. I had expected as the consoleLCD-vx expansion has
> GPIO listed in it's features I'd assumed that there'd be solder
> points.

So, pretty much every pin can be configured for some purpose or GPIO.
So you need to find some pin whose functionality you're not using, and
use it as a GPIO pin.

Some likely candidates on the consoleLCD-vx are the audio (or AC97
pins), and possibly the NSSP (SPI) pins.
The AC97 pins are X_BIT_CLK, SDATA_IN, CLK32, SDATA_OUT, NACRESET,
SYNC. The NSSP (SPI) pins are: X_MOSI, X_MISO, NSSPFRAME, and NSSPCLK.

GPIO28 - X_BIT_CLK
GPIO29 - SDATA_IN
GPIO09 - CLK32
GPIO30 - SDATA_OUT
GPIO113 - NACRESET
GPIO31 - SYNC
GPIO13 - X_MOSI
GPIO11 - X_MISO
GPIO14 - NSSPFRAME
GPIO19 - NSSPCLK

I grabbed those from the consoleLCD-vx schematics. You can also find
them on the motherboard I/O page.

If you do:

modprobe proc_gpio
echo "GPIO out set" > /proc/gpio/GPIO31 will drive the SYNC line at 3.3v
echo "GPIO out clear" > /proc/gpio/GPIO31 will drive the SYNC line to ground.

So if you had an LED & current limiting resistor connected, one way
would light it, and one way would extinguish it (which way does what
depends on the exact wiring).

Similarly, for input, you'd connect a pullup resistor between say
CLK32 and 3.3v, and then connect a switch between CLK32 and ground.
With the switch open:
echo "GPIO in" > /proc/gpio/GPIO9 will configure CLK32 as a GPIO pin.
cat /proc/gpio/GPIO9 will then show you whether the pin is set (3.3v)
or clear (0v).

--
Dave Hylands
Vancouver, BC, Canada
http://www.DaveHylands.com/

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[Dave Hylands]

Hi Edward,

> I can light a LED which is connected to GPIO13 (X_MOST) and the GND right
> above it.
>
> The LED blinks when I do echo "GPIO out set" > /proc/gpio/GPIO13.
>
> Is blinking the right behavior for my LED?

No - the LED should go on solid. Hopefully you connected an LED and a
current limitnig resistor.

> I'm would like to attach a buzzer and a LED so that they function as status
> indicators for my gumstix.
>
> Do you have any suggestion?

I've never tried driving a buzzer, but presumably you could. You'd
need some type of driver circuitry.

There is a PWM output on the gumstix which might be usable. You'd need
to look at the frequency range that it can produce.

You Should be able to use an ordinary speaker with a simple circuit like this:
<http://www.sixca.com/micro/mcs51/music51/index.html>

You just need to provide a square wave on the P2.0 line with the
frequency you'd like to produce.

--
Dave Hylands
Vancouver, BC, Canada
http://www.DaveHylands.com/

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[Edward Y]

Hi Dave,


Oops, I didn't use a current-limiting resistor; I'll go get one.

The LED I got is labeled 'Can be driven directly with 3-12VDC', maybe it's got an integrated resistor but it looks very ordinary and small.

As for the buzzer, I didn't know I would need a driver circuit for the buzzer. I'll figure it out.

The buzzer I got is labeled, 'Operating Voltage: 3-8Vac', 'Frequency: 2400Hz'.

Also, on the example circuit what does P2.0 mean?


Thanks for your advises.
Edward

Dave Hylands wrote:

Hi Edward,

> I can light a LED which is connected to GPIO13 (X_MOST) and the GND right
> above it.
>
> The LED blinks when I do echo "GPIO out set" > /proc/gpio/GPIO13.
>
> Is blinking the right behavior for my LED?

No - the LED should go on solid. Hopefully you connected an LED and a
current limitnig resistor.

> I'm would like to attach a buzzer and a LED so that they function as status
> indicators for my gumstix.
>
> Do you have any suggestion?

I've never tried driving a buzzer, but presumably you could. You'd
need some type of driver circuitry.

There is a PWM output on the gumstix which might be usable. You'd need
to look at the frequency range that it can produce.

You Should be able to use an ordinary speaker with a simple circuit like this:
<http://www.sixca.com/micro/mcs51/music51/index.html>

You just need to provide a square wave on the P2.0 line with the
frequency you'd like to produce.

--
Dave Hylands
Vancouver, BC, Canada
http://www.DaveHylands.com/

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[Dave Hylands]

Hi Edward,

> Oops, I didn't use a current-limiting resistor; I'll go get one.
>
> The LED I got is labeled 'Can be driven directly with 3-12VDC', maybe it's
> got an integrated resistor but it looks very ordinary and small.

Could be - I know that there are LED with integrated resistors. You'd
need to check the datasheet for your particular LED.

> As for the buzzer, I didn't know I would need a driver circuit for the
> buzzer. I'll figure it out.
>
> The buzzer I got is labeled, 'Operating Voltage: 3-8Vac', 'Frequency:
> 2400Hz'.

So that sounds like a piezo. I think it can be hooked up the same way.

> Also, on the example circuit what does P2.0 mean?

That's the label for the GPIO pin that particular example used
(different processor).

--
Dave Hylands
Vancouver, BC, Canada
http://www.DaveHylands.com/

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