Re: [microblaze-uclinux] PWM Signals and uClinux

[John Williams <jwilliams@xxxxxxxxxxxxxx>]

Hi Briabn,

Brian Estrada wrote:
> For now, I would like to generate a high signal from the onboard D-to-A
> converter next to the rotary knob on the board. 

What do you mean "a high signal"?  A logic high (3.3 / 2.5 V or 
whatever), or something else?

If this is all you need, just instantiate a GPIO, wire the output to a 
pin on the board, and use that?

Is there a driver written
> for this specific interface? I would like to try to avoid using SPI, but
> have heard that this interface uses SPI. Is this true?

The D-A on the Spartan Starter boards use SPI, that is correct. 
PetaLinux contains a char drieer for the xilinx SPI controller, so it 
shouldn't be too difficult to use.  Instatiate the controller, enable 
the driver, write a simple user app to talk to it, and off you go.

Regards,

John

 If it is, is there
> any other interface that can output this signal, like one of the 6-pin
> headers? Again, a high signal is all we need for now. Thanks for any help.


> Brian
>
> -----Original Message-----
> From: owner-microblaze-uclinux@xxxxxxxxxxxxxx
> [mailto:owner-microblaze-uclinux@xxxxxxxxxxxxxx] On Behalf Of John Williams
> Sent: Wednesday, May 28, 2008 4:21 PM
> To: microblaze-uclinux@xxxxxxxxxxxxxx
> Subject: Re: [microblaze-uclinux] PWM Signals and uClinux
>
> Hi Brian,
>
> Brian Estrada wrote:
> > Has anyone had experience with creating pulse width modulated signals 
> > with uClinux and a Spartan 3E starter board? Or even just generating a 
> > high signal from one of the onboard digital-to-analog converters or 
> > through SPI. If so, I would be very grateful for some example code or a 
> > point in the right direction. Thanks.
>
> A simple char device driver over an xps_timer in PWM node wouldn't be 
> difficult to accomplish.  The PWM output would itself be hardware 
> accurate in terms of duty cycle, however changes in the PWM amplitude 
> would be subject to userspace/kernel latencies.
>
> Broadly what are you trying to achieve?
>
> Regards,
>
> John
>
>
>
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