LVEA MCB2300 / LPC2378 PWM Frequency Stuck at 900 Hz

[JohnGrove]

Hi folks,

I'm working on ARM project that uses a PWM signal to drive a dc motor, but for some reason the PWM frequency coming out of the LPC2378 is always 900 Hz.

I've tried setting the PWM frequency in the EIO properties dialogue to 100, 200, 700, 1000, 2000 Hz, rebuilding the whole project several times etc, but I always get 900 Hz physically output - any ideas why this might be, or how I can change it?

(I'm prepared to delve into the c. files if necessary, if someone can point me in the right direction!)

Thanks,

John.

[JohnGrove]

Update:

Maybe the problem lies in the PWM initialisation code in "MCB2300_PWMInit.vi" but I can't check this as the block diagram only contains a C function call.

Any help appreciated!

[JohnGrove]

Update 2:

OK, I narrowed this down some more.

Using the standard MCB2300 target, the system responds correctly to the PWM frequency settings, but using the generic LPC2378 target, it sticks at 900 HZ.

Also, the physical 900 HZ is output when the frequency is set to 1000 HZ. i.e. the "setting" actually sticks at 1000 HZ, which almost makes sense as 1000 HZ is the default value.

So, just need to find how to persuade the generic target to respond to the frequency setting?

[JTG_Wilson]

Hi John,

What version of LabVIEW embedded for ARM are you using?

There are a couple of old Corrective Action Requests in our database for issues simialr to yours that should be fixed in the lastest versions.

[JohnGrove]

Hello James,

I'm actually using LVEA 2010, but I will try 2011 shortly and check if the problem is still there....

[JohnGrove]

Checked in LVEA 2011 and can confirm that the issue is still there.

[akonni]

Can you post your snippet of your code?  The LVEA code for PWM is very finicky (at least for LM3S8962 target).  So, depends on how you wire up the vi, the PWM may or may not work. 

[JohnGrove]

Akonni,

There isn't any LabVIEW code worth looking at for the LPC2378 PWM, you just wire an integer between 0 & 100 straight to the PWM output node!

All the PWM settings are carried out globally in the project tree, there are no PWM settings available from within a VI....

[kamyar]

Hi

I have same problam with my ARM and PWM

have u find any solution yet?