LPC84X FRO Configuration Example

[mark_stokes]

The datasheet states there is an API ROM Routine for setting the FPO frequency.  It shows how it works (parameter, etc.), but it doesn't show how to use it.  I don't see anywhere what the API command code is (I assume it's like the IAP commands, but don't know).

Is there any example code (preferably for IAR) that shows how to set the frequency of the FRO?  Something that shows implementation of set_fro_frequency() referenced in the manual.

And let me just complain one more time about not updating LPC_Open for the LPC84X.  I realize there would be some work involved, but since you're not doing it, I'm wasting good development time making it work so I can use it (port my existing LPC824 code over) instead of developing my application.

Thanks

[jeremyzhou · Accepted solution]

Hi Mark Stokes,

Thank you for your interest in NXP Semiconductor products and 

for the opportunity to serve you.

Regarding to calling the set_fro_frequency() API, you can refer to LPC845 example code bundle.

LPC84x 30MHz|ARM Cortex-M0+|32-bit MCUs|NXP 

And good news: LPC845 SDK will be released in the Q1, 2018.

Have a great day,
TIC

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[NeoTsai]

LPCopen? or MCU SDK?

[jeremyzhou]

Hi Neo Tsai,

The bundle type is different from the SDK or LPCOpen, it doesn't contains abstract level and configures the hardware peripheral registers directly.

Hope this is clear.

Have a great day,
TIC

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[mark_stokes]

Thanks for the reply.  I realized I had already downloaded it and found the implementation.  This leads me to another question.  I don't really like the way this uses #defines to setup the FPO frequency.  It looks like the intent is to have it set once for a project and never change it.  While I'm writing a library for the clock system, I'm wanting to give the opportunity to change the base FPO clock and I can use the example you send above.  However, there is no way for the code (after a reboot for example) to know what the base frequency is.  I see how I can use the ReadFAIM function to get the div8 value and the FROOSCCTRL to determine the fpo_oscout value (needed to calculate baud rates, I2C rates, etc., but without any access to the result of a previous call to set_fro_frequency(), this can't be calculated.