Frequency counter using LPC55x

[dav1]

Looking to achieve a ~1ppm frequency counter on the LPC55x

I noted that the data sheet mentions a "frequency measurement unit" but the end of that chapter seems to be truncated/missing. Is there more info around this or even an app-note?

I guess we could make use of the internal PLL or a 0.1ppm external TCXO to feed a counter, but there needs to be some tight sync for phase and captures, was hoping there are some features built-in for this.

Any input on this subject would be great!

[xiangjun_rong]

Hi,

If you use LPC556x/2x, pls refer to the section 11.6.1 Frequency measure function in UM11126.pdf, which can be downloaded from the link:

https://www.nxp.com/products/processors-and-microcontrollers/arm-microcontrollers/general-purpose-mc...

Regarding accuracy of the frequency measurement, I think the basic mechanism of the accuracy depends on two factors, the first is the reference clock accuracy, the second is the result value of CAPVAL, the larger the value of CAPVAL is, the more accurate the target frequency is.

Hope it can help you

BR

XiangJun rong

[xiangjun_rong]

Hi,

If you use LPC556x/2x, pls refer to the section 11.6.1 Frequency measure function in UM11126.pdf, which can be downloaded from the link:

https://www.nxp.com/products/processors-and-microcontrollers/arm-microcontrollers/general-purpose-mc...

Regarding accuracy of the frequency measurement, I think the basic mechanism of the accuracy depends on two factors, the first is the reference clock accuracy, the second is the result value of CAPVAL, the larger the value of CAPVAL is, the more accurate the target frequency is.

Hope it can help you

BR

XiangJun rong