How to measure clock frequency of C430F5137 using programming

Question

I am using CC430F5137 system on chip.From the data sheet I got to know it uses 26MHz clock for the radio. To verify that,How do I measure the radio clock frequency by using MSP430 programming?

Any suggestions please....

Is there any timer/counter that is connected to radio clock?

Thanks.

Couldn't you just run a program that executes 26 million CPU instructions and times how long that takes (it should take 1 second if it's exactly 26MHz)? — Greg, Jul 18 '13 at 05:35
@PartiallyFinite, it depends on how many instructions it can execute per clock cycle (not always one). — Brian Cain, Jul 18 '13 at 05:38
@BrianCain true; you'd need to multiply that number by the number of instructions per clock cycle — Greg, Jul 18 '13 at 05:40
I am not talking about the clock of the CPU.But radio crystal(that is used for all packet handling stuff). — Sandeep Reddy Goli, Jul 18 '13 at 05:58
@NPE I was making sure that the radio clock runs at same frequency as specified in data sheet. — Sandeep Reddy Goli, Jul 18 '13 at 05:59
@SandeepReddyGoli: Get an oscilloscope out and look at the clock signal. — NPE, Jul 18 '13 at 06:04
If you can't trust the data sheet, how can you trust, say, that the MSP430 code will do what *its* data sheets tell you? — Damien_The_Unbeliever, Jul 18 '13 at 06:04
@Damien_The_Unbeliever Most clocks generally don't tick as expected .There will always be drift.Yes I am bit sceptic ,but making sure that it performs as expected. — Sandeep Reddy Goli, Jul 18 '13 at 06:13
@NPE that’s my question ,how do I get the radio clock signal? Is there any way that I could map the clock signal to one of the pins and then check it on oscilloscope. — Sandeep Reddy Goli, Jul 18 '13 at 06:21

score 1 · Answer 1 · answered Aug 27 '13 at 08:06

To measure the RF clock (26 MHz) with an oscilloscope, you need to:

1 - output the clock from the radio module to the core, e.g. through the signal GDO1 (internal signal between the RF SoC and the core). To do that, adjust the corresponding value in the RF config table, see 25.3.5 of the CC430 family user guide. To use GDO1, put 0x30 (RFCLK/1) in IOCFG1. See Table 25-21 if you need other dividers than 1 (depending on the limitations of your measuring equipment).

2 - map the radio module's signal GDO1 to a free IO pin.

PMAPKEYID = PMAPKEY;    // Get write-access to port mapping regs
P2MAP6 = PM_RFGDO1;     // Map radio GDO1 to output pin 2.6.
PMAPCTL |= PMAPRECFG;   // Allow for future port map configurations.
PMAPPWD = 0x00;         // Lock Port mapping

Set also the SEL and the DIR bits for the IO pin you are using.

3 - an oscilloscope (or frequency counter) that can measure 26 MHz accurately enough for your needs.

Note: measuring MCLK might not be accurate enough, its generation going through other disturbing stuff such as FLL...

score 0 · Answer 2 · answered Jul 22 '13 at 13:11

The CC430 family (similar to the other MSP430 family) can output its MCLK (or SMCLK) signal through a GPIO configured for that operation. MCLK is the same clock used for the radio peripheral. This is the signal you would want to measure on an oscilloscope.

The CC430 specifically has a port mapping controller designed to mux these functions to a designated GPIO. If you take a look at the CC430 Family User's Guide (http://www.ti.com/lit/ug/slau259e/slau259e.pdf), section 9 outlines the port mapping controller. Also, use the datasheet (http://www.ti.com/lit/ds/symlink/cc430f5137.pdf) to determine how the PxSEL and PxMAP registers must be configured for this secondary GPIO function - this can generally be found in the "input/output schematics" section.

The following is not the exact solution, but should be a guide for you. Please take a look at the following forum post: http://e2e.ti.com/support/microcontrollers/msp430/f/166/t/19075.aspx

How to measure clock frequency of C430F5137 using programming

2 Answers2