MSP-EXP430FR4133: MSP-EXP430FR4133

Hi Malcolm,

Can you refer me to where the enhanced clock mode is specified in the MSP430FR4133 data sheet? I only see 16MHz operation specified for this device.

BR,

Leo

Hi Leo,

I see the reference to to enhanced clock mode in the: 

"MSP430FR4xx and MSP430FR2xx family User's Guide"

Table 3-10. CSCTL6 Register Description

3-2 XT1HFFREQ RW 0h The XT1 high-frequency selection. These bits must be set to appropriate
frequency for crystal or bypass modes of operation. (1)
00b = 1 MHz to 4 MHz
01b = Above 4 MHz to 6 MHz
10b = Above 6 MHz to 16 MHz
11b = Above 16 MHz to 24 MHz (available in enhanced clock system only)

I see the reference to "available in enhanced clock mode" and I would like to understand how to (or if you can) set the clock greater than 16MHz.

My objective is to get the MSP-EXP430FR4133  communicating with the SPI to sample the ADS7042 at 600-700 ksps. I can get the SPI clock to 1MHz, but appears that I need a higher SPI clock of 1MHz to achieve that 700 ksps.

If you can shed any light on the enhanced clock, or a coding solution to achieve the 700 ksps that would be appreciated.

Thanks,

Malcolm

Hi Bruce,

Yes. I did see where the manuals reference the 8MHz clock. The problem that I am running into is that when I try to set the SPI clock above 1MHz, the SPI clock signal becomes distorted (the clock signals are no longer peak to peak and are not clean). So I was wondering if I needed to enable the Enhanced Clock System to produce a faster base clock to feed the SPI clock. Hence my questions was more about the Enhanced Clock Mode.

So I agree that the manuals do say 8MHz SPI, but I can only get 1MHz.

Any thoughts?

Thanks,

Malcolm

The Enhanced Clock System is something you have or you don't -- you don't need to switch it on.

How bad are the signals (at 8MHz) actually? I've found most SPI slaves fairly forgiving. How does it look at 4MHz?

To keep things in perspective, if you could run the SPI at 8MHz (non-stop), you would get 500ksps, which with a 16MHz MCLK gives you 32 CPU clocks, or something like 5-8 instructions, per sample. The FR4133 doesn't have DMA, so you'll need to feed the Tx side and then fetch the Rx bytes and make words out of them , which will easily take up 3/4ths of those instructions. I think you'll find you don't have any time left to do anything with the data. Once you estimate how much CPU your actual data processing will take, you might find that a 4MHz or even 1MHz SPI is adequate.

Hi Bruce.

I was able to get the SPI running at 8MHz and close to 400k samples. I changed the SPI source clock.

You are correct with your calculations. I knew it would be tight, but had a ADS7042 and wanted to see what I could achieve.

Do you have any recommendations for dev kits that I might be able to use to achieve the 600ksps to 700ksps?

Thanks

Malcolm