• State Resolved
  • Locked Locked
  • Replies 1 reply
  • Subscribers 79 subscribers
  • Views 766 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

EZ430-RF2500T: What is my theoretical TX speed? (Sampling from 16-bit spi, tx over radio)

James Trafny
Intellectual 510 points

Part Number: EZ430-RF2500T
Other Parts Discussed in Thread: MSP430F2274, CC2500

Hello again!

I'm struggling my way through trying to get an End Device set up using the EZ430-RF2500T, but while I'm working on it I'm wondering what data transfer speeds I can even expect when I'm done. 

I understand that the MSP430F2274 has a 16Mhz clock, and an 8-bit SPI bus.  I understand that the MSP430's communicate with each other using the onboard CC2500 via the same 8-bit SPI bus. (I hope I'm right so far.)

So, I have an AS5047P (magnetic rotary encoder [its very cool]) that communicates over 16-bit SPI (up to 10 MHz) that will be connected to the End Device.  The data from that AMS board (all 16 bits) need to make it to the AP, so I will need two SPI rx/tx cycles to move the data from the AMS board into the MSP430, and then two more rx/tx cycles to move the data from the MSP430 to the CC2500. 

If we were to just consider moving that raw data around, how could I calculate how many samples per second I could receive at my Access Point?  I assume that it takes more than a single clock cycle to read from the SPI bus, and a few clock cycles to transmit/receive the data, but I'm not really sure how to figure that out; and even if I did, how to do the final calculations.

I hope you can help me understand the capabilities of these devices!

Thank you in advance!
-James

  • 0
    TI__Guru 56685 points
    Hello James,

    One thing to keep in mind here is that the MCLK speed of the MSP430 and the SPI CLK speed of the communication lines can and will most likely be independent of each other. It takes one clock cycle to fill SPI TX Buff (or retrieve from SPI RX Buff), but the speed of this clock cycle will be different from the SPI CLK speed. Once you fill the SPI Buff, every tick of the SPI CLK is one bit transferred. You can technically drive the SPI CLK as fast as the max frequency of the part, but you wouldn't be able to send/retrieve data from the buffer lines in time. You also have to consider what the max SPI Speed the attached device can handle as well. Typically, SPI lines are run int he range of a few MHz, while the MSP430 MCLK is run far faster to minimize interruption by the CPU. For more information about SPI on MSP430 please see the User Guide for your device and the following application note. www.ti.com/.../slaa734

**Attention** This is a public forum