Tobias: On Mon, Oct 25, 2010 at 11:25 AM, Tobias Ang <[email protected]> wrote: > Hi, > I am currently working on generating an RSSI profile of a channel using a > TelosB mote with as high a sample rate as possible. At this moment, I am > only able to obtain a new RSSI value every 155 us although the CC2420 radio > provides a new RSSI value after it has been in the receive mode for 0.128ms > and for each subsequent symbol. I have also read in another paper that the > RSSI value is obtained at a sample rate of 62.5 KHz or every 16 us but this > was done on the Tmote Sky platform. I have tried a couple of solutions but > they do not seem to work. I would like to present them here for discussion. This sounds like a fun project...
> Initially, I wanted to increase the MSP430 clock rate but it has been > previously discussed that it is only possible with the Tmote Sky as the Rosc > is not populated on the TelosB. Please refer > to http://www.mail-archive.com/[email protected]/msg09808.html. This is true. I am aware of that. We're stuck with a maximum DCO frequency of about 3.8-4MHz on the telosb. > From Figure 6 in the TelosB datasheet, it shows that Timer B is connected > with CC2420 and I assumed that it determines the clock rate of the SPI bus. No. It only means that the time of the SFD interrupt can only be timestamped with the value of timer B. It does not constrain the SPI speed in any way. > I also tried to find out if there was a possibilty in increasing the baud > rate of the SPI bus. After checking msp430usart.h, it seems that the fastest > configuration of ubr : 0x0002, ssel : 0x02, which means that SMCLK(1 MHz) is > already the source and that as its source and with the smallest divisor of You can set SMCLK to tick at the DCO freq (~4MHz), by changing the SMCLK prescaler. This has a couple of side effects (constants/configuration values for DCO calibration, uard baud rate registers, microsecond timers, etc. need to be altered accordingly), but is certainly doable. Janos _______________________________________________ Tinyos-help mailing list [email protected] https://www.millennium.berkeley.edu/cgi-bin/mailman/listinfo/tinyos-help
