Hello, I am trying to find the exact frequency to which I transmit from another transmitter, with the rssi approximating me up to + - 0.5 mhz,
however it is not enough to decode the signal correctly. Is there any value to help me find it more accurately, or to decode with a higher tolerance range?
Thank you
Javier,
We have a register inside the CC1101 that will provide an estimate of the frequency difference (or error) between the TX node and the RX node for any given packet.
Here is a quick snapshot from our SmartRF Studio online guide.
Here is a function that we have developed to show to convert this information into Hertz.
/* Select the correct XTAL frequency for the hardware */
#define SCALING_FREQ (float)((RF_XTAL)/65.536)
#define SCALING_FREQEST (unsigned long)((RF_XTAL)/16.384)
/******************************************************************************
* @fn radio_freq_error
*
* @brief Estimate the frequency error from two complement coded
* data to frequency error in Hertz
*
* input parameters
*
* @param freq_reg_error - two complement formatted data from transceiver
*
* output parameters
*
* @return freq_error - 32 bit signed integer value representing
* frequency error in Hertz
*
*/
int radio_freq_error(void) {
long freq_error_est;
unsigned char regState;
/* Read marcstate to check for frequency error estimate */
trx8BitRegAccess(RADIO_READ_ACCESS | RADIO_BURST_ACCESS, FREQEST, ®State, 1);
/* Calculate the frequency error in Hz */
freq_error_est = regState;
/* the incoming data is 8 bit two complement format, separate "sign" */
if (freq_error_est > 128) {
freq_error_est = freq_error_est - 256;
}
/* convert the data to hertz format in two steps to avoid integer overuns */
freq_error_est = freq_error_est * (long)SCALING_FREQEST;
return ((int)freq_error_est);
}
Hope this helps.
Regards,
/TA
