I'm working with a customer who is setting up some manufacturing test. They are putting the device into test mode using HCI commands from BTool:
- HCI_Reset
- HCIExt_seTxPowerCmd
- HCI_LE_EnhancedTransmitterTest
They are realizing that their is a frequency shift from the carrier when setting the channel, the frequency is being observed on a spectrum analyzer:
I realized that there is a frequency shift when selecting the channel. For instance, channel 0 should be transmitting at 2404Mhz but the signal is transmitting at 2402Mhz, another example, if I set the channel to 17 the unit is transmitting at 2436Mhz instead of 2440Mhz so the frequency deviation is wider when using channel 17. I thought that the issue was related to the frequency tuning of the 48Mhz Crystal so I modified the SET_CCFG_MODE_CONF_XOSC_CAP_MOD register but the frequency shift cannot be corrected because of the high frequency shift (4Mhz worst case).
I use an evaluation board (CC2652R1) and I did a test comparing RF Studio 7 against BTool; I compared a continuous TX signal Unmodulated in different channels and the frequency shift was detected when using BTool but the frequency shift is not present when using RF Studio 7.
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- Is there any other command I’m missing in BTool that is causing the frequency shift in the TX channel?
- Is there any issue with BTool on regards to txChannel?
I think that this is normal and expected, but my knowledge in this area of RF is limited and I could use some expert explanation as to if the observation is correct, and why.
Thanks,
Stuart
