CC1125: Problem with data transmission using CC1125.

Hi Frank,

are the RF modules TI evaluation modules or from another vender? Would you have a link to the modules you have used?

What do you mean by "connected the RF receiver module to the custom transmitter board"? Do you mean that you are connecting the custom board with a coaxial cable to the receiver module?

I am using Transceiver Evaluation Board SmartRF TrxEB PCB rev 1.7.1 SN0x032A1 . The RF module connected to it is CC1120DK_EM_169 Rev 1.1.0. SN 00062D.

Yes, the custom board is connected to the receiver module via a coaxial cable.

Here is the link to the TI evaluation board. You can find the documentation for the 169MHz RF module at the same link.

https://www.ti.com/tool/SMARTRFTRXEBK#tech-docs

I think that the problem is with the custom module because the spectrum analyser plot does not show any modulation.

It's not clear from the above: The the custom board connected/ controlled by the TRXEB or does the custom board have a MCU controlling the CC1125? 

The custom board has an MCU controlling a CC1125 which is also on the custom board. Then the RF output of the CC1125 on the custom board is directly connected to the CC112X on the TI evaluation module via a coax cable. I am using SmartRF Studio 7 to setup the TI evaluation module and to view the data output of the CC112X on the TI evaluation module. The CC112X on the TI evaluation module is setup as a receiver only. The CC1125 on the custom module is setup as a transmitter only.

The spectrum looks like preamble (?), you can compare with the spectrum from the EVM controlled by SmartRF Studio.

For your custom board, it could be a setting or FW issue. Have you tried to just send a CW? Or just send random, modulated data, use the settings from Studio with these settings:

CC1125_2.pdf

CC1125_3.pdfAdded spectrum analyser traces for unmodulated carriers for the custom board and the TI evaluation module. Both boards appear to be very nearly identical. The problem appears to be something associated with data modulation. Can you give me a code example on how to setup data modulation ? I think that the register settings are fine. Configuring the TX FIFO may be the problem.

Hi Frank,

I went through you defined values for the registers and they look correct, considering the changes for the 38.4 MHz TCXO.

Do you also have the code where you write the settings to the CC1125?

5531.CC1125_3.pdfHere is the code. Note that I use many of the default register values eg SYNC, PREAMBLE etc. So these registers will not be in the code.

Also, RF frequency and RF power are set by other functions. However, there is no problem in setting RF frequency and RF power.

I suspect that I am not configuring the TX FIFO correctly.

Thanks for your assistance. I have managed to get the custom module to successfully transmit packets to the TI evaluation module.