CC1101: CC1101

Have you tested if TX works on the modules you fail to receive the signal? Do you see a signal on the air and is it the correct frequency? 

The signal on the air there is.

I just test the TX and CC1101 doesn't transmit, but I don't know why.

I'm using the sniffer of Texas.

Do you think that the CC1101 transmit on different frequency from sniffer device?

Do you have a spectrum analyzer or similar enabling to to measure what is on the air? 

First: Have you verified that SO goes low after CSn goes low before starting to use the SPI interface? Do you manage to read back the registers you set? 

I need more details on how you use the chip, both from a HW and a SW perspective to be able to help you. 

I checked the SPI signals and they are OK.

When  I change the CC1101, I check that its machine state register is OK.

I think that the problem is about PLL.

When I prower on the device, it begins to receive after some minutes. This time is not constant.

Could you post the part of your code that shows how you setup the device and how you set it in RX. Do you use SCAL or e MCSM0.FS_AUTOCAL to calibrate the VCO? Could you share a schematic of your module and the xtal used? 

The schematic is:

SC1416B1.pdf

and XTAL is:

CVQ266S RALTRON RH100-26.000-12-F-1010-EXT-TR.pdf

and a piece of my coce to drive the CC1101 is:

void CC1101handle.pdf

I hope it clear.

The MCSM0 register value is 0x18.

I believe what you have to do is to set the CC1101 to send a CW and measure the frequency it send on to do basic RF testing.

From the datasheet of the xtal I could not see the Cload this requires. From the schematic: Are the load caps 18 pF? 

The load caps in the schematic are 18pF.

I don't understand why some boards work correctly and other not.

The XTAL Cload is 12pF and the tollerance is +/- 10ppm.

I measured the frequency of XTAL and it is 26,0013MHz.

The boards that work correctly send a CW on 868,3MHz and the boards that don't work send a CW on 868,35MHz.

I don't understand the reason.

- 18 pF sounds a bit low. 18 pF gives a Cload of 9 pF + parasitics. I would expect 1 -2 pF in parasitics. Try to increase  the parasitics slighly to get a RF frequency that is exactly 868.300 MHz.