Author Topic: Recommendations for Automatic Frequency Correction (AFC) settings of RFM69HW  (Read 693 times)

chrisb2

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  • Posts: 6
  • Country: nz
I have configure my transmitter with Fdev=2501Hz and bit rate 1200:

Code: [Select]
radio.writeReg(REG_BITRATEMSB, RF_BITRATEMSB_1200);
radio.writeReg(REG_BITRATELSB, RF_BITRATELSB_1200);
radio.writeReg(REG_FDEVMSB,0x00);
radio.writeReg(REG_FDEVLSB,0x29); // 52->5002Hz, , 30->2928Hz, 29->2501Hz, 21->2013Hz(x)

and my receiver with RxBw=5200Hz and bit rate is 1200:

Code: [Select]
radio.writeReg(REG_BITRATEMSB, RF_BITRATEMSB_1200); // Bit Rate (p20)
radio.writeReg(REG_BITRATELSB, RF_BITRATELSB_1200);
radio.writeReg(REG_RXBW, RF_RXBW_DCCFREQ_010 | RF_RXBW_MANT_24 | RF_RXBW_EXP_6); // RxBw 5200Hz (p26)

The ratio of Fdev to RxBW is based on https://lowpowerlab.com/forum/index.php?action=post;quote=560;topic=144.0;last_msg=565.

This configuration seems to work well, with reasonable range at low power settings. From reading the data sheet it seem to me that AFC (section 3.4.15 and 3.4.16) should result in a further improvements in sensitivity. However I have played with a whole heap of different setting from these two sections, but mostly receive no data (very occasionally I see 1-4 reading after upload, but no more).

Can anyone help with some workable setting?

thanks,
Chris