Project

General

Profile

RFM12B AFC settling

Added by JohnO over 3 years ago

I have been developing a sketch to ‘find’ the centre frequency of my Jeelink by scanning around the appropriate frequency by requesting an ACK to a 32 byte packet. All appears fine except that on first power on the RFM12B finds a frequency from a limited band. If the scan of the frequency is scanned again the responding frequency range is wider. This is reproducible and no doubt within the scope of Martyns understanding.

0 RF12Tune3 0x1482
Scanning up started 1700 /- 20
Node Allocation 1
Scan up complete 1680-1689
Scanning down started 1700
/- 20
Scan down complete 1681-1691
Centre frequency offset is 1685
New Node Number is 1
81D106955246313254756E65330000000000000000000000000000000000FC10
0 RF12Tune3 0xFC10
0
DelayingScanning up started 1685 /- 20
Scan up complete 1668-1690
Scanning down started 1685
/- 20
Scan down complete 1667-1691
Centre frequency offset is 1678
81D1068E5246313254756E65330000000000000000000000000000000000FC2F
0 RF12Tune3 0xFC2F
0
DelayingScanning up started 1678 /- 20
Scan up complete 1667-1688
Scanning down started 1678
/- 20
Scan down complete 1667-1691
Centre frequency offset is 1678
81D1068E5246313254756E65330000000000000000000000000000000000FC2F
0 RF12Tune3 0xFC2F
0
Delaying

The behaviour is improved if the frequency range scanned is increased to +/- 30 units of offset.

Perhaps these little chaps don’t open up their AFC’s unless stretched into other bands.


Replies (4)

RE: RFM12B AFC settling - Added by Castor01 over 1 year ago

Hi John!

I am now trying to establish a reliable communication between two JN. And your work seems very interesting. Any chance you post your sketch?
Best regards
Pierre

RE: RFM12B AFC settling - Added by JohnO over 1 year ago

Hi Pierre,

The code is old but still of interest to me. It is on Github at https://github.com/jcw/jeelib/tree/RFxConsole/examples/RF12/RF12tune3

The config layout has changed since the code was written. I think there is still a need to have code to do the RF tuning especially when interworking RF12B with RFM69 devices.

RE: RFM12B AFC settling - Added by JohnO over 1 year ago

If you have a specific issue it is possible to tune manually using the 'o' offset command with rf12demo.ino loaded up on both nodes.

RE: RFM12B AFC settling - Added by Castor01 over 1 year ago

Thank you SO MUCH for your very quick answer!
I will have a look tomorrow morning on your code, it will be very usefull for me.
I keep you advise if i can find something like 'automatic frequency tuning'...
Pierre

    (1-4/4)