Hi,
On 07.07.2012 13:42, Francesco Gugliuzza wrote:
Hi Leif! Nice work, and I'm glad to hear my post inspired you, even if my code didn't work at all!
Your code was changing settings of the RF- and IF-AGC, which do nothing more than modulating the AGC_RF and AGC_IF outputs of the RTL2832, which are connected to the GAIN0/GAIN1 inputs of the E4000. But since we're using the serial interface gain control mode, enabling the RF/IF-AGC won't have any effect, because the GAIN0/1 inputs are ignored.
I'm now setting 0x05 (0000 0101) instead of the original 0x25 (0010 0101) or your 0xd5 (1101 0101), to avoid setting unknown bits, and it seems to have the same effect (I see an about 10 dB noise floor drop when on minimum gain with no signal).
That's also what I observed, clearing bit 5 is enough to disable the AGC. I also noticed that both DAGC gain registers (page 1, 0x12 and page 0, 0x17) have no effect once bit 5 in the settings register is cleared. The control logic still seems to operate though, which can be observed by reading register 0x05 in page 3.
Regards, Steve