7 Jul
2012
7 Jul
'12
1:57 p.m.
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