Convert to QSD

README.md

@@ -4,11 +4,7 @@ Using RP2040 / Raspberry Pi Pico as a software-defined radio receiver.
 
 See the [blog post](https://blog.porucha.net/2024/pico-sdr/) for more information. Older code the article is mostly referring to can be found in the branch `old` and a more up-to-date approach in the branch `master`.
 
-This branch contains code to use RP2040 and some passives as a superheterodyne receiver. It is still very much work in progress.
+This branch contains code to use RP2040 with a 1:4 multiplexer and some passives as a quadrature sampling decoder receiver. It is still very much work in progress.
-
-## Circuit
-
-Please refer to [the simulation](https://www.falstad.com/circuit/circuitjs.html?ctz=CQAgjCBMB0CsCmBaMAGEAOW0AsLboHYA2SWSIsWMIkAtFaFFCWNBZMAKEoE5wV06ENiE8ekYULZpUTOfM4BzfoMnhU2NfU4AlED2ybERTeh41jmmfpHyZ0IrHAOn9OJ0goC4AMyQhiOa+RGiBNE4AkgBi3ESihiBh-LiJQehgBlAgPtA+INp6BkZ+NprUwiBOPnZy2bn5DQywnABOtGSJGRIEHUkydpwA7smhXSOpNCicAMaVIRMgjhZBMkjeyA7YYjzoXiGwPuJGYC6cADaLsMs0PRJ9+Yzy288vz4k5B8REPGAi2HSQHzoNb5GbtO5BW6NcBIIQnEzbIgmMCQOiwWDEZyOJTghpQ8raYZQpLoEQLKbDUkBIJFcmtbJxBbYEzkypTTwQVEQmiQSBGFY2ELySS1BhPV4SsTgcRyTgRcbIcSlTpK6w5HxDOahIJXNBkqYANygBG5DOpk3AGHQnmF9Ea7jaGm1NDAYB81warBxbv8DR9cItU1m-oWIbtYFhiTFzDi4lYkDA1oIQJQVnO4EBppD92jcklkqjj2YifQPhN5BIBgIgm8FOViokVJVEjrTYbuPbUwARhgiOs+TJsK79LXOAAPXtORCkPgGPjTq4VPkgHQABU8uHHtBNiU8eWtRhtFXKAHFVxEAPIAHQAzs0J8R56gaNaIMgUHkyjQz5fb+hNU6iQsoBJR1mIEhkrqWhbgQBAQIcGCAsIEHgN+57XjePCalBSTMvykycD2GRvpQEDMnkiBAqCE7ugE1A0ORnREJ+UCaAAggAdgALvAHEcQAhmCrruqGmasrmTAQPCQJXL8sDiD4PhuhiWLNAA9tklQon6PiwNgPhWHAZZIjsyImO6PCuEWEBoBIeQakAA).
 
 ## Software
 
@@ -34,4 +30,4 @@ Please refer to [the simulation](https://www.falstad.com/circuit/circuitjs.html?
 
 4. Open `grc/PicoSDR-WBFM.grc` in GNU Radio Companion, adjust carrier frequency to match your favorite FM radio station and press `F6`.
 
-5. Alternatively [gqrx](https://www.gqrx.dk/) works fine with `rtl_tcp` input mode. Maximum sample rate seem to be 400 ksps, above that the samples are dropped. Make sure to set LNA gain to 0, gain control is digital and does not provide any benefits unless you lower your sampling rate significantly.
+5. Alternatively [gqrx](https://www.gqrx.dk/) works fine with `rtl_tcp` input mode. Maximum sample rate seem to be 400 ksps, above that the samples are dropped. Make sure to experiment with LNA gain. It might be digital, but it's supposed to be somewhere north of 12 dB.

grc/PicoSDR-WBFM.grc

@@ -37,7 +37,7 @@ blocks:
   id: variable
   parameters:
     comment: ''
-    value: '88_200_000'
+    value: '94_615_000'
   states:
     bus_sink: false
     bus_source: false
@@ -49,7 +49,7 @@ blocks:
   id: variable
   parameters:
     comment: ''
-    value: '192_000'
+    value: '200_000'
   states:
     bus_sink: false
     bus_source: false
@@ -374,7 +374,7 @@ blocks:
     freq7: 100e6
     freq8: 100e6
     freq9: 100e6
-    gain0: '30'
+    gain0: '24'
     gain1: '10'
     gain10: '10'
     gain11: '10'

util/bridge.py

@@ -62,6 +62,10 @@ def bridge(frequency, device):
 
             print("Begin")
 
+            header = fp.read(12)
+            if header:
+                peer.send(header)
+
             try:
                 cmd = b""