update app notes

doc/app_notes/iq.md

@@ -12,7 +12,7 @@ We implement the **IQ sample capture** with interesting extensions: many **trigg
   ./monitor_ch.sh sdr0 11
   (Monitor on channel 11. You can change 11 to other channel that is busy)
   insmod side_ch.ko iq_len_init=8187
-  (for zed, adrv9364z7020, zc702 board, 8187 should be 4095 because they have smaller FPGA)
+  (for smaller FPGA (7Z020), iq_len_init should be <4096, like 4095, instead of 8187)
   
   ./side_ch_ctl wh11d4094
   (Above command is needed only when you run with zed, adrv9364z7020, zc702 board)
@@ -31,7 +31,7 @@ We implement the **IQ sample capture** with interesting extensions: many **trigg
   ```
   cd openwifi/user_space/side_ch_ctl_src
   python3 iq_capture.py
-  (for zed, adrv9364z7020, zc702 board, add 4095 as parameter!)
+  (for zed, adrv9364z7020, zc702 board, add argument that euqals to iq_len_init, like 4095)
   ```
   The python script needs "matplotlib.pyplot" and "numpy" packages installed. Now you should see 3 figures showing run-time **IQ sample**, **AGC gain and lock status** and **RSSI (uncalibrated)**. Meanwhile the python script prints the **timestamp**.
   

doc/app_notes/iq_2ant.md

@@ -38,6 +38,7 @@ In this app note, we show how to use the dual antenna I/Q capture to capture the
   - On remote computer, run
   ```
   python3 iq_capture_2ant.py
+  (if smaller FPGA, like z7020, is used, add a argument that equals to iq_len_init, like 4095)
   ```
   Above script will plot the real-time rx0 and rx1 I/Q captured each time trigger condition met. Meanwhile the script also prints the maximum amplitutde of the rx0 and rx1 I/Q samples. Check the 3rd column that is displayed by the script: Those small value printing indicate noise (most probably, because the rx1 gain is very low). The big value printing indicate a packet from rx1 (although rx1 has very low gain, rx1 is very close to the peer WiFi node). Go through the noise and the packet max I/Q amplitude numbers from rx1 printing (the 3rd column), and decide a threshold value that is significantly higher than the noise but less than those big values (packets).
   - Set trigger condition to 29, which means that rx1 I/Q is found larger than a threshold while SDR is transmitting -- this means a collision condition is captured because rx1 I/Q implies the transmitting from the peer WiFi node. The threshold value is decided in the previous step (2500 is assumed here).