Improved README

README.md

@@ -4,7 +4,7 @@ This is a Flipper Zero app to receive and decode, or simulate, multiple time sig
 
 ## Protocol support
 
-### DCF77 (DE, 77.5 kHz)
+### DCF77 (Europe, Germany)
 
 ![](screenshots/v0.1/menu_dcf77.png) ![](screenshots/v0.1/dcf77_1.png) ![](screenshots/v0.1/dcf77_2.png)
 
@@ -14,18 +14,54 @@ This is a Flipper Zero app to receive and decode, or simulate, multiple time sig
 - 1 bit per second is transmitted by reducing carrier power at the beginning of every second.
 - The transmission encodes time, date as well as catastrophe and weather information (encrypted, not decoded).
 
-### MSF (UK, 60 kHz)
+### MSF (Europe, United Kingdom)
 
 ![](screenshots/v0.1/menu_msf.png) ![](screenshots/v0.1/msf_1.png) ![](screenshots/v0.1/msf_2.png)
 
-[MSF (Time from NPL/Rugby clock)](https://en.wikipedia.org/wiki/Time_from_NPL_(MSF)) is broadcasted from Anthorn in the UK ([54.9116,-3.2785](https://www.openstreetmap.org/?mlat=54.9116&mlon=-3.2785#map=5/54.91/-3.27)) and requires an antenna tuned to 60 kHz (as does [WWVB](#WWVB)).
+[MSF (Time from NPL/Rugby clock)](https://en.wikipedia.org/wiki/Time_from_NPL_(MSF)) is broadcasted from Anthorn in the UK ([54.9116,-3.2785](https://www.openstreetmap.org/?mlat=54.9116&mlon=-3.2785#map=5/54.91/-3.27)) and requires an antenna tuned to 60 kHz (as does [WWVB](#wwvb-north-america-us)).
 
 - The radio transmission can be received over most of western and northern Europe.
 - The transmission encodes time, date as well as DUT1 bits (difference between atomic and astronomical time).
 - The app only supports the slow code at 120 bits per minute, of which only 60bits  are encoded.
+- Same frequency as WWVB - in Europe you will receive this signal through a WWVB receiver.
 
-### WWVB (US, 60 kHz)
+### WWVB (North America, US)
 
-[WWVB](https://en.wikipedia.org/wiki/WWVB) is on the backlog for the Longwave app.
+[WWVB](https://en.wikipedia.org/wiki/WWVB) transmits on 60 kHz and is on the backlog for the Longwave app.
 
-If you're based in the US and would like to help: PRs are welcome!
+If you're based in the US and would like to help: PRs are welcome!
+
+## GPIO modules
+
+The app supports a demonstration mode as well as GPIO mode. For GPIO mode, external modules are required.
+
+In GPIO mode the following configuration is available (per protocol):
+- GPIO data: use "inverted" if the module outputs logic high to the data pin when the sender signal is low (hopefully rare).
+- Data pin: this configures the receiving pin on the flipper, C0 is the default and recommended pin.
+
+### Supported modules
+
+The following shows modules that I own and have been successfully tested for reception.
+
+#### 77.5 kHz module (DCF77)
+
+![](screenshots/modules/module_775.jpg) 
+
+You can find this type of module by searching for "DCF77 module" in any electronics online shop.
+
+#### 60.0 kHz module (MSF, WWVB)
+
+![](screenshots/modules/module_600.jpg) 
+
+Search for "WWVB module" in any electronics online shop. 
+This applies even if you want to receive MSF instead: they use the same frequency.
+
+### Pinout
+
+The modules I checked are pretty much the same, here is the common pinout configuration I found and tested.
+Please check with the manufacturer, as yours might be different and you may cause damage by wiring the module incorrectly. 
+
+- **VDD**: flipper pin 9 (3V3)
+- **GND** / unlabeled: flipper pin 11 (GND)
+- **PON** / **P**: power on, asks for "logic low", using flipper pin 11 (GND)
+- **OUT** / **T**: the data signal, using flipper pin 16 (C0)