Update README.md

Readme.md

@@ -16,20 +16,20 @@ Plug a wire on GPIO 18, means Pin 12 of the GPIO header ([header P1](http://elin
 **rpitx** is the main software to transmit. It allows to transmit 
 	- from **IQ** files *.iq (could be generated by external software like gnuradio or by some few examples of modulations).
 	- from **Frequency/Time** files *.ft (generally used implement easily digital modes)  
-
-Usage:rpitx [-i File Input][-m ModeInput] [-f frequency output] [-s Samplerate] [-l] [-p ppm] [-h] 
--m            {IQ(FileInput is a Stereo Wav contains I on left Channel, Q on right channel)}
-              {IQFLOAT(FileInput is a Raw float interlaced I,Q)}
-              {RF(FileInput is a (double)Frequency,Time in nanoseconds}
-       	      {RFA(FileInput is a (double)Frequency,(int)Time in nanoseconds,(float)Amplitude}
-	      {VFO (constant frequency)}
--i            path to File Input 
--f float      frequency to output on GPIO_18 pin 12 in khz : (130 kHz to 750 MHz),
--l            loop mode for file input
--p float      frequency correction in parts per million (ppm), positive or negative, for calibration, default 0.
--d int 	      DMABurstSize (default 1000) but for very short message, could be decrease
--h            help (this help).
-
+    
+    Usage:rpitx [-i File Input][-m ModeInput] [-f frequency output] [-s Samplerate] [-l] [-p ppm] [-h] 
+    -m            {IQ(FileInput is a Stereo Wav contains I on left Channel, Q on right channel)}
+                  {IQFLOAT(FileInput is a Raw float interlaced I,Q)}
+                  {RF(FileInput is a (double)Frequency,Time in nanoseconds}
+           	      {RFA(FileInput is a (double)Frequency,(int)Time in nanoseconds,(float)Amplitude}
+    	      {VFO (constant frequency)}
+    -i            path to File Input 
+    -f float      frequency to output on GPIO_18 pin 12 in khz : (130 kHz to 750 MHz),
+    -l            loop mode for file input
+    -p float      frequency correction in parts per million (ppm), positive or negative, for calibration, default 0.
+    -d int 	      DMABurstSize (default 1000) but for very short message, could be decrease
+    -h            help (this help).
+    
 <h2> Modulation samples </h2>
 Some modulations are included in the software and can be easily extended. They create files which could be ingest by rpitx.
 Some output in IQ (like ssb) other in FT(like sstv)