From 4d11c06949a235ff75b5b5b2a5470007c04ffd74 Mon Sep 17 00:00:00 2001
From: madengr <rfengr00@me.com>
Date: Sat, 13 Jan 2018 15:01:59 -0600
Subject: [PATCH] Fixed DAC overflow, added UHD args and clock source

---
 gps-sdr-sim-uhd.py | 22 ++++++++++++++--------
 1 file changed, 14 insertions(+), 8 deletions(-)

diff --git a/gps-sdr-sim-uhd.py b/gps-sdr-sim-uhd.py
index 47bfc78..d5b418e 100755
--- a/gps-sdr-sim-uhd.py
+++ b/gps-sdr-sim-uhd.py
@@ -20,16 +20,11 @@ class top_block(gr.top_block):
         ##################################################
         # Blocks
         ##################################################
-        self.uhd_usrp_sink = uhd.usrp_sink(
-        	",".join(("", "")),
-        	uhd.stream_args(
-        		cpu_format="fc32",
-        		channels=range(1),
-        	),
-        )
+        self.uhd_usrp_sink = uhd.usrp_sink(options.args, uhd.io_type_t.COMPLEX_FLOAT32, 1)
         self.uhd_usrp_sink.set_samp_rate(options.sample_rate)
         self.uhd_usrp_sink.set_center_freq(options.frequency, 0)
         self.uhd_usrp_sink.set_gain(options.gain, 0)
+        self.uhd_usrp_sink.set_clock_source(options.clock_source)
 
         if options.bits == 16:
             # a file source for the file generated by the gps-sdr-sim
@@ -55,7 +50,13 @@ class top_block(gr.top_block):
             self.connect((self.blocks_file_source, 0), (self.blocks_char_to_short, 0))
             self.connect((self.blocks_char_to_short, 0), (self.blocks_interleaved_short_to_complex, 0))
 
-        self.connect((self.blocks_interleaved_short_to_complex, 0), (self.uhd_usrp_sink, 0))
+        # scale complex values to within +/- 1.0 so don't overflow USRP DAC
+        # scale of 1.0/2**11 will scale it to +/- 0.5
+        self.blocks_multiply_const = blocks.multiply_const_vcc((1.0/2**11, ))
+
+        # establish the connections
+        self.connect((self.blocks_interleaved_short_to_complex, 0), (self.blocks_multiply_const, 0))
+        self.connect((self.blocks_multiply_const, 0), (self.uhd_usrp_sink, 0))
 
 def get_options():
     parser = OptionParser(option_class=eng_option)
@@ -71,6 +72,11 @@ def get_options():
                       help="set output file name [default=gpssim.bin]")
     parser.add_option("-b", "--bits", type="eng_float", default=16,
                       help="set size of every sample [default=16]")
+    parser.add_option("-a", "--args", type="string", default="",
+                      help="set UHD arguments [default='']")
+    parser.add_option("-c", "--clock_source", type="string", default="internal",
+                      help="set clock source [default='internal']")
+
 
     (options, args) = parser.parse_args()
     if len(args) != 0: