Drop numpy requirement until it's actually need in the future.

Author: inductivekickback

README.md

@@ -11,7 +11,7 @@ The main features of the **ppk_api** include:
 ### Requirements
 The interface to the PPK requires Nordic's [nRF Command Line Tools](https://www.nordicsemi.com/Software-and-Tools/Development-Tools/nRF-Command-Line-Tools).
 
-Additionally, the excellent [nRF Pynrfjprog](https://www.nordicsemi.com/Software-and-Tools/Development-Tools/nRF-Pynrfjprog) and [numpy](https://numpy.org/) Python modules can be installed from the command line using pip:
+Additionally, the excellent [nRF Pynrfjprog](https://www.nordicsemi.com/Software-and-Tools/Development-Tools/nRF-Pynrfjprog) Python module can be installed from the command line using pip:
 ```
 $ cd ppk_api
 $ pip3 install --user -r requirements.txt

ppk/ppk.py

@@ -5,8 +5,7 @@
 import time
 import struct
 import re
-
-from numpy import average as np_avg
+import math
 
 
 class PPKError(Exception):
@@ -234,7 +233,7 @@ def measure_average(self, time_s, discard_jitter_count=500):
         ts, avg_buf = ppk_helper.get_average_buffs()[0]
         timestamped_buf = [(ts + self.AVERAGE_TIME_US * i, avg_buf[i])
                            for i in range(discard_jitter_count, len(avg_buf))]
-        return (np_avg(avg_buf[discard_jitter_count:]), timestamped_buf)
+        return (self.favg(avg_buf[discard_jitter_count:]), timestamped_buf)
 
     def measure_triggers(self, window_time_us, level_ua, count=1):
         """Collect count trigger buffers."""
@@ -277,7 +276,7 @@ def _measure_triggers(self, count=1):
         for ts, trig_buf in ppk_helper.get_trigger_buffs(*self._resistors):
             timestamped_buf = [(ts + self.ADC_SAMPLING_TIME_US * i, trig_buf[i])
                                for i in range(0, len(trig_buf))]
-            result.append((np_avg(trig_buf), timestamped_buf))
+            result.append((self.favg(trig_buf), timestamped_buf))
         return result
 
     def _enable_ext_trigger_in(self):
@@ -371,6 +370,12 @@ def _log(self, logstring, **kwargs):
         if self.logprint:
             print(logstring, **kwargs)
 
+    @staticmethod
+    def favg(float_seq):
+        """Return the average of a sequence of floats."""
+        sum = math.fsum(float_seq)
+        return sum / len(float_seq)
+
     @staticmethod
     def _parse_metadata(metadata_str):
         """Use a Regular Expression to parse a metadata packet."""

requirements.txt

@@ -1,3 +1 @@
-numpy
 pynrfjprog
-