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Merged
NejcKle merged 1 commit into from
Mar 6, 2023
Merged

Modify multiprocessing to accept chunk size in seconds #22

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12 changes: 8 additions & 4 deletions example.py
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Original file line number Diff line number Diff line change
Expand Up @@ -19,8 +19,10 @@

ppk2_test = PPK2_API(ppk2_port)
ppk2_test.get_modifiers()
ppk2_test.use_ampere_meter() # set ampere meter mode
ppk2_test.toggle_DUT_power("OFF") # disable DUT power
ppk2_test.set_source_voltage(3300)

ppk2_test.use_source_meter() # set source meter mode
ppk2_test.toggle_DUT_power("ON") # enable DUT power

ppk2_test.start_measuring() # start measuring
# measurements are a constant stream of bytes
Expand All @@ -34,14 +36,16 @@
print(f"Average of {len(samples)} samples is: {sum(samples)/len(samples)}uA")
time.sleep(0.01)

ppk2_test.toggle_DUT_power("ON")
ppk2_test.toggle_DUT_power("OFF") # disable DUT power

ppk2_test.use_ampere_meter() # set ampere meter mode

ppk2_test.start_measuring()
for i in range(0, 1000):
read_data = ppk2_test.get_data()
if read_data != b'':
samples = ppk2_test.get_samples(read_data)
print(f"Average of {len(samples)} samples is: {sum(samples)/len(samples)}uA")
time.sleep(0.001) # lower time between sampling -> less samples read in one sampling period
time.sleep(0.01) # lower time between sampling -> less samples read in one sampling period

ppk2_test.stop_measuring()
36 changes: 19 additions & 17 deletions example_mp.py
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Original file line number Diff line number Diff line change
@@ -1,49 +1,51 @@

"""
Basic usage of PPK2 Python API - multiprocessing version
Basic usage of PPK2 Python API - multiprocessing version.
The basic ampere mode sequence is:
1. read modifiers
2. set ampere mode
3. read stream of data
"""
import time
from ppk2_api.ppk2_api import PPK2_MP
from ppk2_api.ppk2_api import PPK2_MP as PPK2_API

ppk2s_connected = PPK2_MP.list_devices()
ppk2s_connected = PPK2_API.list_devices()
if(len(ppk2s_connected) == 1):
ppk2_port = ppk2s_connected[0]
print(f'Found PPK2 at {ppk2_port}')
else:
print(f'Too many connected PPK2\'s: {ppk2s_connected}')
exit()

ppk2_test = PPK2_MP(ppk2_port)
ppk2_test = PPK2_API(ppk2_port, buffer_max_size_seconds=1, buffer_chunk_seconds=0.01)
ppk2_test.get_modifiers()
ppk2_test.use_ampere_meter() # set ampere meter mode
ppk2_test.toggle_DUT_power("OFF") # disable DUT power
ppk2_test.set_source_voltage(3300)

ppk2_test.start_measuring() # start measuring
ppk2_test.use_source_meter() # set source meter mode
ppk2_test.toggle_DUT_power("ON") # enable DUT power

ppk2_test.start_measuring() # start measuring
# measurements are a constant stream of bytes
# multiprocessing variant starts a process in the background which constantly
# polls the device in order to prevent losing samples. It will buffer the
# last 10s (by default) of data so get_data() can be called less frequently.
for i in range(0, 10):
# the number of measurements in one sampling period depends on the wait between serial reads
# it appears the maximum number of bytes received is 1024
# the sampling rate of the PPK2 is 100 samples per millisecond
for i in range(0, 1000):
read_data = ppk2_test.get_data()
if read_data != b'':
samples = ppk2_test.get_samples(read_data)
print(f"Average of {len(samples)} samples is: {sum(samples)/len(samples)}uA")
time.sleep(0.5)
time.sleep(0.001)

ppk2_test.toggle_DUT_power("ON")
ppk2_test.toggle_DUT_power("OFF") # disable DUT power

ppk2_test.use_ampere_meter() # set ampere meter mode

ppk2_test.start_measuring()
for i in range(0, 10):
for i in range(0, 1000):
read_data = ppk2_test.get_data()
if read_data != b'':
samples = ppk2_test.get_samples(read_data)
print(f"Average of {len(samples)} samples is: {sum(samples)/len(samples)}uA")
time.sleep(0.5) # lower time between sampling -> less samples read in one sampling period

ppk2_test.stop_measuring()
time.sleep(0.001) # lower time between sampling -> less samples read in one sampling period

ppk2_test.stop_measuring()
15 changes: 9 additions & 6 deletions src/ppk2_api/ppk2_api.py
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Original file line number Diff line number Diff line change
Expand Up @@ -397,7 +397,7 @@ def run(self):
self._buffer_q.get()
local_buffer = local_buffer[self._buffer_chunk:]
self._last_timestamp = tm_now
#print(len(d), len(local_buffer), self._buffer_q.qsize())
# print(len(d), len(local_buffer), self._buffer_q.qsize())

# calculate stats
s += len(d)
Expand All @@ -423,7 +423,7 @@ def get_data(self):
count = 0
while True:
try:
ret += self._buffer_q.get(timeout=0.01) # get_nowait sometimes skips a chunk for some reason
ret += self._buffer_q.get(timeout=0.001) # get_nowait sometimes skips a chunk for some reason
count += 1
except queue.Empty:
break
Expand All @@ -435,15 +435,18 @@ class PPK2_MP(PPK2_API):
Multiprocessing variant of the object. The interface is the same as for the regular one except it spawns
a background process on start_measuring()
'''
def __init__(self, port, buffer_seconds=10):
def __init__(self, port, buffer_max_size_seconds=10, buffer_chunk_seconds=0.1):
'''
port - port where PPK2 is connected
buffer_seconds - how many seconds of data to keep in the buffer
buffer_max_size_seconds - how many seconds of data to keep in the buffer
buffer_chunk_seconds - how many seconds of data to put in the queue at once
'''
super().__init__(port)

self._fetcher = None
self._quit_evt = multiprocessing.Event()
self._buffer_seconds = buffer_seconds
self._buffer_max_size_seconds = buffer_max_size_seconds
self._buffer_chunk_seconds = buffer_chunk_seconds

def __del__(self):
"""Destructor"""
Expand All @@ -467,7 +470,7 @@ def start_measuring(self):
if self._fetcher is not None:
return

self._fetcher = PPK_Fetch(self, self._quit_evt, self._buffer_seconds)
self._fetcher = PPK_Fetch(self, self._quit_evt, self._buffer_max_size_seconds, self._buffer_chunk_seconds)
self._fetcher.start()

def stop_measuring(self):
Expand Down