The new Nordic Semiconductor's Power Profiler Kit II (PPK 2) is very useful for real time measurement of device power consumption. The official nRF Connect Power Profiler tool provides a friendly GUI with real-time data display. However there is no support for automated power monitoring. The puropose of this Python API is to enable automated power monitoring and data logging in Python applications.
The main features of the PPK2 Python API (will) include:
- All nRF Connect Power Profiler GUI functionality - In progress
- Data logging to user selectable format - In progress
- Cross-platform support
Unlike the original Power Profiler Kit, the PPK2 uses Serial to communicate with the computer. No additional modules are required.
At this point in time the library provides the basic API with a basic example showing how to read data and toggle DUT power.
To enable power monitoring in Source mode implement the following sequence:
ppk2_test = PPK2_API("/dev/ttyACM3") # serial port will be different for you
ppk2_test.get_modifiers()
ppk2_test.use_source_meter() # set source meter mode
ppk2_test.set_source_voltage(3300) # set source voltage in mV
ppk2_test.start_measuring() # start measuring
# read measured values in a for loop like this:
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
ppk2_test.stop_measuring()
Regular version will struggle to get all samples. Multiprocessing version spawns another process in the background which polls the device constantly for new samples and holds the last 10 seconds of data (default, configurable) in the buffer so get_data() can be called less frequently.
ppk2_test = PPK2_MP("/dev/ttyACM3") # serial port will be different for you
ppk2_test.get_modifiers()
ppk2_test.use_source_meter() # set source meter mode
ppk2_test.set_source_voltage(3300) # set source voltage in mV
ppk2_test.start_measuring() # start measuring
# read measured values in a for loop like this:
for i in range(0, 10):
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(1) # we can do other stuff while the background process if fetching samples
ppk2_test.stop_measuring()
Default behavior of the PPK2 operating in amperemeter mode implies that power to the DUT is only applied when instructed to do so: when the serial connection to the PPK2 is closed, the power applied to the DUT is cut. Unfortunately, this behavior makes unsuitable the use of the API in a production/test chain where the DUT must be powered at all times, not only when PPK2 actively used.
To circumvent this behavior, a client/server architecture is proposed. Simply start the server when the DUT must be powered, then use the client anytime in the production/test chain to measure current. The server is responsible to configure the PPK2 and serve client requests until the server is closed.
Note that it is possible to always "close" the power path to the DUT, but this require board hardware modification. In order to do this, jump wire the right pad of the R39 resistor to TP29 test point (GND).
It is possible to create an executable of the server by using pyinstaller:
pyinstaller -F server.py
pp2-api-python is licensed under GPL V2 license.
What this means is that you can use this hardware and documentation without paying a royalty and knowing that you'll be able to use your version forever. You are also free to make changes but if you share these changes then you have to do so on the same conditions that you enjoy.
IRNAS is name and mark of Institute IRNAS. You may use these name and terms only to attribute the appropriate entity as required by the Open Licence referred to above. You may not use them in any other way and in particular you may not use them to imply endorsement or authorization of any hardware that you design, make or sell.