This tutorial will introduce you to the libpysmu Python interface software layer to control the ADALM1000 active learning hardware module. Python is a general-purpose, object-oriented interpreted language you can use along with the ALM1000 hardware for countless standalone projects.
These tutorial example programs are written in Python and requires that version 2.7.8 of Python be installed on the user's computer. The programs only import modules generally included with standard Python installation packages. The following files are required do these tutorials:
As in all the ALM activities we use the following terminology when referring to the connections to the ALM1000 connector and configuring the hardware. The green shaded rectangles indicate connections to the M1000 analog I/O connector. The analog I/O channel pins are referred to as CA and CB. When configured to force voltage / measure current -V is added as in CA-V or when configured to force current / measure voltage -I is added as in CA-I. When a channel is configured in the high impedance mode to only measure voltage -H is added as CA-H.
Scope traces are similarly referred to by channel and voltage / current. Such as CA-V , CB-V for the voltage waveforms and CA-I , CB-I for the current waveforms.
The digital I/O channel pins are referred to as D0 through D3. These correspond to the pins labeled PIO 0 – PIO 3 on the ALM1000 board silkscreen.
ADALM1000 hardware module
There is are a few pre-defined python functions that interface to the C++ libsmu library. Contained in the pysmu.py file they provide the high level access functions to configure and control the ALM1000 hardware. The pysmu.py file must be imported or cut and pasted into your python program. The following lists the functions currently implemented:
Must be run first
Returns a list of the devices currently plugged into the computer
devx = Smu()
takes a integer for the device, 0 for first device in list, 1 for second etc.
returns index to that device
Both = devx.devices
takes one of the following strings as input 'A' , 'B' for first device, 'C' , 'D' for second device etc.
returns index to that channel
CHA = devx.channels['A']
CHB = devx.channels['B']
AllChan = Both.get_samples(n_samples):
query device for a list of samples from all channels
n_samples parameter is number of samples
n_samples is of type int
returns list of n samples from all the device's channels
AnalogInA = CHA.get_samples(20) get 20 readings and return them to list variable AnalogInA
CHA.set_mode(mode) or CHB.set_mode(mode):
mode can be one of the following strings:
'V' or 'v' sets channel to source voltage measure current ( SVMI )
'I' or 'I' sets channel to source current measure voltage ( SIMV )
'D' or 'd' set channel to high impedance mode, measure voltage
The following functions control the waveform of the analog output channels (could be CHA or CHB).
value is a floating point number from 0 to 5 representing the DC output voltage for that channel
or value is a floating point number from -0.200 to + 0.200 representing the DC output current for that channel
CHA.sine(value1, value2, periodvalue, delayvalue)
CHA.triangle(value1, value2, periodvalue, delayvalue)
CHA.sawtooth(value1, value2, periodvalue, delayvalue)
CHA.square(value1, value2, periodvalue, delayvalue, dutycyclevalue)
CHA.stairstep(value1, value2, periodvalue, delayvalue)
To better visualize how to specify a waveform look at figure 1 where:
value1 is the first peak value of the waveform, could be the minimum or the maximum peak.
value2 is the second peak value of the waveform, could be the minimum or the maximum peak.
If for example value1 is less than value 2 the apparent phase of the wave is 180 degrees from a wave where value1 is greater than value2.
dutycyclevalue is a fractional number from 0 to 1. dutycyclevalue only applies to the square waveform.
Figure 1 How to build a waveform.
To calculate the period from frequency ( in Hertz ) use the following formula:
periodvalue = SAMPLErate/freqvalue where SAMPLErate is generally fixed at 100,000 SPS
To calculate the delay from the phase ( in degrees ) use the following formula:
delayvalue = periodvalue * phasevalue / 360
Direct control over ADALM1000 functionality can be accomplished using the implemented control transfers, a synchronous and slow communication endpoint accessible regardless of the configuration of the device.
Note that the higher level functions libpysmu implements on top of LIBSMU make use of many of the control transfers to configure device state during normal operation. As such, using these low level control transfers while streaming data may not produce the expected results.
The ALM1000 implements many control transfers, including the following:
M1000 microcontroller pin mappings are described below.
|IO Name||Net Name||Net Description||Pin ID|
|PA0||PIO0||user DIO 0-220Ω||0|
|PA1||PIO1||user DIO 1-220Ω||1|
|PA2||PIO2||user DIO 2-220Ω||2|
|PA3||PIO3||user DIO 3-220Ω||3|
|PA4||PIO0||user DIO 0-470Ω||4|
|PA5||PIO1||user DIO 1-470Ω||5|
|PA6||PIO2||user DIO 2-470Ω||6|
|PA7||PIO3||user DIO 3-470Ω||7|
|PB0||UA11-IN0||50Ω from ChA to 2v5||32|
|PB1||UA11-IN1||50Ω from ChA to GND||33|
|PB2||UA11-IN2||ChA close voltage sense loop||34|
|PB3||UA11-IN3||ChA connect output||35|
|PB5||UB11-IN0||50Ω from ChB to 2v5||37|
|PB6||UB11-IN1||50Ω from ChB to GND||38|
|PB7||UB11-IN2||ChB close voltage sense loop||39|
|PB8||UB11-IN3||ChB connect output||40|
|PB17||PWR_ENABLE||turn on power for analog components||49|
|PB19||SWMODE-A||ChA switch SVMI - SIMV||51|
|PB20||SWMODE-B||ChB switch SVMI - SIMV||52|
devx = Smu()
DevID = devx.serials # device ID for 1st M1000 in list
# set PIO1 high
devx.ctrl_transfer(DevID, 0x40, 0x51, 1, 0, 0, 0, 100)
# set PIO1 low
devx.ctrl_transfer(DevID, 0x40, 0x50, 1, 0, 0, 0, 100)
# get state of PIO0
print devx.ctrl_transfer(DevID, 0xc0, 0x91, 0, 0, 0, 1, 100)
# get state of PIO1
print devx.ctrl_transfer(DevID, 0xc0, 0x91, 1, 0, 0, 1, 100)
# set CHA 2.5 V switch to open
devx.ctrl_transfer(DevID, 0x40, 0x51, 32, 0, 0, 0, 100)
# set CHA GND switch to open
devx.ctrl_transfer(DevID, 0x40, 0x51, 33, 0, 0, 0, 100)
# set CHB 2.5 V switch to open
devx.ctrl_transfer(DevID, 0x40, 0x51, 37, 0, 0, 0, 100)
# set CHB GND switch to open
devx.ctrl_transfer(DevID, 0x40, 0x51, 38, 0, 0, 0, 100)
# open CHA voltage sense loop
devx.ctrl_transfer(DevID, 0x40, 0x51, 34, 0, 0, 0, 100)
# open CHB voltage sense loop
devx.ctrl_transfer(DevID, 0x40, 0x51, 39, 0, 0, 0, 100)
For Further Reading:
Active Learning Interface (for) Circuits (and) Electronics (Python program)
ALICE-SA Spectrum Analyzer (Python program)
ADALM1000 Analog Inputs
ADALM1000 Digital Outputs
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