236 lines
9.2 KiB
Python
236 lines
9.2 KiB
Python
#!/usr/bin/python
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# -*- coding: utf-8 -*-
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"""PiPyADC: Example file for class ADS1256 in module pipyadc:
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ADS1256 cycling through eight input channels.
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Default data rate changed to 100 SPS. Check if hardware is connected.
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Moving average filter over 32 samples.
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Reading ADC sample data directly into a Numpy array as a buffer
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for further processing, e.g. FIR filter, PID control, ...
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Hardware: Waveshare ADS1256 board interfaced to the Raspberry Pi 3
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Ulrich Lukas 2017-03-10
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"""
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import sys,os
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sys.path.append('/opt/bienen/PiPyADC')
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import time
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import numpy as np
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import itertools
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from ADS1256_definitions import *
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from pipyadc import ADS1256
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# In this example, we pretend myconfig_2 was a different configuration file
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# named "myconfig_2.py" for a second ADS1256 chip connected to the SPI bus.
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import ADS1256_tim01_config as myconfig_2
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grafanaurl="%GRAFANA_URL%"
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first=True
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### START EXAMPLE ###
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################################################################################
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### STEP 0: CONFIGURE CHANNELS AND USE DEFAULT OPTIONS FROM CONFIG FILE: ###
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#
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# For channel code values (bitmask) definitions, see ADS1256_definitions.py.
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# The values representing the negative and positive input pins connected to
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# the ADS1256 hardware multiplexer must be bitwise OR-ed to form eight-bit
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# values, which will later be sent to the ADS1256 MUX register. The register
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# can be explicitly read and set via ADS1256.mux property, but here we define
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# a list of differential channels to be input to the ADS1256.read_sequence()
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# method which reads all of them one after another.
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#
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# ==> Each channel in this context represents a differential pair of physical
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# input pins of the ADS1256 input multiplexer.
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#
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# ==> For single-ended measurements, simply select AINCOM as the negative input.
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#
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# AINCOM does not have to be connected to AGND (0V), but it is if the jumper
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# on the Waveshare board is set.
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#
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# Input pin for the potentiometer on the Waveshare Precision ADC board:
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POTI = POS_AIN0|NEG_AINCOM
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# Light dependant resistor of the same board:
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LDR = POS_AIN1|NEG_AINCOM
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# The other external input screw terminals of the Waveshare board:
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EXT2, EXT3, EXT4 = POS_AIN2|NEG_AINCOM, POS_AIN3|NEG_AIN4, POS_AIN4|NEG_AIN3
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EXT5, EXT6, EXT7 = POS_AIN5|NEG_AINCOM, POS_AIN6|NEG_AINCOM, POS_AIN7|NEG_AINCOM
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# You can connect any pin as well to the positive as to the negative ADC input.
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# The following reads the voltage of the potentiometer with negative polarity.
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# The ADC reading should be identical to that of the POTI channel, but negative.
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POTI_INVERTED = POS_AINCOM|NEG_AIN0
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# For fun, connect both ADC inputs to the same physical input pin.
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# The ADC should always read a value close to zero for this.
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SHORT_CIRCUIT = POS_AIN0|NEG_AIN0
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# Specify here an arbitrary length list (tuple) of arbitrary input channel pair
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# eight-bit code values to scan sequentially from index 0 to last.
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# Eight channels fit on the screen nicely for this example..
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#CH_SEQUENCE = (POTI, LDR, EXT2, EXT3, EXT4, EXT7, POTI_INVERTED, SHORT_CIRCUIT)
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CH_SEQUENCE = (EXT3,)
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################################################################################
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########################## CALIBRATION CONSTANTS ############################
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# This shows how to use individual channel calibration values.
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#
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# The ADS1256 has internal gain and offset calibration registers, but these are
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# applied to all channels without making any difference.
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# I we want to use individual calibration values, e.g. to compensate external
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# circuitry parasitics, we can do this very easily in software.
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# The following values are only for demonstration and have no meaning.
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CH_OFFSET = np.array((-10, 0, -85, 0, 750, 0, 0, 0), dtype=np.int)
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GAIN_CAL = np.array((1.0, 1.0, 1.0, 1.0, 1.0, 1.0, 1.0, 1.0), dtype=np.float)
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################################################################################
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# Using the Numpy library, digital signal processing is easy as (Raspberry) Pi..
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# However, this constant only specifies the length of a moving average.
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FILTER_SIZE = 2
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################################################################################
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def do_measurement():
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### STEP 1: Initialise ADC objects for two chips connected to the SPI bus.
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# In this example, we pretend myconfig_2 was a different configuration file
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# named "myconfig_2.py" for a second ADS1256 chip connected to the SPI bus.
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# This file must be imported, see top of the this file.
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# Omitting the first chip here, as this is only an example.
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#ads1 = ADS1256(myconfig_1)
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# (Note1: See ADS1256_default_config.py, see ADS1256 datasheet)
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# (Note2: Input buffer on means limited voltage range 0V...3V for 5V supply)
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ads2 = ADS1256(myconfig_2)
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# Just as an example: Change the default sample rate of the ADS1256:
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# This shows how to acces ADS1256 registers via instance property
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ads2.drate = DRATE_2_5
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ads2.pga_gain = 64
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#ads2.mux = POS_AIN4 | NEG_AIN3
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### STEP 2: Gain and offset self-calibration:
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ads2.cal_self()
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### Get ADC chip ID and check if chip is connected correctly.
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chip_ID = ads2.chip_ID
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print("\nADC No. 2 reported a numeric ID value of: {}.".format(chip_ID))
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# When the value is not correct, user code should exit here.
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if chip_ID != 3:
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print("\nRead incorrect chip ID for ADS1256. Is the hardware connected?")
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# Passing that step because this is an example:
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# sys.exit(1)
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# Channel gain must be multiplied by LSB weight in volts per digit to
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# display each channels input voltage. The result is a np.array again here:
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CH_GAIN = ads2.v_per_digit * GAIN_CAL
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# Numpy 2D array as buffer for raw input samples. Each row is one complete
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# sequence of samples for eight input channel pin pairs. Each column stores
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# the number of FILTER_SIZE samples for each channel.
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rows, columns = FILTER_SIZE, len(CH_SEQUENCE)
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filter_buffer = np.zeros((rows, columns), dtype=np.int)
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# Fill the buffer first once before displaying continuously updated results
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print("Channels configured: {}\n"
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"Initializing filter (this can take a minute)...".format(
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len(CH_SEQUENCE)))
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for row_number, data_row in enumerate(filter_buffer):
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# Do the data acquisition of eight multiplexed input channels.
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# The ADS1256 read_sequence() method automatically fills into
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# the buffer specified as the second argument:
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ads2.read_sequence(CH_SEQUENCE, data_row)
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# Depending on aquisition speed and filter lenth, this can take long...
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sys.stdout.write(
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"\rProgress: {:3d}%".format(int(100*(row_number+1)/FILTER_SIZE)))
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sys.stdout.flush()
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# From now, update filter_buffer cyclically with new ADC samples and
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# calculate results with averaged results.
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print("\n\nOutput values averaged over {} ADC samples:".format(FILTER_SIZE))
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# The following is an endless loop!
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timestamp = time.time() # Limit output data rate to fixed time interval
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for data_row in itertools.cycle(filter_buffer):
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#
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# Do the data acquisition of eight multiplexed input channels
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#
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# The result channel values are directy read into the array specified
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# as the second argument, which must be a mutable type.
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ads2.read_sequence(CH_SEQUENCE, data_row)
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elapsed = time.time() - timestamp
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if elapsed > .1:
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timestamp += .1
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# Calculate moving average of input samples, subtract offset
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ch_unscaled = np.average(filter_buffer, axis=0) - CH_OFFSET
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ch_volts = ch_unscaled * CH_GAIN
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to_grafana([int(i) for i in ch_unscaled], ch_volts)
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### END EXAMPLE ###
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#############################################################################
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# Format nice looking text output:
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def nice_output(digits, volts):
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sys.stdout.write(
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"\0337" # Store cursor position
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+
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"""These are the raw sample values for the channels:
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Poti_CH0, LDR_CH1, AIN2, AIN3, AIN4, AIN7, Poti NEG, Short 0V
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"""
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+ ", ".join(["{: 8d}".format(i) for i in digits])
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+
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"""
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These are the sample values converted to voltage in V for the channels:
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Poti_CH0, LDR_CH1, AIN2, AIN3, AIN4, AIN7, Poti NEG, Short 0V
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"""
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+ ", ".join(["{: 8.3f}".format(i) for i in volts])
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+ "\n\033[J\0338" # Restore cursor position etc.
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)
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def tim_nice_output(digits, volts):
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global first
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global res0
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res=float(85.5+64000*volts[0:1])
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if first:
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res0=res
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res=res-res0
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first=False
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sys.stdout.write(
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"\0337" # Store cursor position
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+ "{: 8.4f}".format(res)
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+ "\n\033[J\0338" # Restore cursor position etc.
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)
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def to_grafana(digits, volts):
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global first
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global res0
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res=float(85.5+5/7.5*6400*volts[0:1])
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sys.stdout.write(
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"\0337" # Store cursor position
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+ "{: 8.4f}".format(res)
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+ "\n\033[J\0338" # Restore cursor position etc.
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)
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try:
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os.system("curl -i -XPOST '"+grafanaurl+"' --data-binary 'weight,location=bees01 value="+str(res)+"'")
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except:
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print("no access to grafana?")
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pass
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time.sleep(5)
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# Start data acquisition
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try:
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print("\033[2J\033[H") # Clear screen
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print(__doc__)
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print("\nPress CTRL-C to exit.")
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do_measurement()
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except (KeyboardInterrupt):
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print("\n"*8 + "User exit.\n")
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