Question

我正在使用Raspberry Pi 3和ADS1115，我的项目要求我获得均匀间隔的样本，以便进行绘图和分析。其他帖子是关于实现10k和50k sps，但我只需要500SPS，这也不起作用。有没有办法用500 sps运行我的代码120秒，同时从A0和A1通道获得60,000个样本？我附上了代码供参考。提前致谢

from Adafruit_ADS1x15 import ADS1x15
import time
import numpy as np

pga = 2/3                  # Set full-scale range of programmable gain  
                            # amplifier (page 13 of data sheet), change 
                            #depending on the input voltage range
ADS1115 = 0x01              # Specify that the device being used is the 
                            #  ADS1115, for the ADS1015 used 0x00
adc = Adafruit_ADS1x15.ADS1015()   # Create instance of the class ADS1x15

# Function to print sampled values to the terminal
def logdata():

    print "sps value should be one of: 8, 16, 32, 64, 128, 250, 475, 860, 
    otherwise the value will default to 250"

    frequency = input("Input sampling frequency (Hz):     ")    # Get 
                                               #sampling frequency from user
    sps = input("Input sps (Hz) :     ")                        # Get 
                                           # ads1115 sps value from the user
    time1 = input("Input sample time (seconds):     ")          # Get how 
                                           #long to sample for from the user

    period = 1.0 / frequency        # Calculate sampling period

    datapoints = int(time1*frequency)       # Datapoints is the total number 
                               #of samples to take, which must be an integer

    startTime=time.time()                   # Time of first sample
    t1=startTime                            # T1 is last sample time
    t2=t1                                   # T2 is current time

    for x in range (0,datapoints) :     # Loop in which data is sampled

            while (t2-t1 < period) :        # Check if t2-t1 is less then 
                                     #sample period, if it is then update t2
                t2=time.time()              # and check again       
            t1+=period                      # Update last sample time by the 
                                            #  sampling period

            print adc.read_adc(0, pga, data_rate=sps), "mV      ", ("%.2f" % 
(t2-startTime)) , "s"      # Print sampled value and time to the terminal

# Call to logdata function
logdata()

Answer 1

1）您是否正在使用ADS1115？

adc = Adafruit_ADS1x15.ADS1015()   # should be adc = Adafruit_ADS1x15.ADS1115()

2）您不能同时读取两个或多个单端通道。在差分模式下，可以比较两个通道以产生一个值。要从通道1读取值，除了通道0外，您还必须在循环中添加另一个调用：

print adc.read_adc(0, pga, data_rate=sps) ..... # original call for channel 0
print adc.read_adc(1, pga, data_rate=sps) ..... # new call for channel 1

3）在读取值之前，必须为ADS配置多个参数，例如通道，速率，增益等。经过一段时间后（进行模/数转换），可以读取一次值，或在连续模式下一遍又一遍。在原始的ADAFruit library中，这次是根据数据速率（不安全）计算的，而在最近的端口中，CircuitPython这次通常是在0.01 s左右，因为转换很可能不会直接完成配置后（检查_read method）。

4）以500SPS的读取速度是ADS1115可以读取的最快速度。 reference指出，以860SPS进行转换需要1.2毫秒。花费时间进行配置和读取，即使您收到转换通知（如我在homepage上所述），也不必等待固定的时间，您将无法每0.002s连续读取两个或多个值。时间。

5）我认为，使用Python可以得到的最接近的结果是，以连续模式通过GPIO通知运行2个菊花链式ADS1115，但我对此没有经验。

使用Sample count或time.time（）在RasPi3和ADS1115中进行采样

1 个答案: