""" QTRSensors.h - Originally Arduino Library for using Pololu QTR reflectance sensors and reflectance sensor arrays MIT Licence Copyright (c) 2008-2012 waveshare Corporation. For more information, see https://www.waveshare.com/wiki/AlphaBot2-Ar Copyright (c) 2021 leomlr (Léo Meillier). For more information, see https://github.com/vittascience/stm32-libraries https://vittascience.com/stm32/ You may freely modify and share this code, as long as you keep this notice intact. Disclaimer: To the extent permitted by law, waveshare provides this work without any warranty. It might be defective, in which case you agree to be responsible for all resulting costs and damages. Author: Léo Meillier (leomlr) Date: 07/2021 Note: library adapted in micropython for using 5 QTR sensors on Alphabot v2 robot controlled by STM32 board. """ import pyb from micropython import const import utime PIN_CS = 'D10' PIN_DOUT = 'D11' PIN_ADDR = 'D12' PIN_CLK = 'D13' NUMSENSORS = const(5) QTR_EMITTERS_OFF = const(0x00) QTR_EMITTERS_ON = const(0x01) QTR_EMITTERS_ON_AND_OFF = const(0x02) QTR_NO_EMITTER_PIN = const(0xff) QTR_MAX_SENSORS = const(16) class TRSensors(object): """ Base class data member initialization (called by derived class init()). """ def __init__(self, cs=PIN_CS, dout=PIN_DOUT, addr=PIN_ADDR, clk=PIN_CLK): self._cs = pyb.Pin(cs, pyb.Pin.OUT) self._dout = pyb.Pin(dout, pyb.Pin.IN) self._addr = pyb.Pin(addr, pyb.Pin.OUT) self._clk = pyb.Pin(clk, pyb.Pin.OUT) self._numSensors = NUMSENSORS self.calibratedMin = [0] * self._numSensors self.calibratedMax = [1023] * self._numSensors self.last_value = 0 """ Reads the sensor values using TLC1543 ADC chip into an array. The values returned are a measure of the reflectance in abstract units, with higher values corresponding to lower reflectance (e.g. a black surface or a void). """ def analogRead(self): value = [0]* (self._numSensors+1) #Read Channel0~channel4 AD value for j in range(0, self._numSensors+1): self._cs.off() for i in range(0,4): #sent 4-bit Address if (j >> (3 - i)) & 0x01: self._addr.on() else: self._addr.off() #read MSB 4-bit data value[j] <<= 1 if self._dout.value(): value[j] |= 0x01 self._clk.on() self._clk.off() for i in range(0, self._numSensors+1): #read LSB 8-bit data value[j] <<= 1 if self._dout.value(): value[j] |= 0x01 self._clk.on() self._clk.off() #no mean ,just delay #for i in range(0,6): # self._clk.on() # self._clk.off() utime.sleep_us(100) self._cs.on() return value[1:] """ Reads the sensors 10 times and uses the results for calibration. The sensor values are not returned instead, the maximum and minimum values found over time are stored internally and used for the readCalibrated() method. """ def calibrate(self): sensor_values = [] max_sensor_values = [0]*self._numSensors min_sensor_values = [0]*self._numSensors for j in range(0, 10): sensor_values = self.analogRead() for i in range(0, self._numSensors): # set the max we found THIS time if j == 0 or max_sensor_values[i] < sensor_values[i]: max_sensor_values[i] = sensor_values[i] # set the min we found THIS time if j == 0 or min_sensor_values[i] > sensor_values[i]: min_sensor_values[i] = sensor_values[i] # record the min and max calibration values for i in range(0, self._numSensors): if min_sensor_values[i] > self.calibratedMax[i]: self.calibratedMax[i] = min_sensor_values[i] if max_sensor_values[i] < self.calibratedMin[i]: self.calibratedMin[i] = max_sensor_values[i] """ Returns values calibrated to a value between 0 and 1000, where 0 corresponds to the minimum value read by calibrate() and 1000 corresponds to the maximum value. Calibration values are stored separately for each sensor, so that differences in the sensors are accounted for automatically. """ def readCalibrated(self): # read the needed values sensor_values = self.analogRead() for i in range(self._numSensors): denominator = self.calibratedMax[i] - self.calibratedMin[i] value = 0 if denominator is not 0: value = (sensor_values[i] - self.calibratedMin[i]) * 1000 / denominator if value < 0: value = 0 elif value > 1000: value = 1000 sensor_values[i] = value return sensor_values """ Operates the same as read calibrated, but also returns an estimated position of the robot with respect to a line. The estimate is made using a weighted average of the sensor indices multiplied by 1000, so that a return value of 0 indicates that the line is directly below sensor 0, a return value of 1000 indicates that the line is directly below sensor 1, 2000 indicates that it's below sensor 2000, etc. Intermediate values indicate that the line is between two sensors. The formula is: 0*value0 + 1000*value1 + 2000*value2 + ... -------------------------------------------- value0 + value1 + value2 + ... By default, this function assumes a dark line (high values) surrounded by white (low values). If your line is light on black, set the optional second argument white_line to true. In this case, each sensor value will be replaced by (1000-value) before the averaging. """ def readLine(self, white_line = 0): sensor_values = self.readCalibrated() avg = 0 sum = 0 on_line = 0 for i in range(0, self._numSensors): value = sensor_values[i] if white_line: value = 1000-value # keep track of whether we see the line at all if value > 200: on_line = 1 # only average in values that are above a noise threshold if value > 50: avg += value * (i * 1000) # this is for the weighted total, sum += value # this is for the denominator if on_line != 1: # If it last read to the left of center, return 0. if self.last_value < (self._numSensors - 1)*1000/2: #print("left") self.last_value = 0 # If it last read to the right of center, return the max. else: #print("right") self.last_value = (self._numSensors - 1)*1000 else: self.last_value = avg/sum return self.last_value,sensor_values;