OLED 0.96

缘起

自从使用Raspberry Pi Pico以后，就觉得MicroPython真的太方便了。各种应用想实现就分分钟搞定。
这里面不得不说OLED屏幕中0.96inch的存在，真是小巧又可爱。
在刷新OLED的屏幕时，常用到ssd1306的库，那都是底层，最重要的还是使用framebuf库的功能。
其中，我最喜欢就是用bytearray去做为输入的buf。
例如我就常常：

from machine import Pin, ADC, I2C
from time import sleep
import framebuf
from ssd1306 import SSD1306_I2C

WIDTH = 128
HEIGHT = 64

buf = bytearray(b'') # 这里定义buf。 后面讲这里的buf怎么实现。

fb = framebuf.FrameBuffer(buf, framebuf.MONO_VLSB)

bus = I2C(1, scl=Pin(15), sda=Pin(14), freq=2000000)
oled = SSD1306_I2C(WIDTH, HEIGHT, bus)

while True:
    oled.fill(0)
    oled.show()
    sleep(0.01)
    oled.blit(fb, 0, 0) 
    oled.show()
    sleep(0.5)

buf的实现方法

1. 打开windows的绘图板，生成一个128x64的画布
   然后自己随便画个图像并保存。
2. 然后打开pycharm编写如下代码：

from io import BytesIO
from PIL import Image
import sys

if len(sys.argv) > 1:
    path_to_image = str(sys.argv[1])
    x = int(sys.argv[2])
    y = int(sys.argv[3])
    im = Image.open(path_to_image).convert('1')
    im_resize = im.resize((x,y))
    buf = BytesIO()
    im_resize.save(buf, 'ppm')
    byte_im = buf.getvalue()
    temp = len(str(x) + ' ' + str(y)) + 4
    print(byte_im[temp::])
else:
    print("please specify the location of image i.e img2bytearray.py /path/to/image width heigh")

然后执行这个代码并提供图片的位置，这样就将图片生成了一段bytearray数组，拷贝到buf的位置。

红框部分的内容复制到bytearray的位置。上传到pico，就搞定了。
非常简单。

树莓派4B + ESC (Hobbywing) + SKYwalker 2212 无刷电机

测试步骤

0. 搭建电路
   
1. 校准电调
2. 驱动电机ESC.py 测试代码:

# This program will let you test your ESC and brushless motor.
# Make sure your battery is not connected if you are going to calibrate it at first.
# Since you are testing your motor, I hope you don't have your propeller attached to it otherwise you are in trouble my friend...?
# This program is made by AGT @instructable.com. DO NOT REPUBLISH THIS PROGRAM... actually the program itself is harmful                                             pssst Its not, its safe.

import os     #importing os library so as to communicate with the system
import time   #importing time library to make Rpi wait because its too impatient 
os.system ("sudo pigpiod") #Launching GPIO library
time.sleep(1) # As i said it is too impatient and so if this delay is removed you will get an error
import pigpio #importing GPIO library

ESC=4  #Connect the ESC in this GPIO pin 

pi = pigpio.pi();
pi.set_servo_pulsewidth(ESC, 0) 

max_value = 2000 #change this if your ESC's max value is different or leave it be
min_value = 700  #change this if your ESC's min value is different or leave it be
print "For first time launch, select calibrate"
print "Type the exact word for the function you want"
print "calibrate OR manual OR control OR arm OR stop"

def manual_drive(): #You will use this function to program your ESC if required
    print "You have selected manual option so give a value between 0 and you max value"    
    while True:
        inp = raw_input()
        if inp == "stop":
            stop()
            break
        elif inp == "control":
            control()
            break
        elif inp == "arm":
            arm()
            break   
        else:
            pi.set_servo_pulsewidth(ESC,inp)

def calibrate():   #This is the auto calibration procedure of a normal ESC
    pi.set_servo_pulsewidth(ESC, 0)
    print("Disconnect the battery and press Enter")
    inp = raw_input()
    if inp == '':
        pi.set_servo_pulsewidth(ESC, max_value)
        print("Connect the battery NOW.. you will here two beeps, then wait for a gradual falling tone then press Enter")
        inp = raw_input()
        if inp == '':            
            pi.set_servo_pulsewidth(ESC, min_value)
            print "Wierd eh! Special tone"
            time.sleep(7)
            print "Wait for it ...."
            time.sleep (5)
            print "Im working on it, DONT WORRY JUST WAIT....."
            pi.set_servo_pulsewidth(ESC, 0)
            time.sleep(2)
            print "Arming ESC now..."
            pi.set_servo_pulsewidth(ESC, min_value)
            time.sleep(1)
            print "See.... uhhhhh"
            control() # You can change this to any other function you want

def control(): 
    print "I'm Starting the motor, I hope its calibrated and armed, if not restart by giving 'x'"
    time.sleep(1)
    speed = 1500    # change your speed if you want to.... it should be between 700 - 2000
    print "Controls - a to decrease speed & d to increase speed OR q to decrease a lot of speed & e to increase a lot of speed"
    while True:
        pi.set_servo_pulsewidth(ESC, speed)
        inp = raw_input()

        if inp == "q":
            speed -= 100    # decrementing the speed like hell
            print "speed = %d" % speed
        elif inp == "e":    
            speed += 100    # incrementing the speed like hell
            print "speed = %d" % speed
        elif inp == "d":
            speed += 10     # incrementing the speed 
            print "speed = %d" % speed
        elif inp == "a":
            speed -= 10     # decrementing the speed
            print "speed = %d" % speed
        elif inp == "stop":
            stop()          #going for the stop function
            break
        elif inp == "manual":
            manual_drive()
            break
        elif inp == "arm":
            arm()
            break   
        else:
            print "WHAT DID I SAID!! Press a,q,d or e"

def arm(): #This is the arming procedure of an ESC 
    print "Connect the battery and press Enter"
    inp = raw_input()    
    if inp == '':
        pi.set_servo_pulsewidth(ESC, 0)
        time.sleep(1)
        pi.set_servo_pulsewidth(ESC, max_value)
        time.sleep(1)
        pi.set_servo_pulsewidth(ESC, min_value)
        time.sleep(1)
        control() 

def stop(): #This will stop every action your Pi is performing for ESC ofcourse.
    pi.set_servo_pulsewidth(ESC, 0)
    pi.stop()

#This is the start of the program actually, to start the function it needs to be initialized before calling... stupid python.    
inp = raw_input()
if inp == "manual":
    manual_drive()
elif inp == "calibrate":
    calibrate()
elif inp == "arm":
    arm()
elif inp == "control":
    control()
elif inp == "stop":
    stop()
else :
    print "Thank You for not following the things I'm saying... now you gotta restart the program STUPID!!"

起因

今天 rockets 问我, 是否能够将二维码里面的色块用 0 和 1 表示出来.

分析

我脑海里分析了一下,不知道是不是可以用 opencv 实现,就打开电脑尝试了一下,似乎是可以的.
思路, 首先通过 qrcode 生成一个图片,然后保存一下,通过opencv 导入图片,然后再判断 10x10 大小的块中是否全是白色,如果是白色,就写一个 1
,如果是黑色,就写个 0. 然后遍历整个图片的 shape.

Talk is cheap, show me the code

import qrcode
import cv2
import numpy as np

url = 'https://www.dfrobot.com/product-2480.html'
file_name = 'qrcode.png'

def generate_image(url):
    qr = qrcode.QRCode()
    qr.add_data(url)
    qr.make(fit=False)
    img = qr.make_image(fill_color="black", back_color="white")
    img.save(file_name)

generate_image(url)
img1 = cv2.imread(file_name)
scale_percent = 80
width = int(img1.shape[1] * scale_percent / 100)
height = int(img1.shape[0] * scale_percent / 100)
dim = (width, height)

resized_img = cv2.resize(img1, dim, interpolation=cv2.INTER_AREA)
# gray_img1 = cv2.cvtColor(img1, cv2.COLOR_BGR2GRAY)
for i in range(0, int(resized_img.shape[0]), 10):
    for j in range(0, int(resized_img.shape[1]), 10):
        if np.mean(resized_img[i:i+10, j:j+10]) == 255:
            cv2.putText(resized_img, '0', (i, j), cv2.FONT_HERSHEY_SIMPLEX, .2, (255, 0, 0))
        else:
            cv2.putText(resized_img, '1', (i, j), cv2.FONT_HERSHEY_SIMPLEX, .2, (255, 0, 0))

cv2.imshow('resized_img', resized_img)
cv2.waitKey(0)

执行效果:

重点

np.mean(图片数组) == 255的判断部分,可以判断图片是不是白色.

重构了一下,优化后:

import qrcode
import cv2
import numpy as np

# 定义生成 qrcode 的 url 链接和生成的文件名
url = 'https://www.dfrobot.com/product-2480.html'
file_name = 'qrcode.png'

def generate_image(url):
    """"
    生成二维码并保存
    """
    qr = qrcode.QRCode()
    qr.add_data(url)
    qr.make(fit=False)
    img = qr.make_image(fill_color="black", back_color="white")
    img.save(file_name)

def process_image(filename):
    """
    :param filename: 放入生成的二维码
    :return: 显示图
    """
    img1 = cv2.imread(file_name)
    scale_percent = 80
    width = int(img1.shape[1] * scale_percent / 100)
    height = int(img1.shape[0] * scale_percent / 100)
    dim = (width, height)
    resized_img = cv2.resize(img1, dim, interpolation=cv2.INTER_AREA)
    for i in range(0, int(resized_img.shape[0]), 10):
        for j in range(0, int(resized_img.shape[1]), 10):
            if np.mean(resized_img[i:i+5, j:j+5]) == 255:
                cv2.putText(resized_img, '0', (i+5, j+5), cv2.FONT_HERSHEY_SIMPLEX, .2, (255, 0, 0))
            else:
                cv2.putText(resized_img, '1', (i+5, j+5), cv2.FONT_HERSHEY_SIMPLEX, .2, (255, 0, 0))

    cv2.imshow('resized_img', resized_img)
    cv2.waitKey(0)

if __name__ == "__main__":
    generate_image(url)
    process_image(file_name)

优化后结果:

感觉还是不太对.

继续优化试试看.

import qrcode
import cv2
import numpy as np

# 定义生成 qrcode 的 url 链接和生成的文件名
url = 'https://www.dfrobot.com/product-2480.html'
file_name = 'qrcode.png'

def generate_image(url):
    """"
    生成二维码并保存
    """
    qr = qrcode.QRCode()
    qr.add_data(url)
    qr.make(fit=False)
    img = qr.make_image(fill_color="black", back_color="white")
    img.save(file_name)

def process_image(filename):
    """
    :param filename: 放入生成的二维码
    :return: 显示图
    """
    img1 = cv2.imread(file_name)
    scale_percent = 200
    width = int(img1.shape[1] * scale_percent / 100)
    height = int(img1.shape[0] * scale_percent / 100)
    dim = (width, height)
    resized_img = cv2.resize(img1, dim, interpolation=cv2.INTER_AREA)
    resized_img = cv2.cvtColor(resized_img, cv2.COLOR_BGR2GRAY)
    for i in range(0, int(resized_img.shape[0]), 10):
        for j in range(0, int(resized_img.shape[1]), 10):
            if np.mean(resized_img[i:i+3, j:j+3]) == 255:
                cv2.putText(resized_img, '1', (i + 5, j + 5), cv2.FONT_HERSHEY_SIMPLEX, .2, (0, 0, 255))
            else:
                cv2.putText(resized_img, '0', (i + 5, j + 5), cv2.FONT_HERSHEY_SIMPLEX, .2, (255, 0, 0))

    cv2.imshow('img', resized_img)
    cv2.waitKey(0)

if __name__ == "__main__":
    generate_image(url)
    process_image(file_name)

输出结果:

今天实现了对物体检测并控制舵机运动的应用。
舵机使用了pca9685控制，因此备份一下pac9685舵机控制板的驱动：

PCA9685.py

import time
import math

class PWM:
    _mode_adr      = 0x00
    _base_adr_low  = 0x08
    _base_adr_high = 0x09
    _prescale_adr  = 0xFE

    def __init__(self, bus, address = 0x40):
        '''
        Creates an instance of the PWM chip at given i2c address.
        @param bus: the SMBus instance to access the i2c port(0 or 1).
        @param address: the address of the i2c chip (default: 0x40).
        '''
        self.bus = bus
        self.address = address
        self._writeByte(self._mode_adr, 0x00)

    def setFreq(self, freq):
        '''
        Sets the PWM frequency. The value is stored in the device.
        @param freq: the frequency in Hz (approx.)
        '''
        prescaleValue = 25000000.0  # 25MHz
        prescaleValue /= 4096.0     # 12-bit
        prescaleValue /= float(freq)
        prescaleValue -= 1.0  
        prescale = math.floor(prescaleValue + 0.5)
        oldmode = self._readByte(self._mode_adr)
        if oldmode == None:
            return
        newmode = (oldmode & 0x7F) | 0x10
        self._writeByte(self._mode_adr, newmode)
        self._writeByte(self._prescale_adr, int(math.floor(prescale)))
        self._writeByte(self._mode_adr, oldmode)
        time.sleep(0.005)
        self._writeByte(self._mode_adr, oldmode | 0x80)

    def setDuty(self, channel, duty):
        '''
        Sets a single PWM channel. The value is stored in the device.
        @param channel: one of the channels 0..15
        @param duty: the duty cycle 0..100
        '''
        data = int(duty * 4096 /100)  # 0..4096 (included)
        self._writeByte(self._base_adr_low + 4 * channel, data & 0xFF)
        self._writeByte(self._base_adr_high + 4 * channel, data >> 8)

    def _writeByte(self, reg, value):
        try:
            self.bus.write_byte_data(self.address, reg, value)
        except:
            print("Error while writing to I2C device")

    def _readByte(self, reg):
        try:
            result = self.bus.read_byte_data(self.address, reg)
            return result
        except:
            print("Error while Reading from I2C device")
            return None

调用方法简单：

import time
from smbus2 import SMBus
from pca9685 import PWM

freq = 50
addr = 0x40
channels = [0, 1, 2] 
a = 12.5
b = 2

bus = SMBus(1)
pwm = PWM(bus, addr)
pwm.setFreq(freq)

def setPos(channel, pos):
    duty = a / 180 * pos + b 
    pwm.setDuty(channel, duty)
    time.sleep(0.1)

while True:
    try:
        for pos in range(60, 120, 2):
            setPos(channels[0], pos)
            time.sleep(0.1)

        for pos in range(60, 120, 3):
            setPos(channels[1], pos)
            time.sleep(0.5)

        for pos in range(0, 90, 3):
            setPos(channels[2], pos)
            time.sleep(0.01)

    except KeyboardInterrupt:
        for i in channels:
            setPos(i, 0)
        break

OpenCV 通过颜色检测并控制：

import cv2
import time
import numpy as np
from pca9685 import PWM
from smbus2 import SMBus

freq = 50
addr = 0x40
ch1  = 0
ch2  = 1

bus = SMBus(1)
pwm = PWM(bus, addr)
pwm.setFreq(freq)

def setPos(channel, position):
    pwm.setDuty(channel, position)
    time.sleep(0.01)

def posMap(x, in_min, in_max, out_min, out_max):
    return int((x - in_min) * (out_max - out_min) / (in_max - in_min) + out_min)

cap = cv2.VideoCapture(0)
cap.set(3, 320)
cap.set(4, 160)
ret, frame = cap.read()

cx = int(frame.shape[1] / 2)
center = int(frame.shape[1] / 2)
pos = 90

while True:
    ret, frame = cap.read()
    frame = cv2.flip(frame, 1)
    hsv_frame = cv2.cvtColor(frame, cv2.COLOR_BGR2HSV)
    ly = np.array([51, 0, 0])
    hy = np.array([180, 255, 255])

    mask = cv2.inRange(hsv_frame, ly, hy)
    contours, hir = cv2.findContours(mask, cv2.RETR_TREE, cv2.CHAIN_APPROX_SIMPLE)
    contours = sorted(contours, key=lambda x: cv2.contourArea(x), reverse=True)
    # cv2.drawContours(frame, contours[1], -1, (0, 0, 255), 2)
    for cnt in contours[1:]:
        (x, y, w, h) = cv2.boundingRect(cnt)
        cv2.rectangle(frame, (x, y), (x+w, y+h), (255, 255,0), 2)
        cx = int((x + x + w)/ 2)
        # cv2.drawContours(frame, cnt, -1, (0, 0, 255), 2)
        cv2.line(frame, (cx, 0), (cx, frame.shape[0]), (0, 0, 255), 1)
        if cx < center:
            pos -= 1.5
        elif cx > center:
            pos += 1.5  
        # pos = posMap(pos, 1, 480, 60, 120)
        setPos(ch1, pos)

        break
    # mask = cv2.cvtColor(mask, cv2.COLOR_GRAY2BGR)
    # hstack = np.hstack([mask, frame])
    cv2.imshow('frame', frame)
    if cv2.waitKey(1) & 0xFF == 27:
        break

cap.release()
cv2.destroyAllWindows()
setPos(ch1, 0)

总结

就是控制dutyCycle，频率肯定要50hz，一般的多级可能需要a， b函数作为微调。根据自己的舵机微调a和b的值。

可以尝试 a 设置8.5， b设置2