【树莓派 PICO 2 测评】采集 DS18B20 数据及 OLED 显示

本文介绍了树莓派 PICO 2 采集 DS18B20 数据以及 OLED 显示环境温度信息。

硬件连接

OLED_SCL -> GPIO5

OLED_SDA -> GPIO4

DS18B20 -> GPIO6

DS18B20模块详见：DS18B20模块 - 立创开源硬件平台

DS18B20

串口打印 DS18B20 传感器数据

代码

import machine, onewire, ds18x20, time
ds_pin = machine.Pin(4) # 定义 ds18x20 传感器数据引脚
ow = onewire.OneWire(ds_pin)# 使能单总线
ds = ds18x20.DS18X20(ow) # 传感器为 DS18x20
roms = ds.scan() # 扫描单总线上的传感器地址，支持多个传感器同时连接
print('Found DS18x20 devices: ', roms)
​
while True:
    ds.convert_temp() # 温度采集转换
    time.sleep_ms(750) # 初始化延时，以获取正确读数
    
    for rom in roms:
        temp = ds.read_temp(roms[0]) # 温度显示, rom[0] 为第 1 个 DS18B20
        print("{:.2f}".format(temp)) # 打印温度数值，保留两位小数
    time.sleep(1)

效果

IIC OLED

添加 ssd1306.py 至树莓派 Pico 2 根目录

# MicroPython SSD1306 OLED driver, I2C and SPI interfaces created by Adafruit
​
import time
import framebuf
​
# register definitions
SET_CONTRAST        = const(0x81)
SET_ENTIRE_ON       = const(0xa4)
SET_NORM_INV        = const(0xa6)
SET_DISP            = const(0xae)
SET_MEM_ADDR        = const(0x20)
SET_COL_ADDR        = const(0x21)
SET_PAGE_ADDR       = const(0x22)
SET_DISP_START_LINE = const(0x40)
SET_SEG_REMAP       = const(0xa0)
SET_MUX_RATIO       = const(0xa8)
SET_COM_OUT_DIR     = const(0xc0)
SET_DISP_OFFSET     = const(0xd3)
SET_COM_PIN_CFG     = const(0xda)
SET_DISP_CLK_DIV    = const(0xd5)
SET_PRECHARGE       = const(0xd9)
SET_VCOM_DESEL      = const(0xdb)
SET_CHARGE_PUMP     = const(0x8d)
​
​
class SSD1306:
    def __init__(self, width, height, external_vcc):
        self.width = width
        self.height = height
        self.external_vcc = external_vcc
        self.pages = self.height // 8
        # Note the subclass must initialize self.framebuf to a framebuffer.
        # This is necessary because the underlying data buffer is different
        # between I2C and SPI implementations (I2C needs an extra byte).
        self.poweron()
        self.init_display()
​
    def init_display(self):
        for cmd in (
            SET_DISP | 0x00, # off
            # address setting
            SET_MEM_ADDR, 0x00, # horizontal
            # resolution and layout
            SET_DISP_START_LINE | 0x00,
            SET_SEG_REMAP | 0x01, # column addr 127 mapped to SEG0
            SET_MUX_RATIO, self.height - 1,
            SET_COM_OUT_DIR | 0x08, # scan from COM[N] to COM0
            SET_DISP_OFFSET, 0x00,
            SET_COM_PIN_CFG, 0x02 if self.height == 32 else 0x12,
            # timing and driving scheme
            SET_DISP_CLK_DIV, 0x80,
            SET_PRECHARGE, 0x22 if self.external_vcc else 0xf1,
            SET_VCOM_DESEL, 0x30, # 0.83*Vcc
            # display
            SET_CONTRAST, 0xff, # maximum
            SET_ENTIRE_ON, # output follows RAM contents
            SET_NORM_INV, # not inverted
            # charge pump
            SET_CHARGE_PUMP, 0x10 if self.external_vcc else 0x14,
            SET_DISP | 0x01): # on
            self.write_cmd(cmd)
        self.fill(0)
        self.show()
​
    def poweroff(self):
        self.write_cmd(SET_DISP | 0x00)
​
    def contrast(self, contrast):
        self.write_cmd(SET_CONTRAST)
        self.write_cmd(contrast)
​
    def invert(self, invert):
        self.write_cmd(SET_NORM_INV | (invert & 1))
​
    def show(self):
        x0 = 0
        x1 = self.width - 1
        if self.width == 64:
            # displays with width of 64 pixels are shifted by 32
            x0 += 32
            x1 += 32
        self.write_cmd(SET_COL_ADDR)
        self.write_cmd(x0)
        self.write_cmd(x1)
        self.write_cmd(SET_PAGE_ADDR)
        self.write_cmd(0)
        self.write_cmd(self.pages - 1)
        self.write_framebuf()
​
    def fill(self, col):
        self.framebuf.fill(col)
​
    def pixel(self, x, y, col):
        self.framebuf.pixel(x, y, col)
​
    def scroll(self, dx, dy):
        self.framebuf.scroll(dx, dy)
​
    def text(self, string, x, y, col=1):
        self.framebuf.text(string, x, y, col)
​
​
class SSD1306_I2C(SSD1306):
    def __init__(self, width, height, i2c, addr=0x3c, external_vcc=False):
        self.i2c = i2c
        self.addr = addr
        self.temp = bytearray(2)
        # Add an extra byte to the data buffer to hold an I2C data/command byte
        # to use hardware-compatible I2C transactions.  A memoryview of the
        # buffer is used to mask this byte from the framebuffer operations
        # (without a major memory hit as memoryview doesn't copy to a separate
        # buffer).
        self.buffer = bytearray(((height // 8) * width) + 1)
        self.buffer[0] = 0x40  # Set first byte of data buffer to Co=0, D/C=1
        self.framebuf = framebuf.FrameBuffer1(memoryview(self.buffer)[1:], width, height)
        super().__init__(width, height, external_vcc)
​
    def write_cmd(self, cmd):
        self.temp[0] = 0x80 # Co=1, D/C#=0
        self.temp[1] = cmd
        self.i2c.writeto(self.addr, self.temp)
​
    def write_framebuf(self):
        # Blast out the frame buffer using a single I2C transaction to support
        # hardware I2C interfaces.
        self.i2c.writeto(self.addr, self.buffer)
​
    def poweron(self):
        pass
​
​
class SSD1306_SPI(SSD1306):
    def __init__(self, width, height, spi, dc, res, cs, external_vcc=False):
        self.rate = 10 * 1024 * 1024
        dc.init(dc.OUT, value=0)
        res.init(res.OUT, value=0)
        cs.init(cs.OUT, value=1)
        self.spi = spi
        self.dc = dc
        self.res = res
        self.cs = cs
        self.buffer = bytearray((height // 8) * width)
        self.framebuf = framebuf.FrameBuffer1(self.buffer, width, height)
        super().__init__(width, height, external_vcc)
​
    def write_cmd(self, cmd):
        self.spi.init(baudrate=self.rate, polarity=0, phase=0)
        self.cs.high()
        self.dc.low()
        self.cs.low()
        self.spi.write(bytearray([cmd]))
        self.cs.high()
​
    def write_framebuf(self):
        self.spi.init(baudrate=self.rate, polarity=0, phase=0)
        self.cs.high()
        self.dc.high()
        self.cs.low()
        self.spi.write(self.buffer)
        self.cs.high()
​
    def poweron(self):
        self.res.high()
        time.sleep_ms(1)
        self.res.low()
        time.sleep_ms(10)
        self.res.high()
​

Thonny IDE 新建文件，粘贴该库代码，文件 - 另存为 - Raspberry Pi Pico - 命名为 ssd1306.py - OK .

详见：Random Nerd Tutorials .

设备扫描

调用 ssd1306 库文件实现 IIC 设备扫描

代码

# I2C Scanner MicroPython
from machine import Pin, SoftI2C
​
# You can choose any other combination of I2C pins
i2c = SoftI2C(scl=Pin(5), sda=Pin(4))
​
print('I2C SCANNER')
devices = i2c.scan()
​
if len(devices) == 0:
  print("No i2c device !")
else:
  print('i2c devices found:', len(devices))
​
  for device in devices:
    print("I2C hexadecimal address: ", hex(device))

效果

文字显示

调用 ssd1306 库文件实现 IIC OLED 设备连接并显示文本

代码

from machine import Pin, SoftI2C
import ssd1306
​
#You can choose any other combination of I2C pins
i2c = SoftI2C(scl=Pin(5), sda=Pin(4))
​
oled_width = 128
oled_height = 64
oled = ssd1306.SSD1306_I2C(oled_width, oled_height, i2c)
​
oled.text('Hello, World 1!', 0, 0)
oled.text('Hello, World 2!', 0, 10)
oled.text('Hello, World 3!', 0, 20)
​
oled.show()

效果

传感器显示

结合前面关于 DS18B20 温度传感器的测试，将温度数据显示在 OLED 屏幕上

代码

import machine, onewire, ds18x20, time
from machine import Pin, SoftI2C
import ssd1306
​
# initialize oled
i2c = SoftI2C(scl=Pin(5), sda=Pin(4))   # initialize IIC: scl--> 5, sda --> 4
oled_width = 128
oled_height = 64
oled = ssd1306.SSD1306_I2C(oled_width, oled_height, i2c)
 
# initialize DS18B20
ow= onewire.OneWire(Pin(6))   # 使能单总线
ds = ds18x20.DS18X20(ow)        # 传感器 DS18B20
rom = ds.scan()         # 扫描单总线上的传感器地址，支持多个传感器同时连接
 
while True:
     
    ds.convert_temp()   # 温度采集转换
    temp = ds.read_temp(rom[0]) # 温度显示, rom[0] 为第 1 个 DS18B20
    #temp_str = str(round(temp, 2)) # 保留两位小数
    temp_str = str('%.2f'%temp) # 保留两位小数
    print(temp_str)
 
    # Show data
    oled.fill(0)   # 清屏背景黑色
    oled.text('DS18B20', 0, 0)
    oled.text('Temperature:',0,20)
    oled.text(temp_str +' C',0,40) # 显示 temp
    oled.show()
 
    time.sleep_ms(1000)

效果

同时 Shell 打印温度值

总结

本文介绍了树莓派 PICO 2 采集 DS18B20 数据以及 OLED 显示环境温度信息，从 SSD1306 驱动库文件开始，实现 IIC 设备扫描、OLED 文字显示、DS18B20 传感器读取、传感器数据的 OLED 显示。为 IIC 驱动的相关硬件开发与传感器的应用提供了参考。