MicroPython内核开发笔记书内软件用例 ：I2C部分的实验

简 介： 本文给出了 MicroPython内核开发笔记：书内嵌入实验任务 中的 I2C 件用例部分内容。

关键词： MM32F3277，MicroPython，SofiI2C，I2C

• 本书稿内容隶属于 MicroPython内核开发笔记：书内嵌入实验任务 中的内容。

软件用例：
这部分书稿内容包括有：
1.
2.

• 书稿内位置：

§01 书稿内容

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一、基础实验

1、SoftI2C初始化

下面代码给出了初始化一个 SoftI2C 总线接口的过程，通过 print ，dir 两个命令观察 SoftI2C 总线的属性以及提供接口函数。

from machine                import Pin,I2C,SoftI2C

scl = Pin('PA0')
sda = Pin('PA1')

i2c = SoftI2C(scl, sda, freq=100000)

print(i2c)
dir(i2c)

上述代码运行结果为：

SoftI2C(scl=PA0, sda=PA1, freq=100000)
['readinto', 'start', 'stop', 'write', 'init', 'readfrom', 'readfrom_into', 'readfrom_mem', 'readfrom_mem_into', 'scan', 'writeto', 'writeto_mem', 'writevto']
>>> 

一个 SoftI2C 对象提供了以下接口函数：

• tart ： 产生 I2C 起始状态信号；
• top ： 产生 I2C 停止状态信号；
• can：扫错 I2C 总线上设备；
• readfrom，readfrom_into，readfrom_mem, readfrom_memo_into：从外部设备读入字节；
• writeto，writevto，writeto_mem：将字节写入接收设备；

2、观察SoftI2C信号

（1）扫描器件波形

下面代码利用 PC6，PC7 作为 SoftI2C 的 SCL，SDA信号。 重复执行 i2c.scan() 命令。使用示波器测量 SCL，SDA 信号波形。

from machine                import Pin,I2C,SoftI2C
import time

scl = Pin('PC6')
sda = Pin('PC7')

i2c = SoftI2C(scl, sda, freq=100000)

while True:
    i2c.scan()
    time.sleep_ms(20)

示波器抓取到的 SCL，SDA 信号波形如下。 可以看到 I2C 中的 scan 函数，执行对 I2C 总线所有可能的地址进行扫描，获得有响应器件的地址。

▲ 图1.1.1 SCL,SDA信号波形

在 PLUS-F3270 实验板上包含有两个 I2C 器件，一个是MPU6050，另外一个是 K24C02。MPU6050对应的 I2C 地址为 0x68，K24C02对于的 I2C 地址为 0x50。

▲ 图1.1.2 PLUS-F3270实验板上的两个I2C器件

使用 I2C 的 scan 函数，得到的结果为： [80, 104]，分别是K24C02， MPU6050 的 I2C 地址。

3、读写 K24C02

下面代码将 0 ~ 7 八个字节写入 K24C02 前八个字节。

from machine                import Pin,SoftI2C
import time

scl = Pin('PC6')
sda = Pin('PC7')

i2c = SoftI2C(scl, sda, freq=100000)

buf = bytes((0x0,0,1,2,3,4,5,6,7))
i2c.writeto(0x50, buf)
time.sleep_ms(10)

下面重新读取前八个字节。前两个语句实际上执行一个空写指令，是为了设置 EEPROM 当前的地址指针。然后连续读取 0x10 数字显示出来。

buf = bytes((0x0,))
i2c.writeto(0x50, buf)

buf = i2c.readfrom(0x50, 0x20)
print(buf)

执行结果为：

1
b'\x00\x01\x02\x03\x04\x05\x06\x07\xff\xff\xff\xff\xff\xff\xff\xff\x00\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff'

第一数字 1 是 i2c.writeto 执行后，返回实际 I2C 总线传输字节个数。 后面 16 个字节数字，前八个是前面写入的数字，后面八个仍然保持为 0xff 。

二、操作I2C接口OLED

1、两线接口OLED

OLED显示屏是常用的设备输出器件，它通常具有两种接口：

• 七线接口： 除了电源（VDD，GND）之外，还有时钟（SCK）、数据（SDA），复位（RES），功能（DC）以及片选（CS）信号；
• 四线接口： 除了电源（VDD,GND）之外，包括I2C总结两个接口SCK， SDA。

▲ 图1.2.1 128×64 OLED液晶显示屏 左：期限接口OLED；右：四线接口OLED

四线接口，实际上就是 I2C 总线接口。下面将 I2C 总结接口的 OLED 连接到 简易实验板的 PA0，PA1 两个管脚上。

▲ 图1.2.2 在面包板上将两线OLED与简易实验板连接

2、扫描OLED地址

使用 I2C 的 scan 函数测试 OLED的 I2C 地址。

from machine                import Pin,SoftI2C
import utime

print("Test I2C")

scl = Pin('PA0')
sda = Pin('PA1')

i2c = SoftI2C(scl, sda, freq=100000)

ret = i2c.scan()
print(ret)

程序运行结果为：

Test I2C
[60]

3、液晶初始化

下面给出了对于 OLED 进行初始化的代码，这个代码将 OLED平面显示为白色。

from machine                import Pin,SoftI2C
import utime
from micropython import const
#------------------------------------------------------------
scl = Pin('PA0')
sda = Pin('PA1')
i2c = SoftI2C(scl, sda, freq=100000)
#------------------------------------------------------------
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
        self.buffer = bytearray(self.pages * self.width)
        self.init_display()
    def init_display(self):
        for cmd in (
            SET_DISP | 0x00,            # off
            SET_MEM_ADDR, 0x00,         # horizontal
            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,
            SET_DISP_CLK_DIV, 0x80,
            SET_PRECHARGE, 0x22 if self.external_vcc else 0xf1,
            SET_VCOM_DESEL, 0x30,       # 0.83*Vcc
            SET_CONTRAST, 0xff,         # maximum
            SET_ENTIRE_ON,              # output follows RAM contents
            SET_NORM_INV,               # not inverted
            SET_CHARGE_PUMP, 0x10 if self.external_vcc else 0x14,
            SET_DISP | 0x01):           # on
            self.write_cmd(cmd)
        self.fill(0xff)
        self.show()
    def fill(self, c):
        for i in range(len(self.buffer)):
            self.buffer[i] = c
    def poweroff(self):
        self.write_cmd(SET_DISP | 0x00)
    def poweron(self):
        self.write_cmd(SET_DISP | 0x01)
    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:
            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_data(self.buffer)
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)
        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_data(self, buf):
        self.temp[0] = self.addr << 1
        self.temp[1] = 0x40         # Co=0, D/C#=1
        self.i2c.start()
        self.i2c.write(self.temp)
        self.i2c.write(buf)
        self.i2c.stop()
#------------------------------------------------------------
oled = SSD1306_I2C(128, 64, i2c, addr=0x3c)

下面动图显示了 OLED 被初始化的放慢的过程。

▲ 图1.2.3 SoftI2C初始化OLED

4、显示字符信息

下面代码给出了在 OLED上显示字符的示例程序。

from machine                import Pin,SoftI2C
import utime
from micropython import const

scl = Pin('PA0')
sda = Pin('PA1')

i2c = SoftI2C(scl, sda, freq=400000)

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)

font8x16 = bytes((0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,
  0x00,0x00,0x00,0xF8,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x33,0x30,0x00,0x00,0x00,
  0x00,0x10,0x0C,0x06,0x10,0x0C,0x06,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,
  0x40,0xC0,0x78,0x40,0xC0,0x78,0x40,0x00,0x04,0x3F,0x04,0x04,0x3F,0x04,0x04,0x00,
  0x00,0x70,0x88,0xFC,0x08,0x30,0x00,0x00,0x00,0x18,0x20,0xFF,0x21,0x1E,0x00,0x00,
  0xF0,0x08,0xF0,0x00,0xE0,0x18,0x00,0x00,0x00,0x21,0x1C,0x03,0x1E,0x21,0x1E,0x00,
  0x00,0xF0,0x08,0x88,0x70,0x00,0x00,0x00,0x1E,0x21,0x23,0x24,0x19,0x27,0x21,0x10,
  0x10,0x16,0x0E,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,
  0x00,0x00,0x00,0xE0,0x18,0x04,0x02,0x00,0x00,0x00,0x00,0x07,0x18,0x20,0x40,0x00,
  0x00,0x02,0x04,0x18,0xE0,0x00,0x00,0x00,0x00,0x40,0x20,0x18,0x07,0x00,0x00,0x00,
  0x40,0x40,0x80,0xF0,0x80,0x40,0x40,0x00,0x02,0x02,0x01,0x0F,0x01,0x02,0x02,0x00,
  0x00,0x00,0x00,0xF0,0x00,0x00,0x00,0x00,0x01,0x01,0x01,0x1F,0x01,0x01,0x01,0x00,
  0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x80,0xB0,0x70,0x00,0x00,0x00,0x00,0x00,
  0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x01,0x01,0x01,0x01,0x01,0x01,0x01,
  0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x30,0x30,0x00,0x00,0x00,0x00,0x00,
  0x00,0x00,0x00,0x00,0x80,0x60,0x18,0x04,0x00,0x60,0x18,0x06,0x01,0x00,0x00,0x00,
  0x00,0xE0,0x10,0x08,0x08,0x10,0xE0,0x00,0x00,0x0F,0x10,0x20,0x20,0x10,0x0F,0x00,
  0x00,0x10,0x10,0xF8,0x00,0x00,0x00,0x00,0x00,0x20,0x20,0x3F,0x20,0x20,0x00,0x00,
  0x00,0x70,0x08,0x08,0x08,0x88,0x70,0x00,0x00,0x30,0x28,0x24,0x22,0x21,0x30,0x00,
  0x00,0x30,0x08,0x88,0x88,0x48,0x30,0x00,0x00,0x18,0x20,0x20,0x20,0x11,0x0E,0x00,
  0x00,0x00,0xC0,0x20,0x10,0xF8,0x00,0x00,0x00,0x07,0x04,0x24,0x24,0x3F,0x24,0x00,
  0x00,0xF8,0x08,0x88,0x88,0x08,0x08,0x00,0x00,0x19,0x21,0x20,0x20,0x11,0x0E,0x00,
  0x00,0xE0,0x10,0x88,0x88,0x18,0x00,0x00,0x00,0x0F,0x11,0x20,0x20,0x11,0x0E,0x00,
  0x00,0x38,0x08,0x08,0xC8,0x38,0x08,0x00,0x00,0x00,0x00,0x3F,0x00,0x00,0x00,0x00,
  0x00,0x70,0x88,0x08,0x08,0x88,0x70,0x00,0x00,0x1C,0x22,0x21,0x21,0x22,0x1C,0x00,
  0x00,0xE0,0x10,0x08,0x08,0x10,0xE0,0x00,0x00,0x00,0x31,0x22,0x22,0x11,0x0F,0x00,
  0x00,0x00,0x00,0xC0,0xC0,0x00,0x00,0x00,0x00,0x00,0x00,0x30,0x30,0x00,0x00,0x00,
  0x00,0x00,0x00,0x80,0x00,0x00,0x00,0x00,0x00,0x00,0x80,0x60,0x00,0x00,0x00,0x00,
  0x00,0x00,0x80,0x40,0x20,0x10,0x08,0x00,0x00,0x01,0x02,0x04,0x08,0x10,0x20,0x00,
  0x40,0x40,0x40,0x40,0x40,0x40,0x40,0x00,0x04,0x04,0x04,0x04,0x04,0x04,0x04,0x00,
  0x00,0x08,0x10,0x20,0x40,0x80,0x00,0x00,0x00,0x20,0x10,0x08,0x04,0x02,0x01,0x00,
  0x00,0x70,0x48,0x08,0x08,0x08,0xF0,0x00,0x00,0x00,0x00,0x30,0x36,0x01,0x00,0x00,
  0xC0,0x30,0xC8,0x28,0xE8,0x10,0xE0,0x00,0x07,0x18,0x27,0x24,0x23,0x14,0x0B,0x00,
  0x00,0x00,0xC0,0x38,0xE0,0x00,0x00,0x00,0x20,0x3C,0x23,0x02,0x02,0x27,0x38,0x20,
  0x08,0xF8,0x88,0x88,0x88,0x70,0x00,0x00,0x20,0x3F,0x20,0x20,0x20,0x11,0x0E,0x00,
  0xC0,0x30,0x08,0x08,0x08,0x08,0x38,0x00,0x07,0x18,0x20,0x20,0x20,0x10,0x08,0x00,
  0x08,0xF8,0x08,0x08,0x08,0x10,0xE0,0x00,0x20,0x3F,0x20,0x20,0x20,0x10,0x0F,0x00,
  0x08,0xF8,0x88,0x88,0xE8,0x08,0x10,0x00,0x20,0x3F,0x20,0x20,0x23,0x20,0x18,0x00,
  0x08,0xF8,0x88,0x88,0xE8,0x08,0x10,0x00,0x20,0x3F,0x20,0x00,0x03,0x00,0x00,0x00,
  0xC0,0x30,0x08,0x08,0x08,0x38,0x00,0x00,0x07,0x18,0x20,0x20,0x22,0x1E,0x02,0x00,
  0x08,0xF8,0x08,0x00,0x00,0x08,0xF8,0x08,0x20,0x3F,0x21,0x01,0x01,0x21,0x3F,0x20,
  0x00,0x08,0x08,0xF8,0x08,0x08,0x00,0x00,0x00,0x20,0x20,0x3F,0x20,0x20,0x00,0x00,
  0x00,0x00,0x08,0x08,0xF8,0x08,0x08,0x00,0xC0,0x80,0x80,0x80,0x7F,0x00,0x00,0x00,
  0x08,0xF8,0x88,0xC0,0x28,0x18,0x08,0x00,0x20,0x3F,0x20,0x01,0x26,0x38,0x20,0x00,
  0x08,0xF8,0x08,0x00,0x00,0x00,0x00,0x00,0x20,0x3F,0x20,0x20,0x20,0x20,0x30,0x00,
  0x08,0xF8,0xF8,0x00,0xF8,0xF8,0x08,0x00,0x20,0x3F,0x00,0x3F,0x00,0x3F,0x20,0x00,
  0x08,0xF8,0x30,0xC0,0x00,0x08,0xF8,0x08,0x20,0x3F,0x20,0x00,0x07,0x18,0x3F,0x00,
  0xE0,0x10,0x08,0x08,0x08,0x10,0xE0,0x00,0x0F,0x10,0x20,0x20,0x20,0x10,0x0F,0x00,
  0x08,0xF8,0x08,0x08,0x08,0x08,0xF0,0x00,0x20,0x3F,0x21,0x01,0x01,0x01,0x00,0x00,
  0xE0,0x10,0x08,0x08,0x08,0x10,0xE0,0x00,0x0F,0x18,0x24,0x24,0x38,0x50,0x4F,0x00,
  0x08,0xF8,0x88,0x88,0x88,0x88,0x70,0x00,0x20,0x3F,0x20,0x00,0x03,0x0C,0x30,0x20,
  0x00,0x70,0x88,0x08,0x08,0x08,0x38,0x00,0x00,0x38,0x20,0x21,0x21,0x22,0x1C,0x00,
  0x18,0x08,0x08,0xF8,0x08,0x08,0x18,0x00,0x00,0x00,0x20,0x3F,0x20,0x00,0x00,0x00,
  0x08,0xF8,0x08,0x00,0x00,0x08,0xF8,0x08,0x00,0x1F,0x20,0x20,0x20,0x20,0x1F,0x00,
  0x08,0x78,0x88,0x00,0x00,0xC8,0x38,0x08,0x00,0x00,0x07,0x38,0x0E,0x01,0x00,0x00,
  0xF8,0x08,0x00,0xF8,0x00,0x08,0xF8,0x00,0x03,0x3C,0x07,0x00,0x07,0x3C,0x03,0x00,
  0x08,0x18,0x68,0x80,0x80,0x68,0x18,0x08,0x20,0x30,0x2C,0x03,0x03,0x2C,0x30,0x20,
  0x08,0x38,0xC8,0x00,0xC8,0x38,0x08,0x00,0x00,0x00,0x20,0x3F,0x20,0x00,0x00,0x00,
  0x10,0x08,0x08,0x08,0xC8,0x38,0x08,0x00,0x20,0x38,0x26,0x21,0x20,0x20,0x18,0x00,
  0x00,0x00,0x00,0xFE,0x02,0x02,0x02,0x00,0x00,0x00,0x00,0x7F,0x40,0x40,0x40,0x00,
  0x00,0x0C,0x30,0xC0,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x01,0x06,0x38,0xC0,0x00,
  0x00,0x02,0x02,0x02,0xFE,0x00,0x00,0x00,0x00,0x40,0x40,0x40,0x7F,0x00,0x00,0x00,
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  0x00,0x00,0x80,0x80,0x80,0x80,0x00,0x00,0x00,0x1F,0x22,0x22,0x22,0x22,0x13,0x00,
  0x00,0x80,0x80,0xF0,0x88,0x88,0x88,0x18,0x00,0x20,0x20,0x3F,0x20,0x20,0x00,0x00,
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  0x08,0xF8,0x00,0x00,0x80,0x80,0x80,0x00,0x20,0x3F,0x24,0x02,0x2D,0x30,0x20,0x00,
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  0x80,0x80,0x00,0x80,0x80,0x80,0x00,0x00,0x20,0x3F,0x21,0x00,0x00,0x20,0x3F,0x20,
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  0x00,0x00,0x00,0x80,0x80,0x80,0x80,0x00,0x00,0x0E,0x11,0x20,0x20,0xA0,0xFF,0x80,
  0x80,0x80,0x80,0x00,0x80,0x80,0x80,0x00,0x20,0x20,0x3F,0x21,0x20,0x00,0x01,0x00,
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  0x00,0x80,0x80,0xE0,0x80,0x80,0x00,0x00,0x00,0x00,0x00,0x1F,0x20,0x20,0x00,0x00,
  0x80,0x80,0x00,0x00,0x00,0x80,0x80,0x00,0x00,0x1F,0x20,0x20,0x20,0x10,0x3F,0x20,
  0x80,0x80,0x80,0x00,0x00,0x80,0x80,0x80,0x00,0x01,0x0E,0x30,0x08,0x06,0x01,0x00,
  0x80,0x80,0x00,0x80,0x00,0x80,0x80,0x80,0x0F,0x30,0x0C,0x03,0x0C,0x30,0x0F,0x00,
  0x00,0x80,0x80,0x00,0x80,0x80,0x80,0x00,0x00,0x20,0x31,0x2E,0x0E,0x31,0x20,0x00,
  0x80,0x80,0x80,0x00,0x00,0x80,0x80,0x80,0x80,0x81,0x8E,0x70,0x18,0x06,0x01,0x00,
  0x00,0x80,0x80,0x80,0x80,0x80,0x80,0x00,0x00,0x21,0x30,0x2C,0x22,0x21,0x30,0x00,
  0x00,0x00,0x00,0x00,0x80,0x7C,0x02,0x02,0x00,0x00,0x00,0x00,0x00,0x3F,0x40,0x40,
  0x00,0x00,0x00,0x00,0xFF,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0xFF,0x00,0x00,0x00,
  0x00,0x02,0x02,0x7C,0x80,0x00,0x00,0x00,0x00,0x40,0x40,0x3F,0x00,0x00,0x00,0x00,
  0x00,0x06,0x01,0x01,0x02,0x02,0x04,0x04,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00))

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
        self.buffer = bytearray(self.pages * self.width)
        self.init_display()

    def init_display(self):
        for cmd in (
            SET_DISP | 0x00,            # off
            SET_MEM_ADDR, 0x00,         # horizontal
            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,
            SET_DISP_CLK_DIV, 0x80,
            SET_PRECHARGE, 0x22 if self.external_vcc else 0xf1,
            SET_VCOM_DESEL, 0x30,       # 0.83*Vcc
            SET_CONTRAST, 0xff,         # maximum
            SET_ENTIRE_ON,              # output follows RAM contents
            SET_NORM_INV,               # not inverted
            SET_CHARGE_PUMP, 0x10 if self.external_vcc else 0x14,
            SET_DISP | 0x01):           # on
            self.write_cmd(cmd)
        self.fill(0x0)
        self.show()

    def fill(self, c):
        for i in range(len(self.buffer)):
            self.buffer[i] = c

    def poweroff(self):
        self.write_cmd(SET_DISP | 0x00)

    def poweron(self):
        self.write_cmd(SET_DISP | 0x01)

    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:
            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_data(self.buffer)

    def setpoint(self, x,y):
        liney = y//8
        yy = 1<<(y%8)
        self.buffer[liney*self.width+x] |= yy

    def setstring(self, x,y,str):
        for c in str:
            cid = ord(c) - 0x20
            cid *= 16
            for i in range(8):
                ii = y*self.width+x*8+i
                self.buffer[ii] = font8x16[cid+i]
                self.buffer[ii+self.width] = font8x16[cid+i+8]

            x += 1
            if x >= self.width//8:
                x = 0
                y += 1

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)
        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_data(self, buf):
        self.temp[0] = self.addr << 1
        self.temp[1] = 0x40         # Co=0, D/C#=1
        self.i2c.start()
        self.i2c.write(self.temp)
        self.i2c.write(buf)
        self.i2c.stop()

oled = SSD1306_I2C(128, 64, i2c, addr=0x3c)

oled.setstring(0, 0, '  MM32F3277')
oled.setstring(0, 2, 'MicroPython:V2')
oled.show()

count = 0
while True:
    oled.setstring(3, 6, 'Count:%04d'%count)
    count += 1
    oled.show()

    utime.sleep_ms(100)

▲ 图1 利用 SoftI2C 控制OLED显示字符信息

※ 总  结 ※

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本文给出了 MicroPython内核开发笔记：书内嵌入实验任务 中的 I2C 件用例部分内容。

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■ 相关文献链接:

• MicroPython内核开发笔记：书内嵌入实验任务

● 相关图表链接:

• 图1.1.1 SCL,SDA信号波形
• 图1.1.2 PLUS-F3270实验板上的两个I2C器件
• 图1.2.2 在面包板上将两线OLED与简易实验板连接
• 图1.2.3 SoftI2C初始化OLED
• 图1 利用 SoftI2C 控制OLED显示字符信息