s3c2440裸机编程-SPI

1 SPI原理#

1.1 spi概念#

SPI是串行外设接口(Serial Peripheral Interface)的缩写。是 Motorola 公司推出的一种同步串行接口技术，是一种高速的，全双工，同步的通信总线。

特点：

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高速、同步、全双工、非差分、总线式
主从机通信模式

优点:

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支持全双工通信（SPI的数据输入和输出线独立，所以允许同时完成数据的输入和输出）
数据传输速率快（I2c一般只能到100-400Khz, SPI高达上百Mhz）

缺点:

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没有指定的流控制，没有应答机制确认是否接收到数据，所以跟IIC总线协议比较在数据可靠性上有一定的缺陷

1.2 硬体框架#

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SCK：提供时钟
DO:作为数据输出
DI:作为数据输入
CS0/CS1:作为片选

同一时刻只能有一个SPI设备处于工作状态。因此cs选中谁，谁就和主控通信。

1.2 数据传输时序#

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这里是一款SPI flash在SCLK上升延采样数据（D7~D0）的示意图。设现在s3c2440传输一个0x56数据给SPI Flash，时序如下：

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CS0低选中SPI Flash，配置成模式0， 0x56的二进制就是0b0101 0110，因此在每个SCK时钟周期，DO输出对应的电平。会在每个时钟周期的上升沿采样DO上的电平。

1.3 SPI相关的名词缩写#

KPOL： (Clock Polarity)（时钟）极性

CKPHA： (Clock Phase)（时钟）相位

SCK=SCLK：SPI的时钟

Leading edge：前一个边沿

Trailing edge：后一个边沿

1.4 时钟极性相位模式#

CPOL:表示SPI CLK的初始电平（空闲状态时电平），0为低电平，1为高电平

CPHA:表示相位，即第一个还是第二个时钟沿采样数据，0为第一个时钟沿，1为第二个时钟沿

两者组合成4种模式：

SPI模式 CPOL CPHA 空闲状态时钟极性 采样/移位时钟相位
0 0 0 低电平 上升沿采样（锁存）下降沿移位
1 0 1 低电平 上升沿移位下降沿采样（锁存）
2 1 0 高电平 上升沿移位下降沿采样（锁存）
3 1 1 高电平 上升沿采样（锁存）下降沿移位

4个模式波形对比：

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常用的是模式0和模式3，因为它们都是在上升沿采样数据.当配置成模式3时，对于主设备，数据采样在时钟上升沿，数据传送在时钟下降沿****。

主设备SPI时钟和极性的配置应该由外设来决定；二者的配置应该保持一致，即主设备的SDO同从设备的SDO配置一致，主设备的SDI同从设备的SDI配置一致。即因为主从设备是在SCLK的控制下，同时发送和接收数据，并通过2个双向移位寄存器来交换数据 。

举个例子，以 CPOL=0，CPHA=0，模式0为例：空闲CLK为低电平，相位为0，也就是上升延采集数据。由于SPI的全双工可以同时读写，发送MOSI数据为0xD2,接收MISO数据为0x66。

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2 SPI控制器结构#

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2.1 SSPSR#

SSPSR：移位寄存器(Shift Register). 根据 SPI 时钟同步信号, 将SSPBUF中的数据一位一位移出去或者收进来。

2.2 SSPBUF#

Master 与 Slave 之间交换的数据其实都是移位寄存器从 SSPBUF 里面拷贝的。通过往 SSPBUF 对应的寄存器 (Tx-Data / Rx-Data register) 里读写数据, 间接地操控 SPI 设备内部的 SSPBUF。

2.3 Controller#

用来发送控制信号的，像CS，SCK等控制信号。

3 SPI裸机示例#

3.1 SPI-OLED显示面板介绍#

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QG-2864TMBEG01这款OLED为例，可见它支持Parallel/i2c/SPI这3种方式对它进行控制，这里仅对它进行SPI控制。它的product Specification见附件。

3.1.1 并行接口时序#

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3.1.2 SPI串行接口时序#

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Tr/Tf: 表示spi clk上升/下降延不能超过40ns
Tclkl/Tclkh: 表示spi clk低/高电平持续至少20ns
Tcycle: 表示spi clk一个时钟周期至少100ns
Tdsw/Tdhw: 表示spi data的建立/持续时间至少15ms
Tcss:片选建立时间至少20ns
Tcsh:片选持续时间至少10ns
Tas/Tah:地址建立/持续时间至少15ns

3.1.3 power on sequence-上电序列#

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3.1.4 power down sequence-掉电序列#

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3.1.5 休眠唤醒#

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3.2 SPI-OLED面板显示原理#

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QG-2864TMBEG01这款为例，OLED长有128个像素，宽有64个像素，共128*64=8,192 像素。每个像素用1bit来表示，为1则亮，为0则灭。所以每一个字节数据Data表示8个像素，Data0~Data1023,如上图。 那要怎么在显存里面存放Data数据。

3.2.1 发送地址#

3.2.1.1 页(page)地址模式#

QG-2864TMBEG01 OLED主控有三种地址模式，我们常用的是页地址模式，发送0x20命令，再发送0x02命令，进入页地址模式，如下图：

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它把显存的64行分为8页，每页对应8行；选中某页后，再选择某列。因此共用页地址，也就是8行都共用同一个页地址，列地址独立，所以page0page7，col0col127。然后就可以往里面写数据了，每写一个数据，列地址就会加1，一直写到最右端的位置，页地址加1，会自动跳到最左端。通过命令来实现发送页地址和列地址，其中列地址分为两次发送，先发送低字节，再发送高字节。如下图，假设每个字符数据大小为8x16像素，假如第一个字符位置为(page,col)，相邻的右边就是(page,col+8)，写一个字符需要先发8字节，然后跳到下一页坐标就是(page+2,col)，发送8字节数据。一个字符需要2个page*8个col，由于一个像素占1个bit, 所以一个Data占1byte, 一个字符占16 byte。

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3.2.1.1.1 设置page addr#

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一共就8页，因此X2X0，有3bit足够了。比如选中page0，则x2x0 = 000。

3.2.1.1.2 设置col addr#

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分两次发送， 先发送列地址低4位，再发送列地址高4位；

3.2.2 发送数据#

如何发送一个字符‘A’，显示到OLED。

  1. 取得字模

这里从网上找了一份8x16的字库。

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#ifndef __OLEDFONT_H
#define __OLEDFONT_H      
const unsigned char oled_asc2_8x16[95][16]= {
    {0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00},// 0
    {0x00,0x00,0x00,0xF8,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x33,0x30,0x00,0x00,0x00},//!1
    {0x00,0x10,0x0C,0x06,0x10,0x0C,0x06,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00},//"2
    {0x40,0xC0,0x78,0x40,0xC0,0x78,0x40,0x00,0x04,0x3F,0x04,0x04,0x3F,0x04,0x04,0x00},//#3
    {0x00,0x70,0x88,0xFC,0x08,0x30,0x00,0x00,0x00,0x18,0x20,0xFF,0x21,0x1E,0x00,0x00},//$4
    {0xF0,0x08,0xF0,0x00,0xE0,0x18,0x00,0x00,0x00,0x21,0x1C,0x03,0x1E,0x21,0x1E,0x00},//%5
    {0x00,0xF0,0x08,0x88,0x70,0x00,0x00,0x00,0x1E,0x21,0x23,0x24,0x19,0x27,0x21,0x10},//&6
    {0x10,0x16,0x0E,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00},//'7
    {0x00,0x00,0x00,0xE0,0x18,0x04,0x02,0x00,0x00,0x00,0x00,0x07,0x18,0x20,0x40,0x00},//(8
    {0x00,0x02,0x04,0x18,0xE0,0x00,0x00,0x00,0x00,0x40,0x20,0x18,0x07,0x00,0x00,0x00},//)9
    {0x40,0x40,0x80,0xF0,0x80,0x40,0x40,0x00,0x02,0x02,0x01,0x0F,0x01,0x02,0x02,0x00},//*10
    {0x00,0x00,0x00,0xF0,0x00,0x00,0x00,0x00,0x01,0x01,0x01,0x1F,0x01,0x01,0x01,0x00},//+11
    {0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x80,0xB0,0x70,0x00,0x00,0x00,0x00,0x00},//,12
    {0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x01,0x01,0x01,0x01,0x01,0x01,0x01},//-13
    {0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x30,0x30,0x00,0x00,0x00,0x00,0x00},//.14
    {0x00,0x00,0x00,0x00,0x80,0x60,0x18,0x04,0x00,0x60,0x18,0x06,0x01,0x00,0x00,0x00},///15
    {0x00,0xE0,0x10,0x08,0x08,0x10,0xE0,0x00,0x00,0x0F,0x10,0x20,0x20,0x10,0x0F,0x00},//016
    {0x00,0x10,0x10,0xF8,0x00,0x00,0x00,0x00,0x00,0x20,0x20,0x3F,0x20,0x20,0x00,0x00},//117
    {0x00,0x70,0x08,0x08,0x08,0x88,0x70,0x00,0x00,0x30,0x28,0x24,0x22,0x21,0x30,0x00},//218
    {0x00,0x30,0x08,0x88,0x88,0x48,0x30,0x00,0x00,0x18,0x20,0x20,0x20,0x11,0x0E,0x00},//319
    {0x00,0x00,0xC0,0x20,0x10,0xF8,0x00,0x00,0x00,0x07,0x04,0x24,0x24,0x3F,0x24,0x00},//420
    {0x00,0xF8,0x08,0x88,0x88,0x08,0x08,0x00,0x00,0x19,0x21,0x20,0x20,0x11,0x0E,0x00},//521
    {0x00,0xE0,0x10,0x88,0x88,0x18,0x00,0x00,0x00,0x0F,0x11,0x20,0x20,0x11,0x0E,0x00},//622
    {0x00,0x38,0x08,0x08,0xC8,0x38,0x08,0x00,0x00,0x00,0x00,0x3F,0x00,0x00,0x00,0x00},//723
    {0x00,0x70,0x88,0x08,0x08,0x88,0x70,0x00,0x00,0x1C,0x22,0x21,0x21,0x22,0x1C,0x00},//824
    {0x00,0xE0,0x10,0x08,0x08,0x10,0xE0,0x00,0x00,0x00,0x31,0x22,0x22,0x11,0x0F,0x00},//925
    {0x00,0x00,0x00,0xC0,0xC0,0x00,0x00,0x00,0x00,0x00,0x00,0x30,0x30,0x00,0x00,0x00},//:26
    {0x00,0x00,0x00,0x80,0x00,0x00,0x00,0x00,0x00,0x00,0x80,0x60,0x00,0x00,0x00,0x00},//;27
    {0x00,0x00,0x80,0x40,0x20,0x10,0x08,0x00,0x00,0x01,0x02,0x04,0x08,0x10,0x20,0x00},//<28
    {0x40,0x40,0x40,0x40,0x40,0x40,0x40,0x00,0x04,0x04,0x04,0x04,0x04,0x04,0x04,0x00},//=29
    {0x00,0x08,0x10,0x20,0x40,0x80,0x00,0x00,0x00,0x20,0x10,0x08,0x04,0x02,0x01,0x00},//>30
    {0x00,0x70,0x48,0x08,0x08,0x08,0xF0,0x00,0x00,0x00,0x00,0x30,0x36,0x01,0x00,0x00},//?31
    {0xC0,0x30,0xC8,0x28,0xE8,0x10,0xE0,0x00,0x07,0x18,0x27,0x24,0x23,0x14,0x0B,0x00},//@32
    {0x00,0x00,0xC0,0x38,0xE0,0x00,0x00,0x00,0x20,0x3C,0x23,0x02,0x02,0x27,0x38,0x20},//A33
    {0x08,0xF8,0x88,0x88,0x88,0x70,0x00,0x00,0x20,0x3F,0x20,0x20,0x20,0x11,0x0E,0x00},//B34
    {0xC0,0x30,0x08,0x08,0x08,0x08,0x38,0x00,0x07,0x18,0x20,0x20,0x20,0x10,0x08,0x00},//C35
    {0x08,0xF8,0x08,0x08,0x08,0x10,0xE0,0x00,0x20,0x3F,0x20,0x20,0x20,0x10,0x0F,0x00},//D36
    {0x08,0xF8,0x88,0x88,0xE8,0x08,0x10,0x00,0x20,0x3F,0x20,0x20,0x23,0x20,0x18,0x00},//E37
    {0x08,0xF8,0x88,0x88,0xE8,0x08,0x10,0x00,0x20,0x3F,0x20,0x00,0x03,0x00,0x00,0x00},//F38
    {0xC0,0x30,0x08,0x08,0x08,0x38,0x00,0x00,0x07,0x18,0x20,0x20,0x22,0x1E,0x02,0x00},//G39
    {0x08,0xF8,0x08,0x00,0x00,0x08,0xF8,0x08,0x20,0x3F,0x21,0x01,0x01,0x21,0x3F,0x20},//H40
    {0x00,0x08,0x08,0xF8,0x08,0x08,0x00,0x00,0x00,0x20,0x20,0x3F,0x20,0x20,0x00,0x00},//I41
    {0x00,0x00,0x08,0x08,0xF8,0x08,0x08,0x00,0xC0,0x80,0x80,0x80,0x7F,0x00,0x00,0x00},//J42
    {0x08,0xF8,0x88,0xC0,0x28,0x18,0x08,0x00,0x20,0x3F,0x20,0x01,0x26,0x38,0x20,0x00},//K43
    {0x08,0xF8,0x08,0x00,0x00,0x00,0x00,0x00,0x20,0x3F,0x20,0x20,0x20,0x20,0x30,0x00},//L44
    {0x08,0xF8,0xF8,0x00,0xF8,0xF8,0x08,0x00,0x20,0x3F,0x00,0x3F,0x00,0x3F,0x20,0x00},//M45
    {0x08,0xF8,0x30,0xC0,0x00,0x08,0xF8,0x08,0x20,0x3F,0x20,0x00,0x07,0x18,0x3F,0x00},//N46
    {0xE0,0x10,0x08,0x08,0x08,0x10,0xE0,0x00,0x0F,0x10,0x20,0x20,0x20,0x10,0x0F,0x00},//O47
    {0x08,0xF8,0x08,0x08,0x08,0x08,0xF0,0x00,0x20,0x3F,0x21,0x01,0x01,0x01,0x00,0x00},//P48
    {0xE0,0x10,0x08,0x08,0x08,0x10,0xE0,0x00,0x0F,0x18,0x24,0x24,0x38,0x50,0x4F,0x00},//Q49
    {0x08,0xF8,0x88,0x88,0x88,0x88,0x70,0x00,0x20,0x3F,0x20,0x00,0x03,0x0C,0x30,0x20},//R50
    {0x00,0x70,0x88,0x08,0x08,0x08,0x38,0x00,0x00,0x38,0x20,0x21,0x21,0x22,0x1C,0x00},//S51
    {0x18,0x08,0x08,0xF8,0x08,0x08,0x18,0x00,0x00,0x00,0x20,0x3F,0x20,0x00,0x00,0x00},//T52
    {0x08,0xF8,0x08,0x00,0x00,0x08,0xF8,0x08,0x00,0x1F,0x20,0x20,0x20,0x20,0x1F,0x00},//U53
    {0x08,0x78,0x88,0x00,0x00,0xC8,0x38,0x08,0x00,0x00,0x07,0x38,0x0E,0x01,0x00,0x00},//V54
    {0xF8,0x08,0x00,0xF8,0x00,0x08,0xF8,0x00,0x03,0x3C,0x07,0x00,0x07,0x3C,0x03,0x00},//W55
    {0x08,0x18,0x68,0x80,0x80,0x68,0x18,0x08,0x20,0x30,0x2C,0x03,0x03,0x2C,0x30,0x20},//X56
    {0x08,0x38,0xC8,0x00,0xC8,0x38,0x08,0x00,0x00,0x00,0x20,0x3F,0x20,0x00,0x00,0x00},//Y57
    {0x10,0x08,0x08,0x08,0xC8,0x38,0x08,0x00,0x20,0x38,0x26,0x21,0x20,0x20,0x18,0x00},//Z58
    {0x00,0x00,0x00,0xFE,0x02,0x02,0x02,0x00,0x00,0x00,0x00,0x7F,0x40,0x40,0x40,0x00},//[59
    {0x00,0x0C,0x30,0xC0,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x01,0x06,0x38,0xC0,0x00},//\60
    {0x00,0x02,0x02,0x02,0xFE,0x00,0x00,0x00,0x00,0x40,0x40,0x40,0x7F,0x00,0x00,0x00},//]61
    {0x00,0x00,0x04,0x02,0x02,0x02,0x04,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00},//^62
    {0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x80,0x80,0x80,0x80,0x80,0x80,0x80,0x80},//_63
    {0x00,0x02,0x02,0x04,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00},//`64
    {0x00,0x00,0x80,0x80,0x80,0x80,0x00,0x00,0x00,0x19,0x24,0x22,0x22,0x22,0x3F,0x20},//a65
    {0x08,0xF8,0x00,0x80,0x80,0x00,0x00,0x00,0x00,0x3F,0x11,0x20,0x20,0x11,0x0E,0x00},//b66
    {0x00,0x00,0x00,0x80,0x80,0x80,0x00,0x00,0x00,0x0E,0x11,0x20,0x20,0x20,0x11,0x00},//c67
    {0x00,0x00,0x00,0x80,0x80,0x88,0xF8,0x00,0x00,0x0E,0x11,0x20,0x20,0x10,0x3F,0x20},//d68
    {0x00,0x00,0x80,0x80,0x80,0x80,0x00,0x00,0x00,0x1F,0x22,0x22,0x22,0x22,0x13,0x00},//e69
    {0x00,0x80,0x80,0xF0,0x88,0x88,0x88,0x18,0x00,0x20,0x20,0x3F,0x20,0x20,0x00,0x00},//f70
    {0x00,0x00,0x80,0x80,0x80,0x80,0x80,0x00,0x00,0x6B,0x94,0x94,0x94,0x93,0x60,0x00},//g71
    {0x08,0xF8,0x00,0x80,0x80,0x80,0x00,0x00,0x20,0x3F,0x21,0x00,0x00,0x20,0x3F,0x20},//h72
    {0x00,0x80,0x98,0x98,0x00,0x00,0x00,0x00,0x00,0x20,0x20,0x3F,0x20,0x20,0x00,0x00},//i73
    {0x00,0x00,0x00,0x80,0x98,0x98,0x00,0x00,0x00,0xC0,0x80,0x80,0x80,0x7F,0x00,0x00},//j74
    {0x08,0xF8,0x00,0x00,0x80,0x80,0x80,0x00,0x20,0x3F,0x24,0x02,0x2D,0x30,0x20,0x00},//k75
    {0x00,0x08,0x08,0xF8,0x00,0x00,0x00,0x00,0x00,0x20,0x20,0x3F,0x20,0x20,0x00,0x00},//l76
    {0x80,0x80,0x80,0x80,0x80,0x80,0x80,0x00,0x20,0x3F,0x20,0x00,0x3F,0x20,0x00,0x3F},//m77
    {0x80,0x80,0x00,0x80,0x80,0x80,0x00,0x00,0x20,0x3F,0x21,0x00,0x00,0x20,0x3F,0x20},//n78
    {0x00,0x00,0x80,0x80,0x80,0x80,0x00,0x00,0x00,0x1F,0x20,0x20,0x20,0x20,0x1F,0x00},//o79
    {0x80,0x80,0x00,0x80,0x80,0x00,0x00,0x00,0x80,0xFF,0xA1,0x20,0x20,0x11,0x0E,0x00},//p80
    {0x00,0x00,0x00,0x80,0x80,0x80,0x80,0x00,0x00,0x0E,0x11,0x20,0x20,0xA0,0xFF,0x80},//q81
    {0x80,0x80,0x80,0x00,0x80,0x80,0x80,0x00,0x20,0x20,0x3F,0x21,0x20,0x00,0x01,0x00},//r82
    {0x00,0x00,0x80,0x80,0x80,0x80,0x80,0x00,0x00,0x33,0x24,0x24,0x24,0x24,0x19,0x00},//s83
    {0x00,0x80,0x80,0xE0,0x80,0x80,0x00,0x00,0x00,0x00,0x00,0x1F,0x20,0x20,0x00,0x00},//t84
    {0x80,0x80,0x00,0x00,0x00,0x80,0x80,0x00,0x00,0x1F,0x20,0x20,0x20,0x10,0x3F,0x20},//u85
    {0x80,0x80,0x80,0x00,0x00,0x80,0x80,0x80,0x00,0x01,0x0E,0x30,0x08,0x06,0x01,0x00},//v86
    {0x80,0x80,0x00,0x80,0x00,0x80,0x80,0x80,0x0F,0x30,0x0C,0x03,0x0C,0x30,0x0F,0x00},//w87
    {0x00,0x80,0x80,0x00,0x80,0x80,0x80,0x00,0x00,0x20,0x31,0x2E,0x0E,0x31,0x20,0x00},//x88
    {0x80,0x80,0x80,0x00,0x00,0x80,0x80,0x80,0x80,0x81,0x8E,0x70,0x18,0x06,0x01,0x00},//y89
    {0x00,0x80,0x80,0x80,0x80,0x80,0x80,0x00,0x00,0x21,0x30,0x2C,0x22,0x21,0x30,0x00},//z90
    {0x00,0x00,0x00,0x00,0x80,0x7C,0x02,0x02,0x00,0x00,0x00,0x00,0x00,0x3F,0x40,0x40},//{91
    {0x00,0x00,0x00,0x00,0xFF,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0xFF,0x00,0x00,0x00},//|92
    {0x00,0x02,0x02,0x7C,0x80,0x00,0x00,0x00,0x00,0x40,0x40,0x3F,0x00,0x00,0x00,0x00},//}93
    {0x00,0x06,0x01,0x01,0x02,0x02,0x04,0x04,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00},//~94
};     
#endif

  1. 发送页/列地址

  2. 发送数据

3.3 SPI-OLED驱动-GPIO模拟SPI方式#

3.3.1 软件层次#

操作OLED，通过三条线(SCK、DO、CS)与OLED相连，这里没有DI是因为s3c2440只会向OLED传数据而不用接收数据。

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gpio_spi.c来实现gpio模拟spi，负责spi通讯。对于OLED，有专门的指令和数据格式，要传输的数据内容。
oled.c这一层来实现，负责组织数据。

3.3.2 gpio_spi.c#

img

3.3.2.1 spi引脚初始化#

上图J3为板子pin2pin到OLED的底座。

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GPF1作为OLED片选引脚，设置为输出；
GPG4作为OLED的数据(Data)/命令(Command)选择引脚，设置为输出；
GPG5作为SPI的MISO，设置为输入（实际用不到）；
GPG6作为SPI的MOSI，设置为输出；
GPG7作为SPI的时钟CLK，设置为输出；

img

img

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void SPIInit(void) {
    /* 初始化引脚 */
    SPI_GPIO_Init();
}
static void SPI_GPIO_Init(void) {
    /* GPF1 as OLED_CSn output */
    GPFCON &= ~(3<<(1*2));
    GPFCON |= (1<<(1*2));
    GPFDAT |= (1<<1);//取消OLED_CSn片选，pull up
   /* GPG2 FLASH_CSn output
    * GPG4 OLED_DC   output
    * GPG5 SPIMISO   input
    * GPG6 SPIMOSI   output
    * GPG7 SPICLK    output
    */
    GPGCON &= ~((3<<(2*2)) | (3<<(4*2)) | (3<<(5*2)) | (3<<(6*2)) | (3<<(7*2)));
    GPGCON |= ((1<<(2*2)) | (1<<(4*2)) | (1<<(6*2)) | (1<<(7*2)));
    GPGDAT |= (1<<2);//取消FLASH_CSn 片选，pull up
}

3.3.2.2 写命令#

D/C即数据(Data)/命令(Command)选择引脚，它为高电平时，OLED即认为收到的是数据；它为低电平时，OLED即认为收到的是命令。先设置为命令模式，再片选OLED，再传输命令，再恢复成原来的模式和取消片选。

img

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static void SPI_Set_DO(char val) {
    if (val)
        GPGDAT |= (1<<6);
    else
        GPGDAT &= ~(1<<6);
}
static void SPI_Set_CLK(char val) {
    if (val)
        GPGDAT |= (1<<7);
    else
        GPGDAT &= ~(1<<7);
}
void SPISendByte(unsigned char val) {
    int i;
    for (i = 0; i < 8; i++){
        SPI_Set_CLK(0);
        SPI_Set_DO(val & 0x80);//MSB
        SPI_Set_CLK(1);
        val <<= 1;
    }
}
static void OLED_Set_DC(char val) {
    if (val)
        GPGDAT |= (1<<4);
    else
        GPGDAT &= ~(1<<4);
}
static void OLED_Set_CS(char val) {
    if (val)
        GPFDAT |= (1<<1);
    else
        GPFDAT &= ~(1<<1);
}
static void OLEDWriteCmd(unsigned char cmd) {
    OLED_Set_DC(0); /* command */
    OLED_Set_CS(0); /* select OLED */
    SPISendByte(cmd);
    OLED_Set_CS(1); /* de-select OLED */
    OLED_Set_DC(1); /*  gpio output default is pull up*/
}

  1. 拉低DC引脚表示要发送是命令；

  2. 片选

  3. 发送1byte数据

3.3.2.2.1 SPISendByte#

img
SPISendByte是把一个byte数据从高位往低位依次发送到DO。spi配置模式0， 主控先设置CLK为低，由于是MSB, 先传送高位，然后CLK为高，在CLK这个上升沿,DO的数据被锁存，OLED就读取了一位数据。接着左移一位，传输下一位。通过SPI_Set_CLK()和SPI_Set_DO()配置SCK和DO的时序，用gpio模拟出了spi。至此，SPI初始化和OLED初始化就基本完成了，接下来就是OLED显示部分。

这里gpio模拟spi传送时主控没有加延时控制SCK的频率，那是由于s3c2440本身cpu运行就很慢，这里不延时也是能满足该款外设的spi传输时序，如果cpu很快，那么需要控制spi时序。

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//每隔一个SPI时钟，发送1位数据，MSB-高位先出
//这里的SPI时钟并没有指定周期，这就取决于指令执行的速率，指令执行越快，gpio模拟的SPI时钟越快,如下：     
void SPISendByte(unsigned char val) {
          int i;
          for (i = 0; i < 8; i++) {
              SPI_Set_CLK(0);
              SPI_Set_DO(val & 0x80);//MSB
              SPI_Set_CLK(1);
              val <<= 1;
          }
 }
  1. 取消片选
  2. DC拉高

3.3.2.3 写数据#

与写命令同理：

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static void OLEDWriteDat(unsigned char data){
    OLED_Set_DC(1); /* data*/
    OLED_Set_CS(0); /* select OLED */
    SPISendByte(data);
    OLED_Set_CS(1); /* de-select OLED */
}

3.2.3 oled.c#

3.2.3.1 初始化OLED#

找到QG-2864TMBEG01 的power on sequence-上电时序。

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void OLEDInit(void){
    /* 向OLED发命令以初始化 */
    OLEDWriteCmd(0xAE); /*display off*/
    OLEDWriteCmd(0x00); /*set lower column address*/
    OLEDWriteCmd(0x10); /*set higher column address*/
    OLEDWriteCmd(0x40); /*set display start line*/
    OLEDWriteCmd(0xB0); /*set page address*/
    OLEDWriteCmd(0x81); /*contract control*/
    OLEDWriteCmd(0x66); /*128*/
    OLEDWriteCmd(0xA1); /*set segment remap*/
    OLEDWriteCmd(0xA6); /*normal / reverse*/
    OLEDWriteCmd(0xA8); /*multiplex ratio*/
    OLEDWriteCmd(0x3F); /*duty = 1/64*/
    OLEDWriteCmd(0xC8); /*Com scan direction*/
    OLEDWriteCmd(0xD3); /*set display offset*/
    OLEDWriteCmd(0x00);
    OLEDWriteCmd(0xD5); /*set osc division*/
    OLEDWriteCmd(0x80);
    OLEDWriteCmd(0xD9); /*set pre-charge period*/
    OLEDWriteCmd(0x1f);
    OLEDWriteCmd(0xDA); /*set COM pins*/
    OLEDWriteCmd(0x12);
    OLEDWriteCmd(0xdb); /*set vcomh*/
    OLEDWriteCmd(0x30);
    OLEDWriteCmd(0x8d); /*set charge pump enable*/
    OLEDWriteCmd(0x14);
}

3.2.3.2 驱动显示OLED#

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static void OLEDSetPos(int page, int col) {
    OLEDWriteCmd(0xB0 + page); /* page address */
    OLEDWriteCmd(col & 0xf);   /* Lower Column Start Address */
    OLEDWriteCmd(0x10 + (col >> 4));   /* Lower Higher Start Address */
}
/* page: 0-7
 * col : 0-127
 * 字符: 8x16象素
 */
void OLEDPutChar(int page, int col, char c) {
    int i = 0;
    /* 得到字模 */
    const unsigned char *dots = oled_asc2_8x16[c - ' '];
    /* 发给OLED */
    OLEDSetPos(page, col);
    /* 发出8字节数据 */
    for (i = 0; i < 8; i++)
        OLEDWriteDat(dots[i]);
    OLEDSetPos(page+1, col);
    /* 发出8字节数据 */
    for (i = 0; i < 8; i++)
        OLEDWriteDat(dots[i+8]);
}
/* page: 0-7
 * col : 0-127
 * 字符: 8x16象素
 */
void OLEDPrint(int page, int col, char *str) {
    int i = 0;
    while (str[i]) {
        OLEDPutChar(page, col, str[i]);
        col += 8;
        if (col > 127) {
            col = 0;
            page += 2;
        }
        i++;
    }
}
static void OLEDSetPos(int page, int col) {
    OLEDWriteCmd(0xB0 + page); /* page address */
    OLEDWriteCmd(col & 0xf);   /* Lower Column Start Address */
    OLEDWriteCmd(0x10 + (col >> 4));   /* Lower Higher Start Address */
}
static void OLEDClear(void) {
    int page, i;
    for (page = 0; page < 8; page ++) {
        OLEDSetPos(page, 0);
        for (i = 0; i < 128; i++)
            OLEDWriteDat(0);
    }
}

3.3.4 完整代码#

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/************************** gpio_spi.c ****************/
#include "s3c24xx.h"
/* 用GPIO模拟SPI */
static void SPI_GPIO_Init(void)
{
    /* GPF1 OLED_CSn output */
    GPFCON &= ~(3<<(1*2));
    GPFCON |= (1<<(1*2));
    GPFDAT |= (1<<1);
 
    /* GPG2 FLASH_CSn output
    * GPG4 OLED_DC   output
    * GPG5 SPIMISO   input
    * GPG6 SPIMOSI   output
    * GPG7 SPICLK    output
    */
    GPGCON &= ~((3<<(2*2)) | (3<<(4*2)) | (3<<(5*2)) | (3<<(6*2)) | (3<<(7*2)));
    GPGCON |= ((1<<(2*2)) | (1<<(4*2)) | (1<<(6*2)) | (1<<(7*2)));
    GPGDAT |= (1<<2);
}
 
static void SPI_Set_CLK(char val)
{
    if (val)
        GPGDAT |= (1<<7);
    else
        GPGDAT &= ~(1<<7);
}
 
static void SPI_Set_DO(char val)
{
    if (val)
        GPGDAT |= (1<<6);
    else
        GPGDAT &= ~(1<<6);
}
 
void SPISendByte(unsigned char val)
{
    int i;
    for (i = 0; i < 8; i++)
    {
        SPI_Set_CLK(0);
        SPI_Set_DO(val & 0x80);
        SPI_Set_CLK(1);
        val <<= 1;
    }
     
}
 
void SPIInit(void)
{
    /* 初始化引脚 */
    SPI_GPIO_Init();
}
 
/******************* oled.c****************/
#include "oledfont.h"
#include "gpio_spi.h"
#include "s3c24xx.h"
static void OLED_Set_DC(char val)
{
    if (val)
        GPGDAT |= (1<<4);
    else
        GPGDAT &= ~(1<<4);
}
static void OLED_Set_CS(char val)
{
    if (val)
        GPFDAT |= (1<<1);
    else
        GPFDAT &= ~(1<<1);
}
static void OLEDWriteCmd(unsigned char cmd)
{
    OLED_Set_DC(0); /* command */
    OLED_Set_CS(0); /* select OLED */
 
    SPISendByte(cmd);
 
    OLED_Set_CS(1); /* de-select OLED */
    OLED_Set_DC(1); /*  */
}
static void OLEDWriteDat(unsigned char dat)
{
    OLED_Set_DC(1); /* data */
    OLED_Set_CS(0); /* select OLED */
 
    SPISendByte(dat);
 
    OLED_Set_CS(1); /* de-select OLED */
    OLED_Set_DC(1); /*  */
}
static void OLEDSetPageAddrMode(void)
{
    OLEDWriteCmd(0x20);
    OLEDWriteCmd(0x02);
}
static void OLEDSetPos(int page, int col)
{
    OLEDWriteCmd(0xB0 + page); /* page address */
 
    OLEDWriteCmd(col & 0xf);   /* Lower Column Start Address */
    OLEDWriteCmd(0x10 + (col >> 4));   /* Lower Higher Start Address */
}
static void OLEDClear(void)
{
    int page, i;
    for (page = 0; page < 8; page ++)
    {
        OLEDSetPos(page, 0);
        for (i = 0; i < 128; i++)
            OLEDWriteDat(0);
    }
}
void OLEDInit(void)
{
    /* 向OLED发命令以初始化 */
    OLEDWriteCmd(0xAE); /*display off*/
    OLEDWriteCmd(0x00); /*set lower column address*/
    OLEDWriteCmd(0x10); /*set higher column address*/
    OLEDWriteCmd(0x40); /*set display start line*/
    OLEDWriteCmd(0xB0); /*set page address*/
    OLEDWriteCmd(0x81); /*contract control*/
    OLEDWriteCmd(0x66); /*128*/
    OLEDWriteCmd(0xA1); /*set segment remap*/
    OLEDWriteCmd(0xA6); /*normal / reverse*/
    OLEDWriteCmd(0xA8); /*multiplex ratio*/
    OLEDWriteCmd(0x3F); /*duty = 1/64*/
    OLEDWriteCmd(0xC8); /*Com scan direction*/
    OLEDWriteCmd(0xD3); /*set display offset*/
    OLEDWriteCmd(0x00);
    OLEDWriteCmd(0xD5); /*set osc division*/
    OLEDWriteCmd(0x80);
    OLEDWriteCmd(0xD9); /*set pre-charge period*/
    OLEDWriteCmd(0x1f);
    OLEDWriteCmd(0xDA); /*set COM pins*/
    OLEDWriteCmd(0x12);
    OLEDWriteCmd(0xdb); /*set vcomh*/
    OLEDWriteCmd(0x30);
    OLEDWriteCmd(0x8d); /*set charge pump enable*/
    OLEDWriteCmd(0x14);
 
    OLEDSetPageAddrMode();
 
    OLEDClear();
     
    OLEDWriteCmd(0xAF); /*display ON*/   
}
 
/* page: 0-7
 * col : 0-127
 * 字符: 8x16象素
 */
void OLEDPutChar(int page, int col, char c)
{
    int i = 0;
    /* 得到字模 */
    const unsigned char *dots = oled_asc2_8x16[c - ' '];
 
    /* 发给OLED */
    OLEDSetPos(page, col);
    /* 发出8字节数据 */
    for (i = 0; i < 8; i++)
        OLEDWriteDat(dots[i]);
 
    OLEDSetPos(page+1, col);
    /* 发出8字节数据 */
    for (i = 0; i < 8; i++)
        OLEDWriteDat(dots[i+8]);
 
}
 
/* page: 0-7
 * col : 0-127
 * 字符: 8x16象素
 */
void OLEDPrint(int page, int col, char *str)
{
    int i = 0;
    while (str[i])
    {
        OLEDPutChar(page, col, str[i]);
        col += 8;
        if (col > 127)
        {
            col = 0;
            page += 2;
        }
        i++;
    }
}