PIC32MX470的温湿度计：调SPI和OLED显示实验

温湿度可以正常读取了，接下来就是调SPI和OLED显示，尝试将数据通过OLED屏显示出来。

查看OLED屏的资料，支持多种连接方式，默认的是4线SPI，但是没有MISO，也就是说OLED屏没有输出信号，不可读。那就在Information sheet上找SPI的管脚，老原因接着用用X32接口上的SPI2。为了接线方便些，用邻近的管脚作RST和DC信号

由于X32上只有一个3.3V，温湿度传感器最高耐压5.5V，就把它接到5V上吧，按如下方式连接OLED屏和温湿度传感器

接下来依然是通过MHC来使能SPI驱动

1. 打开MHC的Options选项卡，找到SPI对应的driver选项打开并做相应的配置，我的配置如下

2. 打开MHC的Pin Settings，将RG6、RG7、RG8、RG9设置为SPI管脚，RB8设置为DC，RD7设置为RST

3. 然后生成代码，主要包含以下几个源文件

4. 分析SPI驱动代码后可知在SYS_Initialize中已经根据用户的配置调用了SPI相关的初始化函数，所以使用时只需要在代码里直接调用drv_spi_mapping.c中的其他API就可以了。但是SPI的速率较高，我设置的是5M，如果使用中断模式，处理不好中断频繁产生的话，不知道CPU是不是吃得消；以前在SAM4N上用过轮询方式的SPI，索性将代码拿来直接用，等到调通了之后再改成中断甚至DMA看能不能处理好。先不用MHC产生的代码了，相当于只利用了它的初始化和访问硬件的PLIB库。主要的spi和ssd1306的代码如下

bsp_spi.c

void spi_select_device(PORTS_CHANNEL ch, PORTS_BIT_POS pos)

{

SYS_PORTS_PinClear(PORTS_ID_0, ch, pos);

}

void spi_deselect_device(PORTS_CHANNEL ch, PORTS_BIT_POS pos)

{

SYS_PORTS_PinSet(PORTS_ID_0, ch, pos);

}

static inline void spi_write_single(uint8_t data)

{

PLIB_SPI_BufferWrite(SPI_ID_2, data);

}

bsp_ssd1306.c

#define SSD1306_SPI_INTERFACE

#define SSD1306_SPI                     SPI

#define SSD1306_DC_PIN_CH               PORT_CHANNEL_B

#define SSD1306_DC_PIN_POS              PORTS_BIT_POS_8

#define SSD1306_CS_PIN_CH               PORT_CHANNEL_G

#define SSD1306_CS_PIN_POS              PORTS_BIT_POS_9

#define SSD1306_RES_PIN_CH              PORT_CHANNEL_D

#define SSD1306_RES_PIN_POS             PORTS_BIT_POS_7

#define UG_2832HSWEG04_BAUDRATE         5000000

#define SSD1306_LATENCY 10

#define ssd1306_reset_clear()    SYS_PORTS_PinClear(PORTS_ID_0, SSD1306_RES_PIN_CH, SSD1306_RES_PIN_POS)

#define ssd1306_reset_set()      SYS_PORTS_PinSet(PORTS_ID_0, SSD1306_RES_PIN_CH, SSD1306_RES_PIN_POS)

// Data/CMD select, PC21Could not add reference to assembly IronPython.wpf

#define ssd1306_sel_data()       SYS_PORTS_PinSet(PORTS_ID_0, SSD1306_DC_PIN_CH, SSD1306_DC_PIN_POS)

#define ssd1306_sel_cmd()        SYS_PORTS_PinClear(PORTS_ID_0, SSD1306_DC_PIN_CH, SSD1306_DC_PIN_POS)

static inline void delay_us(unsigned int n)

{

volatile uint32_t i;

volatile uint32_t j;

i = (n > 0) ? n : 1;

for (; i > 0; i--) {

for (j = 0; j < 100; j++) {

;

}

}

}

static inline void ssd1306_write_command(uint8_t command)

{

spi_select_device(SSD1306_CS_PIN_CH, SSD1306_CS_PIN_POS);

ssd1306_sel_cmd();

spi_write_single(command);

delay_us(SSD1306_LATENCY); // At least 3us

spi_deselect_device(SSD1306_CS_PIN_CH, SSD1306_CS_PIN_POS);

}

static inline void ssd1306_write_data(uint8_t data)

{

spi_select_device(SSD1306_CS_PIN_CH, SSD1306_CS_PIN_POS);

ssd1306_sel_data();

spi_write_single(data);

delay_us(SSD1306_LATENCY); // At least 3us

spi_deselect_device(SSD1306_CS_PIN_CH, SSD1306_CS_PIN_POS);

}

static inline void ssd1306_hard_reset(void)

{

ssd1306_reset_clear();

delay_us(SSD1306_LATENCY); // At least 3us

ssd1306_reset_set();

delay_us(SSD1306_LATENCY); // At least 3us

}

static inline void ssd1306_set_page_address(uint8_t address)

{

// Make sure that the address is 4 bits (only 8 pages)

address &= 0x0F;

ssd1306_write_command(SSD1306_CMD_SET_PAGE_START_ADDRESS(address));

}

static inline void ssd1306_set_column_address(uint8_t address)

{

// Make sure the address is 7 bits

address &= 0x7F;

ssd1306_write_command(SSD1306_CMD_SET_HIGH_COL(address >> 4));

ssd1306_write_command(SSD1306_CMD_SET_LOW_COL(address & 0x0F));

}

static inline void ssd1306_clear(void)

{

uint8_t page = 0;

uint8_t col = 0;

for (page = 0; page < 8; ++page)

{

ssd1306_set_page_address(page);

ssd1306_set_column_address(0);

for (col = 0; col < 128; ++col)

{

ssd1306_write_data(0x00);

}

}

}

void ssd1306_init(void)

{

// Do a hard reset of the OLED display controller

ssd1306_hard_reset();

// Initialize the interface

ssd1306_interface_init();

// 1/32 Duty (0x0F~0x3F)

ssd1306_write_command(SSD1306_CMD_SET_MULTIPLEX_RATIO);

ssd1306_write_command(0x3F);

// Shift Mapping RAM Counter (0x00~0x3F)

ssd1306_write_command(SSD1306_CMD_SET_DISPLAY_OFFSET);

ssd1306_write_command(0x00);

// Set Mapping RAM Display Start Line (0x00~0x3F)

ssd1306_write_command(SSD1306_CMD_SET_START_LINE(0x00));

// Set Column Address 0 Mapped to SEG0

ssd1306_write_command(SSD1306_CMD_SET_SEGMENT_RE_MAP_COL127_SEG0);

// Set COM/Row Scan Scan from COM63 to 0

ssd1306_write_command(SSD1306_CMD_SET_COM_OUTPUT_SCAN_DOWN);

// Set COM Pins hardware configuration

ssd1306_write_command(SSD1306_CMD_SET_COM_PINS);

ssd1306_write_command(0x12);

ssd1306_set_contrast(0x8F);

// Disable Entire display On

ssd1306_write_command(SSD1306_CMD_ENTIRE_DISPLAY_AND_GDDRAM_ON);

ssd1306_display_invert_disable();

// Set Display Clock Divide Ratio / Oscillator Frequency (Default => 0x80)

ssd1306_write_command(SSD1306_CMD_SET_DISPLAY_CLOCK_DIVIDE_RATIO);

ssd1306_write_command(0x80);

// Enable charge pump regulator

ssd1306_write_command(SSD1306_CMD_SET_CHARGE_PUMP_SETTING);

ssd1306_write_command(0x14);

// Set VCOMH Deselect Level

ssd1306_write_command(SSD1306_CMD_SET_VCOMH_DESELECT_LEVEL);

ssd1306_write_command(0x40); // Default => 0x20 (0.77*VCC)

// Set Pre-Charge as 15 Clocks & Discharge as 1 Clock

ssd1306_write_command(SSD1306_CMD_SET_PRE_CHARGE_PERIOD);

ssd1306_write_command(0xF1);

ssd1306_display_on();

}

void ssd1306_write_text(const char *string)

{

uint8_t *char_ptr;

uint8_t i;

while (*string != 0) {

if (*string < 0x7F) {

char_ptr = font_table[*string - 32];

for (i = 1; i <= char_ptr[0]; i++) {

ssd1306_write_data(char_ptr[i]);

}

ssd1306_write_data(0x00);

}

string++;

}

}

5. 最后在APP_Tasks中初始化ssd1306，把原先读温湿度操作之后的串口打印，改成显示数据，每秒读一次并通过OLED屏显示出来

调试还算顺利，OLED显示如下

虽然显示的终端由串口改成了OLED屏，但换个马甲依然无法掩饰它的简陋。下一步就是移植μGUI装一回大尾巴狼，哈哈哈