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12. External Flash (SPI)
External Flash (SPI)
External Flash (SPI)I. Learning ObjectivesII. SPI IntroductionIII. Hardware SetupIV. Environment SetupV. Main FunctionsVI. Experiment Phenomenon
I. Learning Objectives
- Learn and understand basic SPI communication knowledge.
- Learn to drive W25Q64 through SPI.
II. SPI Introduction
SPI protocol (Serial Peripheral Interface) is a commonly used synchronous serial communication protocol, specially designed for high-speed, short-distance communication between microcontrollers and external devices. It supports full-duplex communication, meaning data can be sent and received simultaneously between master and slave devices, commonly used for memory chips, sensors, display drivers, and wireless modules.
SPI Hardware Interface
SPI protocol typically uses four lines for data transmission:
- SCLK (Serial Clock): Clock signal generated by master device, used for synchronizing communication.
- MOSI/PICO (Master Output Slave Input): Master device sends data to slave device.
- MISO/POCI (Master Input Slave Output): Slave device sends data to master device.
- SS/CS (Slave Select): Master device activates target slave device through chip select signal.
SPI Advantages
- High communication speed, suitable for high-bandwidth applications.
- Supports full-duplex transmission, improving efficiency.
- Simple hardware implementation, direct interface.
- Supports multiple slave device connections.
SPI Disadvantages
- Lacks standardized error detection mechanism.
- Master device pin count increases with number of slave devices.
- Communication distance is limited, typically used for onboard communication.
SPI Transmission Modes
Clock Polarity (CPOL): Controls the idle and active states of the clock signal (0: idle state low level, 1: idle state high level)
Clock Phase (CPHA): Controls data sampling and transmission timing (0: sample on odd edge, 1: sample on even edge)
| Clock Polarity (CPOL) | Clock Phase (CPHA) | |
|---|---|---|
| 0 | 0 | SCL idle state low level; data sampled on rising edge, transmitted on falling edge |
| 0 | 1 | SCL idle state low level; data sampled on falling edge, transmitted on rising edge |
| 1 | 0 | SCL idle state high level; data sampled on falling edge, transmitted on rising edge |
| 1 | 1 | SCL idle state high level; data sampled on rising edge, transmitted on falling edge |
CPOL:0 CPHA:0
CPOL:0 CPHA:1
CPOL:1 CPHA:0
CPOL:1 CPHA:1
III. Hardware Setup
W25Q64 is a common serial flash memory device that uses SPI (Serial Peripheral Interface) protocol. It has high-speed read, write, and erase functions, widely used in embedded systems, storage devices, routers, and other high-performance electronic devices. W25Q32 has a capacity of 64 Mbit (i.e., 8 MB). The numbers in the model represent different capacity options, such as W25Q16, W25Q32, W25Q128, etc., to meet the needs of different application scenarios.
W25Q64 divides 8M bytes of capacity into 128 blocks, each block size is 64K bytes, each block is divided into 16 sectors, each sector is 4K bytes. The minimum erase unit of W25Q64 is one sector, which means 4K bytes must be erased each time. Partial instruction table content is as follows
This course requires no additional hardware equipment, directly using the onboard LCD screen and external storage flash on the MSPM0G3507 development board.
Connection relationship is as follows
IV. Environment Setup
First, we add configuration through sysconfig as follows
Unlike the previous section, this section uses hardware I2C to drive the OLED screen
V. Main Functions
Mainly introduces the user-written functional code, for detailed code, you can open the project files we provide and enter the Bsp folder to view the source code.
W25Qxx_Init
| Function Prototype | void W25Qxx_Init(void) |
|---|---|
| Function Description | Initialize W25Q64 Flash, main operation is to pull SPI_CS pin high and delay 300ms to ensure stable initialization |
| Input Parameters | None |
| Return Value | None |
spi_read_write_byte
| Function Prototype | uint8_t spi_read_write_byte(uint8_t dat) |
|---|---|
| Function Description | Complete SPI single byte transmit/receive: first send input dat byte, wait for SPI bus idle, then receive byte returned from slave device |
| Input Parameters | dat (uint8_t type, single byte data to be sent through SPI) |
| Return Value | uint8_t type, byte returned from slave device received by SPI bus |
W25QXX_Self_Test
| Function Prototype | void W25QXX_Self_Test(void) |
|---|---|
| Function Description | Flash self-test: loop read Flash ID and identify model (W25Q32/W25Q64/W25Q128), display model through OLED and print via serial port; simultaneously test Flash read/write function (write "Yahboom" and verify), print read/write results |
| Input Parameters | None |
| Return Value | None |
W25Qxx_readID
| Function Prototype | uint16_t W25Qxx_readID(void) |
|---|---|
| Function Description | Read W25Q64 device ID: send 0x90 instruction and 0x000000 address, receive 2-byte ID and concatenate to return |
| Input Parameters | None |
| Return Value | uint16_t type, Flash device ID (e.g., W25Q64 corresponding ID is 0xEF16) |
W25Qxx_write_enable
| Function Prototype | void W25Qxx_write_enable(void) |
|---|---|
| Function Description | Send "write enable" instruction (0x06) to Flash, allowing subsequent write/erase operations |
| Input Parameters | None |
| Return Value | None |
W25Qxx_wait_busy
| Function Prototype | void W25Qxx_wait_busy(void) |
|---|---|
| Function Description | Wait for Flash operation to complete: loop read status register, detect BUSY bit (lowest bit), until BUSY bit is 0 (indicating Flash is idle) |
| Input Parameters | None |
| Return Value | None |
W25Qxx_erase_sector
| Function Prototype | void W25Qxx_erase_sector(uint32_t addr) |
|---|---|
| Function Description | Erase specified sector: first convert input address to sector address (1 sector = 4096 bytes), send sector erase instruction (0x20) and address, wait for erase completion |
| Input Parameters | addr (uint32_t type, sector number, note: actual erase address = addr×4096) |
| Return Value | None |
W25Qxx_write
| Function Prototype | void W25Qxx_write(uint8_t* buffer, uint32_t addr, uint16_t numbyte) |
|---|---|
| Function Description | Write data to specified Flash address: first erase sector containing target address, send write enable, then send page write instruction (0x02) and address, finally continuously write numbyte bytes of data |
| Input Parameters | buffer (uint8_t * type, data source buffer to write) addr (uint32_t type, Flash target write address (24-bit)) numbyte (uint16_t type, total bytes to write) |
| Return Value | None |
W25Qxx_read
| Function Prototype | void W25Qxx_read(uint8_t* buffer, uint32_t read_addr, uint16_t read_length) |
|---|---|
| Function Description | Read data from specified Flash address: send read instruction (0x03) and target address, continuously read read_length bytes of data and store in buffer |
| Input Parameters | buffer (uint8_t * type, target buffer to store read data) read_addr (uint32_t type, Flash target read address (24-bit)) read_length (uint16_t type, total bytes to read) |
| Return Value | None |
OLED_Init
| Function Prototype | void OLED_Init(void) |
|---|---|
| Function Description | OLED initialization, execute SSD1306 initialization commands, clear screen and update display, set cursor default values, finally display "OLED init Success!" |
| Input Parameters | None |
| Return Value | None |
SSD1306_UpdateScreen
| Function Prototype | void SSD1306_UpdateScreen(void) |
|---|---|
| Function Description | OLED screen update display, loop write SSD1306_Buffer data to screen |
| Input Parameters | None |
| Return Value | None |
SSD1306_Fill
| Function Prototype | void SSD1306_Fill(SSD1306_COLOR_t color) |
|---|---|
| Function Description | OLED screen clear (not refreshed display), fill SSD1306_Buffer with all black or all white according to color |
| Input Parameters | color (SSD1306_COLOR_BLACK or SSD1306_COLOR_WHITE) |
| Return Value | None |
SSD1306_DrawPixel
| Function Prototype | void SSD1306_DrawPixel(uint16_t x, uint16_t y, SSD1306_COLOR_t color) |
|---|---|
| Function Description | Draw pixel at specified coordinates (x,y), set SSD1306_Buffer according to color and whether inverted |
| Input Parameters | x (horizontal coordinate), y (vertical coordinate), color (SSD1306_COLOR_BLACK or SSD1306_COLOR_WHITE) |
| Return Value | None |
SSD1306_GotoXY
| Function Prototype | void SSD1306_GotoXY(uint16_t x, uint16_t y) |
|---|---|
| Function Description | Set current cursor position |
| Input Parameters | x (horizontal coordinate), y (vertical coordinate) |
| Return Value | None |
SSD1306_Putc
| Function Prototype | char SSD1306_Putc(char ch, FontDef_t *Font, SSD1306_COLOR_t color) |
|---|---|
| Function Description | Draw single character, draw character at current cursor position according to font and color and update cursor |
| Input Parameters | ch (character to draw), Font (font structure pointer), color (character color) |
| Return Value | Return drawn character on success, return error character on failure |
SSD1306_Puts
| Function Prototype | char SSD1306_Puts(char *str, FontDef_t *Font, SSD1306_COLOR_t color) |
|---|---|
| Function Description | Draw string, call SSD1306_Putc one by one to draw each character in the string |
| Input Parameters | str (pointer to string to draw), Font (font structure pointer), color (character color) |
| Return Value | Return '\0' at end of string on success, return error character on failure |
OLED_ON
| Function Prototype | void OLED_ON(void) |
|---|---|
| Function Description | Wake OLED from sleep, send wake command |
| Input Parameters | None |
| Return Value | None |
OLED_OFF
| Function Prototype | void OLED_OFF(void) |
|---|---|
| Function Description | Put OLED to sleep (very low power consumption in sleep mode), send sleep command |
| Input Parameters | None |
| Return Value | None |
OLED_Clear
| Function Prototype | void OLED_Clear(void) |
|---|---|
| Function Description | OLED clear screen, call SSD1306_Fill to fill with black |
| Input Parameters | None |
| Return Value | None |
OLED_Refresh
| Function Prototype | void OLED_Refresh(void) |
|---|---|
| Function Description | Refresh OLED screen, call SSD1306_UpdateScreen |
| Input Parameters | None |
| Return Value | None |
OLED_Draw_String
| Function Prototype | void OLED_Draw_String(char *data, uint8_t x, uint8_t y, bool clear, bool refresh) |
|---|---|
| Function Description | Write characters, clear screen according to parameters, set cursor position to draw string, refresh screen |
| Input Parameters | data (string to display), x (horizontal coordinate), y (vertical coordinate), clear (whether to clear screen), refresh (whether to refresh) |
| Return Value | None |
OLED_Draw_Line
| Function Prototype | void OLED_Draw_Line(char *data, uint8_t line, bool clear, bool refresh) |
|---|---|
| Function Description | Write a line of characters, call OLED_Draw_String to display on corresponding line according to line number (1-3) |
| Input Parameters | data (string to display), line (line number, 1-3), clear (whether to clear screen), refresh (whether to refresh) |
| Return Value | None |
SSD1306_DrawLine
| Function Prototype | void SSD1306_DrawLine(uint16_t x0, uint16_t y0, uint16_t x1, uint16_t y1, SSD1306_COLOR_t c) |
|---|---|
| Function Description | Draw line segment, draw line segment between (x0,y0) to (x1,y1) |
| Input Parameters | x0 (start horizontal coordinate), y0 (start vertical coordinate), x1 (end horizontal coordinate), y1 (end vertical coordinate), c (line segment color) |
| Return Value | None |
VI. Experiment Phenomenon
After the program is flashed, it will run the flash self-test program, write "yahboom" to flash, then read flash content. If it is "yahboom", the OLED screen will display "Flash RDWT OK!"
