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本文主要介绍RT-thread中的SPI设备驱动，涉及到的文件主要有：spi_dev.c，spi_core.c，spi.h，spi_hard.c，spi_hard.h。
一、SPI设备框架
先来看spi.h中的一些数据结构：
** * SPI message structure */ struct rt_spi_message { const void *send_buf; void *recv_buf; rt_size_t length; struct rt_spi_message *next; unsigned cs_take : 1; unsigned cs_release : 1; }; /** * SPI configuration structure */ struct rt_spi_configuration { rt_uint8_t mode; rt_uint8_t data_width; rt_uint16_t reserved; rt_uint32_t max_hz; }; struct rt_spi_ops; struct rt_spi_bus { struct rt_device parent; const struct rt_spi_ops *ops; struct rt_mutex lock; struct rt_spi_device *owner; }; /** * SPI operators */ struct rt_spi_ops { rt_err_t (*configure)(struct rt_spi_device *device, struct rt_spi_configuration *configuration); rt_uint32_t (*xfer)(struct rt_spi_device *device, struct rt_spi_message *message); };
/** * SPI Virtual BUS, one device must connected to a virtual BUS */ struct rt_spi_device { struct rt_device parent; struct rt_spi_bus *bus; struct rt_spi_configuration config; }; #define SPI_DEVICE(dev) ((struct rt_spi_device *)(dev))
spi_core.c,spi_dev.c这两个文件位于RTT\components\drivers\spi目录下，而spi.h头文件位于RTT\\components\drivers\include\drivers目录下。可在MKD工程的Drivers组下将上面两个源文件加进行，并将spi.h头文件所在目录添加到工程的include path下。
spi_core.c文件实现了spi的抽象操作，如注册spi总线(spi_bus)，向SPI总线添加设备函数等。注: 这里将MCU的一路spi外设虚拟成spi总线，然后总线上可以挂很多spi设备(spi_device)，一个spi_device有一个片选cs。spi总线和spi设备要在RTT中可以生效就必须先向RTT注册,因此就需要使用上面的注册SPI总线函数和向SPI总线中添加SPI设备。
spi_core.c还包含了配置SPI函数，发送和接收等通信函数，占用和释放SPI总线函数及选择SPI设备函数。这些函数都是抽象出来的，反映出SPI总线上的一些常规操作。真正执行这些操作的过程并不在spi_core.c源文件中，实际上，这些操作信息都是通过注册SPI总线和向总线添加SPI设备时这些操作集就已经"注册"下来了，真正操作时是通过注册信息内的操作函数去实现,也可以说是一种回调操作。spi_core.c中实现的函数主要有：rt_spi_bus_register(); rt_spi_bus_attach_device(); rt_spi_configure(); rt_spi_send_then_send(); rt_spi_send_then_recv(); rt_spi_transfer(); rt_spi_transfer_message(); rt_spi_take_bus(); rt_spi_release_bus(); rt_spi_take(); rt_spi_release()。
而spi_dev.c实现了SPI设备的一些抽象操作，比如读，写，打开，关闭，初始化等，当然当MCU操作SPI设备的时候，是需要通过SPI总线与SPI设备进行通信的，既然通信就必然会有SPI通信协议，但是通信协议并不在这里具体，spi_dev.c这里还只是SPI设备的抽象操作而已，它只是简单地调用spi_core.c源文件中的抽象通信而已，具体实现还是要靠上层通过SPI总线或SPI设备注册下来的信息而实现的。spi_device.c中实现的函数主要有:_spi_bus_device_read(); _spi_bus_device_write(); _spi_bus_device_control(); rt_spi_bus_device_init();_spidev_device_read();_spidev_device_write();_spidev_device_control();rt_spidev_device_init()。
在确保了spi_core.c，spi_dev.c和spi.h这三个源文件在MDK工程内之后，接着往下走。
二、SPI底层硬件驱动
在spi_hard.c中实现configure和xfer函数：
static struct rt_spi_ops stm32_spi_ops = { configure, xfer };
然后，向RT-thread注册spi总线：
struct stm32_spi_bus { struct rt_spi_bus parent; SPI_TypeDef * SPI; #ifdef SPI_USE_DMA DMA_Stream_TypeDef * DMA_Stream_TX; uint32_t DMA_Channel_TX; DMA_Stream_TypeDef * DMA_Stream_RX; uint32_t DMA_Channel_RX; uint32_t DMA_Channel_TX_FLAG_TC; uint32_t DMA_Channel_RX_FLAG_TC; #endif /* #ifdef SPI_USE_DMA */ }; struct stm32_spi_cs { GPIO_TypeDef * GPIOx; uint16_t GPIO_Pin; };
rt_err_t stm32_spi_register(SPI_TypeDef * SPI, struct stm32_spi_bus * stm32_spi, const char * spi_bus_name) { if(SPI == SPI1) { stm32_spi->SPI = SPI1; RCC_APB2PeriphClockCmd(RCC_APB2Periph_SPI1, ENABLE);//84MHZ #ifdef SPI_USE_DMA RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_DMA2, ENABLE); /* DMA2_Stream0 DMA_Channel_3 : SPI1_RX ; DMA2_Stream2 DMA_Channel_3 : SPI1_RX */ stm32_spi->DMA_Stream_RX = DMA2_Stream0; stm32_spi->DMA_Channel_RX = DMA_Channel_3; stm32_spi->DMA_Channel_RX_FLAG_TC = DMA_FLAG_TCIF0; /* DMA2_Stream3 DMA_Channel_3 : SPI1_TX ; DMA2_Stream5 DMA_Channel_3 : SPI1_TX */ stm32_spi->DMA_Stream_TX = DMA2_Stream3; stm32_spi->DMA_Channel_TX = DMA_Channel_3; stm32_spi->DMA_Channel_TX_FLAG_TC = DMA_FLAG_TCIF3; #endif } else if(SPI == SPI2) { stm32_spi->SPI = SPI2; RCC_APB1PeriphClockCmd(RCC_APB1Periph_SPI2, ENABLE);//42MHZ #ifdef SPI_USE_DMA RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_DMA1, ENABLE); /* DMA1_Stream3 DMA_Channel_0 : SPI2_RX */ stm32_spi->DMA_Stream_RX = DMA1_Stream3; stm32_spi->DMA_Channel_RX = DMA_Channel_0; stm32_spi->DMA_Channel_RX_FLAG_TC = DMA_FLAG_TCIF3; /* DMA1_Stream4 DMA_Channel_0 : SPI2_TX */ stm32_spi->DMA_Stream_TX = DMA1_Stream4; stm32_spi->DMA_Channel_TX = DMA_Channel_0; stm32_spi->DMA_Channel_TX_FLAG_TC = DMA_FLAG_TCIF4; #endif } else if(SPI == SPI3) { stm32_spi->SPI = SPI3; RCC_APB1PeriphClockCmd(RCC_APB1Periph_SPI3, ENABLE);//42MHZ #ifdef SPI_USE_DMA RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_DMA1, ENABLE); /* DMA1_Stream2 DMA_Channel_0 : SPI3_RX ; DMA1_Stream0 DMA_Channel_0 : SPI3_RX */ stm32_spi->DMA_Stream_RX = DMA1_Stream2; stm32_spi->DMA_Channel_RX = DMA_Channel_0; stm32_spi->DMA_Channel_RX_FLAG_TC = DMA_FLAG_TCIF2; /* DMA1_Stream5 DMA_Channel_0 : SPI3_TX ; DMA1_Stream7 DMA_Channel_0 : SPI3_TX */ stm32_spi->DMA_Stream_TX = DMA1_Stream5; stm32_spi->DMA_Channel_TX = DMA_Channel_0; stm32_spi->DMA_Channel_TX_FLAG_TC = DMA_FLAG_TCIF5; #endif } else { return RT_ENOSYS; } return rt_spi_bus_register(&stm32_spi->parent, spi_bus_name, &stm32_spi_ops); }
最后，进行spi硬件初始化，并挂载spi设备到已注册的spi总线。
int rt_hw_spi1_init(void) { /* register SPI bus */ static struct stm32_spi_bus stm32_spi; //it must be add static /* SPI1 configure */ { GPIO_InitTypeDef GPIO_InitStructure; /* Enable GPIO Periph clock */ RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOA , ENABLE); GPIO_PinAFConfig(GPIOA, GPIO_PinSource5, GPIO_AF_SPI1); GPIO_PinAFConfig(GPIOA, GPIO_PinSource6, GPIO_AF_SPI1); GPIO_PinAFConfig(GPIOA, GPIO_PinSource7, GPIO_AF_SPI1); GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF; GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz; GPIO_InitStructure.GPIO_OType = GPIO_OType_PP; GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_NOPULL; /* Configure SPI1 pins */ GPIO_InitStructure.GPIO_Pin = GPIO_Pin_5; GPIO_Init(GPIOA, &GPIO_InitStructure); GPIO_InitStructure.GPIO_Pin = GPIO_Pin_6; GPIO_Init(GPIOA, &GPIO_InitStructure); GPIO_InitStructure.GPIO_Pin = GPIO_Pin_7; GPIO_Init(GPIOA, &GPIO_InitStructure); } /* SPI1 configuration */ /* register SPI1 to stm32_spi_bus */ stm32_spi_register(SPI1, &stm32_spi, "spi1"); /* attach spi10 */ { static struct rt_spi_device rt_spi_device_10; //it must be add static static struct stm32_spi_cs stm32_spi_cs_10; //it must be add static stm32_spi_cs_10.GPIOx = GPIOE; stm32_spi_cs_10.GPIO_Pin = GPIO_Pin_3; RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOE, ENABLE); GPIO_InitTypeDef GPIO_InitStructure; GPIO_InitStructure.GPIO_Mode = GPIO_Mode_OUT; GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz; GPIO_InitStructure.GPIO_OType = GPIO_OType_PP; GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_NOPULL; GPIO_InitStructure.GPIO_Pin = GPIO_Pin_3; GPIO_Init(GPIOE, &GPIO_InitStructure); GPIO_SetBits(GPIOE, GPIO_Pin_3); rt_spi_bus_attach_device(&rt_spi_device_10, "spi10", "spi1", (void*)&stm32_spi_cs_10);//set spi_device->bus /* config spi */ { struct rt_spi_configuration cfg; cfg.data_width = 8; cfg.mode = RT_SPI_MODE_3 | RT_SPI_MSB; /* SPI Compatible Modes 3 and SPI_FirstBit_MSB in lis302dl datasheet */ //APB2=168M/2=84M, SPI1 = 84/2,4,8,16,32 = 42M, 21M, 10.5M, 5.25M, 2.625M ... cfg.max_hz = 2625000; /* SPI_BaudRatePrescaler_16=84000000/16=5.25MHz. The max_hz of lis302dl is 10MHz in datasheet */ rt_spi_configure(&rt_spi_device_10, &cfg); } /* config spi */ } /* attach spi10 */ return 0; } INIT_BOARD_EXPORT(rt_hw_spi1_init);//rt_hw_spi1_init will be called in rt_components_board_init()
三、SPI设备初始化
这里以lis302dl三轴加速度计为例：
static rt_err_t lis302dl_init(const char * spi_device_name) { rt_uint8_t chip_id, ctrl, temp; spi_device = (struct rt_spi_device *)rt_device_find(spi_device_name); if(spi_device == RT_NULL) { rt_kprintf("\nspi_device %s for lis302dl not found!\n", spi_device_name); return -RT_ENOSYS; } // /* If not use rt_device_write or rt_device_read, then it‘s no necessary to rt_device_open */ // /* oflag has no meaning for spi device , so set to RT_NULL */ // if(rt_device_open(&spi_device->parent, RT_NULL) != RT_EOK) // { // rt_kprintf("\nspi_device %s for lis302dl opened failed!\n", spi_device_name); // return -RT_EEMPTY; // } LIS302DL_InitTypeDef LIS302DL_InitStruct; LIS302DL_FilterConfigTypeDef LIS302DL_FilterStruct; /* Set configuration of LIS302DL*/ LIS302DL_InitStruct.Output_DataRate = LIS302DL_DATARATE_100; LIS302DL_InitStruct.Power_Mode = LIS302DL_LOWPOWERMODE_ACTIVE; LIS302DL_InitStruct.Full_Scale = LIS302DL_FULLSCALE_2_3; LIS302DL_InitStruct.Self_Test = LIS302DL_SELFTEST_NORMAL; LIS302DL_InitStruct.Axes_Enable = LIS302DL_XYZ_ENABLE; LIS302DL_Init(&LIS302DL_InitStruct); /* MEMS High Pass Filter configuration */ LIS302DL_FilterStruct.HighPassFilter_Data_Selection = LIS302DL_FILTEREDDATASELECTION_OUTPUTREGISTER; LIS302DL_FilterStruct.HighPassFilter_Interrupt = LIS302DL_HIGHPASSFILTERINTERRUPT_1_2; LIS302DL_FilterStruct.HighPassFilter_CutOff_Frequency = LIS302DL_HIGHPASSFILTER_LEVEL_1; LIS302DL_FilterConfig(&LIS302DL_FilterStruct); /* not use internal high pass filter and INT2 */ ctrl=0x04;//enable INT1 Data ready interrupt; interrupt active high; pull-push; LIS302DL_Write(&ctrl, LIS302DL_CTRL_REG3_ADDR, 1); LIS302DL_Read(&temp, LIS302DL_CTRL_REG3_ADDR, 1); if(temp == ctrl) rt_kprintf("the LIS302DL_CTRL_REG3_ADDR(value 0x%02x) verify passed!\n", temp); else rt_kprintf("the LIS302DL_CTRL_REG3_ADDR(value 0x%02x) verify failed!\n", temp); /* Required delay for the MEMS Accelerometre: Turn-on time = 3/Output data Rate = 3/100 = 30ms in datasheet */ //rt_thread_delay(30); extern void stm32_mdelay(rt_uint32_t ms); stm32_mdelay(30); /* power_mode is active */ LIS302DL_Read(&chip_id, LIS302DL_WHO_AM_I_ADDR, 1); rt_kprintf("(chip_id of lis302dl is 0x%02x)", chip_id); return 0; } int rt_lis302dl_init(void) { rt_sem_init(&sem_lis302dl, "lis302dl", 0, RT_IPC_FLAG_FIFO); lis302dl_interrupt_int1(); lis302dl_init("spi10"); return 0; } INIT_APP_EXPORT(rt_lis302dl_init);
注：
1、若需要使用rt_device_read()或rt_device_write()函数，则必须先调用rt_device_open()打开spi设备，保证该设备的ref_count大于0。硬件初始化函数中不需要调用rt_device_open()打开spi总线，因为在rt_spi_bus_attach_device()函数中没有初始化bus->owner，从而会导致调用_spi_bus_device_read()或_spi_bus_device_write()时“RT_ASSERT(bus->owner != RT_NULL);”断言语句进入死循环。而 _spidev_device_read()或_spidev_device_write()中断言语句“RT_ASSERT(device->bus != RT_NULL);”正常通过。
2、在使用SPI设备驱动操作数字芯片的寄存器时，需谨慎使用rt_device_read()和rt_device_write()函数。因为根据spi读写时序，spi读写一次最少要连续操作2个字节数据（第一个为寄存器地址值，第二个为待读取或待写入的字节数据），并且在这2个字节数据之间CS信号不能拉高，而rt_device_read()和rt_device_write()函数仅操作一个字节后，cs信号拉高，导致字节数据不能正常读取或写入相应寄存器。所以，一般情况下在SPI工作在全双工模式时，读写数字芯片寄存器的函数中直接使用spi_core.c中的rt_spi_transfer()、rt_spi_send_then_recv()、rt_spi_send_then_send()三个函数，如下所示：
void LIS302DL_Write(rt_uint8_t* pBuffer, rt_uint8_t WriteAddr, rt_uint16_t NumByteToWrite) { /* Configure the MS bit: - When 0, the address will remain unchanged in multiple read/write commands. - When 1, the address will be auto incremented in multiple read/write commands. */ if(NumByteToWrite > 0x01) { WriteAddr |= (rt_uint8_t)MULTIPLEBYTE_CMD; } /* the CS can‘t pull up between &WriteAddr and pBuffer */ //rt_device_write(&spi_device->parent, RT_NULL, &WriteAddr, 1); //rt_device_write(&spi_device->parent, RT_NULL, pBuffer, NumByteToWrite); rt_spi_send_then_send(spi_device, &WriteAddr, 1, pBuffer, NumByteToWrite);// transfer NumByteToWrite+1 bytes } void LIS302DL_Read(rt_uint8_t* pBuffer, rt_uint8_t ReadAddr, rt_uint16_t NumByteToRead) { /* Configure the MS bit: - When 0, the address will remain unchanged in multiple read/write commands. - When 1, the address will be auto incremented in multiple read/write commands. */ if(NumByteToRead > 0x01) { ReadAddr |= (rt_uint8_t)(READWRITE_CMD | MULTIPLEBYTE_CMD); } else { ReadAddr |= (rt_uint8_t)READWRITE_CMD; } /* the CS can‘t pull up between &WriteAddr and pBuffer */ //rt_device_write(&spi_device->parent, RT_NULL, &ReadAddr, 1); //rt_device_read(&spi_device->parent, RT_NULL, pBuffer, NumByteToRead); rt_spi_send_then_recv(spi_device, &ReadAddr, 1, pBuffer, NumByteToRead);// transfer NumByteToRead+1 bytes }
3、对于可读取寄存器值的数字芯片，在写入字节数据后可通过读取相同寄存器，判断读出的值与写入的值是否一致，从而判断寄存器写操作是否正确，如下：
void LIS302DL_Init(LIS302DL_InitTypeDef *LIS302DL_InitStruct) { rt_uint8_t ctrl = 0x00; /* Configure MEMS: data rate, power mode, full scale, self test and axes */ ctrl = (rt_uint8_t) (LIS302DL_InitStruct->Output_DataRate | LIS302DL_InitStruct->Power_Mode | LIS302DL_InitStruct->Full_Scale | LIS302DL_InitStruct->Self_Test | LIS302DL_InitStruct->Axes_Enable); /* Write value to MEMS CTRL_REG1 regsister */ LIS302DL_Write(&ctrl, LIS302DL_CTRL_REG1_ADDR, 1); rt_uint8_t temp = 0x00; LIS302DL_Read(&temp, LIS302DL_CTRL_REG1_ADDR, 1); if(temp == ctrl) rt_kprintf("\nthe LIS302DL_CTRL_REG1_ADDR(value 0x%02x) verify passed!\n", temp); else rt_kprintf("\nthe LIS302DL_CTRL_REG1_ADDR(value 0x%02x) verify failed!\n", temp); }
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原文地址：http://www.cnblogs.com/King-Gentleman/p/4657844.html
