[经验] DSP28335外接DAC8554教程

1175722741 2016-5-30 15:55 楼主

DAC8554芯片的数据传输接口为SPI，每一帧为24位；但是28335的SPI接口最高可配置为16位。

使用28335控制DAC8554方法有三种：

1.才用IO口模拟SPI接口通信；

2.灵活使用28335的SPI接口通信；

3.使用28335的McBSP接口按照DAC8554的时序自定义通信格式。

此处以第二种方法为例：

dsp28335与DAC8554的接线为：

DAC8554的写时序为：

/SYNC必须在D_IN发送24位后DAC才认为接收到的数据为有效数据，否则，将接收到的数据舍弃。

本实验所使用的具体方法是开启28335SPI的FIFO功能，将24位数据帧分成两个12位的数据，依次存入SPITXBUF，这样就可以spi成功发送24的帧

#include "DSP2833x_Device.h" // DSP2833x Headerfile Include File
#include "DSP2833x_Examples.h" // DSP2833x Examples Include File
#define spi_socket 0x10//OUTA
void spi_fifo_init(void);
void spi_init(void);
void spi_xmit(Uint16 a);
void main(void)
{
float sdata; // send data
// Step 1. Initialize System Control:
// PLL, WatchDog, enable Peripheral Clocks
// This example function is found in the DSP2833x_SysCtrl.c file.
InitSysCtrl();
// Step 2. Initalize GPIO:
// This example function is found in the DSP2833x_Gpio.c file and
// illustrates how to set the GPIO to it's default state.
// InitGpio(); // Skipped for this example
// Setup only the GP I/O only for SPI-A functionality
// This function is found in DSP2833x_Spi.c
InitXintf16Gpio(); //zq
InitSpiaGpio();
// Step 3. Clear all interrupts and initialize PIE vector table:
// Disable CPU interrupts
DINT;
// Initialize PIE control registers to their default state.
// The default state is all PIE interrupts disabled and flags
// are cleared.
// This function is found in the DSP2833x_PieCtrl.c file.
InitPieCtrl();
// Disable CPU interrupts and clear all CPU interrupt flags:
IER = 0x0000;
IFR = 0x0000;
// Initialize the PIE vector table with pointers to the shell Interrupt
// Service Routines (ISR).
// This will populate the entire table, even if the interrupt
// is not used in this example. This is useful for debug purposes.
// The shell ISR routines are found in DSP2833x_DefaultIsr.c.
// This function is found in DSP2833x_PieVect.c.
InitPieVectTable();
// Step 4. Initialize all the Device Peripherals:
// This function is found in DSP2833x_InitPeripherals.c
// InitPeripherals(); // Not required for this example
spi_fifo_init(); // Initialize the Spi FIFO
spi_init(); // init SPI
// Step 5. User specific code:
// Transmit data
sdata=sdata*198.6;// 变比为100/1
spi_xmit(sdata);
}
// Step 7. Insert all local Interrupt Service Routines (ISRs) and functions here:
void spi_init()
{
SpiaRegs.SPICCR.all =0x000B; // Reset on, rising edge, 12-bit char bits
SpiaRegs.SPICTL.all =0x0006; // Enable master mode, normal phase,
// enable talk, and SPI int disabled.
SpiaRegs.SPIBRR =0x0004;//150M/2/(SPIBRR+1)=15M
SpiaRegs.SPICCR.all =0x009B; // Relinquish SPI from Reset
SpiaRegs.SPIPRI.bit.FREE = 1; // Set so breakpoints don't disturb xmission
}
void spi_xmit(Uint16 a)
{
SpiaRegs.SPITXBUF=(((spi_socket<<8)&0xff00)|((a>>8)&0x00ff));
SpiaRegs.SPITXBUF=(a<<4);
}
void spi_fifo_init()
{
// Initialize SPI FIFO registers
SpiaRegs.SPIFFTX.all=0xE040;
SpiaRegs.SPIFFRX.all=0x204f;
SpiaRegs.SPIFFCT.all=0x0;
}
//===========================================================================
// No more.
//===========================================================================