C8051f系列开发之keil c单步调试

C8051f系列单片机是一种高速，集成度很高的单片机，功能还是蛮强大的。我在用此款单片机读取ST 公司的三轴加速度计的时候发现输出总是全1。于是，我用keil c的单步调试功能。一步一步调试，于是我发现执行到一条把某一管脚置1的语句之后，watch窗口显示的相应管教状态仍是0.

于是我觉得可能是硬件的问题，引脚一直接地被拉低。果然，我在查看电路板的线路时发现sdi和sdo两根线与另外两个引脚相连，而这个连接是我修改版图时无意连接上的。而且一个引脚被配置成高电平，另外一个被配置成低电平。所以sdi和sdo都一直保持低电平和高电平。所以不能对传感器进行正常的配置和读取数据。

另附lis3lv02dq读取程序，采用的是虚拟spi总线。

#include "main.H"unsigned char spi_comm(unsigned char outgoing_byte){    uchar incoming_byte, x;    acc_spc = 1; //Pull SPI clock high    for(x = 0 ; x < 8 ; x++)    {    if(outgoing_byte&0x80)          acc_sdi =1; //Put bit on SPI data bus    else acc_sdi = 0;          outgoing_byte <<= 1; //Rotate byte 1 to the left        acc_spc = 0; //Toggle the SPI clock        acc_spc = 1;        incoming_byte <<= 1; //Rotate byte 1 to the leftif(acc_sdo)   //Read bit on SPI data bus       incoming_byte += 0x01;            }        return(incoming_byte);}unsigned char read_register(unsigned char register_name){    uchar in_byte;        register_name |= 0x80; //Set D7 to 1 for read mode   acc_cs = 0; //Select LIS    in_byte = spi_comm(register_name); //SPI read 6-bit register from LIS    //printf("In1 = %h ", in_byte);        //in_byte is nothing, we need to clock in another 8 bits    in_byte = spi_comm(0x00); //Send nothing, but we should get back the register value        acc_cs = 1;        return(in_byte);}//Sends a write command to LISvoid write_register(unsigned char register_name, unsigned char register_value){    unsigned char in_byte;        register_name &= 0x7f; //Clear D7 to 0 for write mode    acc_cs = 0; //Select LIS    in_byte = spi_comm(register_name); //SPI read 6-bit register from LIS    //printf("In1 = %h ", in_byte);        //in_byte is nothing, we need to clock in the value to write    in_byte = spi_comm(register_value); //Send nothing, but we should get back the register value        acc_cs = 1;        //Return nothing}   void acc_spi(void) {    acc_cs = 1; //Unselect LIS   // CK = 0;  // acc[0] = read_register(0x0F); //Read register WHO_AM_I       write_register(0x20,0xc7); //Power on device, enable all axis, and turn off self test - CTRL_REG1    delay(5); write_register(0x21,0x44);while(!acc_rdy);         acc[1] = read_register(0x28); //Read outx_l    acc[0] = read_register(0x29); //Read outx_hacc[3] = read_register(0x2a);acc[2] = read_register(0x2b);acc[5] = read_register(0x2c);acc[4] = read_register(0x2d);             }