为UART启用和测试本地环回

我正在尝试进行UART内部回路测试并提出以下更改

#include  #include  #include  #include  #include  #include  #include  #include  #include  #define CCSR_BASE 0xfe000000 #define UART1_BASE 0x11c000 #define UART1_LEN 0x1000 static volatile unsigned long *uartReg = MAP_FAILED; /* Map in registers. */ static unsigned long *initMapMem(int fd, unsigned long addr, unsigned long len) { return (unsigned long *) mmap(0, len, PROT_READ|PROT_WRITE|PROT_EXEC,MAP_SHARED|MAP_LOCKED, fd, addr); } int uartInitialise(void) { int fd; int i; fd = open("/dev/mem", O_RDWR | O_SYNC) ; if (fd < 0) { fprintf(stderr,"This program needs root privileges.Try sudo /n"); return -1; } uartReg = initMapMem(fd, ((CCSR_BASE) + (UART1_BASE)) , UART1_LEN); /* In local loop back mode, data written to UTHR(8 bit) can be read from the receiver buffer register(URBR 8 bit) of the same UART. */ // *(uartReg + 0x605 ) = 0x0; *(uartReg + (0x600)) = 0xf; printf("UART_REG : %#x\n", *(int *)(uartReg + (0x600)); /*Expecting 0xf to read here if loop back mode is set */ close(fd); if (uartReg == MAP_FAILED) { fprintf(stderr,"Bad, mmap failed\n"); return -1; } return 0; } int main() { int pins; int f = open( "/dev/ttyS1", O_RDWR); if (f< 0) { printf("\nout"); close(f); } ioctl( f, TIOCMGET, &pins); ioctl( f, TIOCMSET, pins | TIOCM_LOOP); if (uartInitialise() < 0) return 1; sleep(5); ioctl( f, TIOCMGET, &pins); ioctl( f, TIOCMSET, pins & ~ TIOCM_LOOP); } 

root @ amit：〜＃。/ loop_back

UART_REG：0

但是我没有得到预期的输出，任何人都可以指出需要做什么来进行UART内部回路测试？