c - Printf output using UART in ARM Cortex-M3 microcontroller -

i have lpc1768 based board - landtiger (worth checking manual @ bottom). program use keil uvision4/72 lite , j-link edu segger. simple program interact joystick , diodes works fine, but...

i trying implement debug printf, can see printf output in keil "debug (printf) viewer" window. problem dont see output - think on right track because when run debugger can see trace:running @ bottom of window (before trace:no synchronization). unfortunately dont see in uart , debug output windows.

i've spent quite lot of time trying make work , appreciate help, thank ;)

my keil settings are:

project/options target/debug set j-link/j-trace cortex.

then inside it's settings have segger selected port:sw , max clock:10 mhz.

trace tab enabled 100mhz core clock , swo prescaler = 17 (which results in 5.882352mhz swo clock).

itm stimulus ports set enable:0xffffffff , privilege:0x0000000f

here parts of code:

define fosc 12000000

define fcclk (fosc * 8)

define fcco (fcclk * 3)

define fpclk (fcclk / 4)

define uart0_bps 115200

void uart0_init (void)

{

uint16_t usfdiv;

/* uart0 */

lpc_pincon->pinsel0 |= (1 << 4);/* pin p0.2 used txd0 (com0) */

lpc_pincon->pinsel0 |= (1 << 6);/* pin p0.3 used rxd0 (com0) */

lpc_uart0->lcr = 0x83;

usfdiv = (fpclk / 16) / uart0_bps;

lpc_uart0->dlm = usfdiv / 256;

lpc_uart0->dll = usfdiv % 256;

lpc_uart0->lcr = 0x03;

lpc_uart0->fcr = 0x06;
}

sending code:

int uart0_sendbyte (int ucdata)

{

while (!(lpc_uart0->lsr & 0x20)){};

return (lpc_uart0->thr = ucdata);

}

and fputc printf (it called - checked)

int fputc(int c, file *f)

{

if (c == '\n') {

uart0_sendbyte('\r');

}

return (uart0_sendbyte(c));

}

any ideas?

regards!

your fputc sends bytes directly uart, goes rs232 connector on board. if want see output of fputc, need connect cable between board , pc , see client such hyperterminal.

when talk trace capabilities, means adapter (j-link in case) creates high throughput communication between program , debugger , follows execution of program. there other debug functionalities. example if compile semihosting, program executes system calls (_write, _open, ...) intercepted debugger executes them on host machine.

so in experience either call printf, don't override fputc , compile semihosting, , expect output on debug window, or send uart, connect rs232 pc , see on hyperterminal.

i see found third method uses trace capabilities. believe semihosting option more general solution because can applied on setup doesn't have trace capabilities jtag (or swd) connection.