Had to try it with two serial interrupt routines (TX,RX) with circular buffers. Uses sprintf and reads back with sscanf in a loop checking for the same number. Seems solid and never locks up, but I could spend a bit more time double checking buffer conditions.
#include "mbed.h"
// Serial TX & RX interrupt loopback test using formatted IO - sprintf and sscanf
// Connect TX to RX (p9 to p10)
// or can also use USB and type back in the number printed out in a terminal window
// Sends out ASCII numbers in a loop and reads them back
// If not the same number LED4 goes on
// LED1 and LED2 indicate RX and TX interrupt routine activity
// LED3 changing indicate main loop running
Serial device(p9, p10); // tx, rx
// Can also use USB and type back in the number printed out in a terminal window
// Serial monitor_device(USBTX, USBRX);
DigitalOut led1(LED1);
DigitalOut led2(LED2);
DigitalOut led3(LED3);
DigitalOut led4(LED4);
void Tx_interrupt();
void Rx_interrupt();
void send_line();
void read_line();
// Circular buffers for serial TX and RX data - used by interrupt routines
const int buffer_size = 255;
char tx_buffer[buffer_size];
char rx_buffer[buffer_size];
// Circular buffer pointers
volatile int tx_in=0;
volatile int tx_out=0;
volatile int rx_in=0;
volatile int rx_out=0;
// Line buffers for sprintf and sscanf
char tx_line[80];
char rx_line[80];
// main test program
int main() {
int i=0;
int rx_i=0;
device.baud(9600);
// Setup a serial interrupt function to receive data
device.attach(&Rx_interrupt, Serial::RxIrq);
// Setup a serial interrupt function to transmit data
device.attach(&Tx_interrupt, Serial::TxIrq);
// Formatted IO test using send and receive serial interrupts
// with sprintf and sscanf
while (1) {
// Loop to generate different test values - send value in hex, decimal, and octal and then read back
for (i=0; i<0xFFFF; i++) {
led3=1;
// Print ASCII number to tx line buffer in hex
sprintf(tx_line,"%x\r\n",i);
// Copy tx line buffer to large tx buffer for tx interrupt routine
send_line();
// Print ASCII number to tx line buffer in decimal
sprintf(tx_line,"%d\r\n",i);
// Copy tx line buffer to large tx buffer for tx interrupt routine
send_line();
// Print ASCII number to tx line buffer in octal
sprintf(tx_line,"%o\r\n",i);
// Copy tx line buffer to large tx buffer for tx interrupt routine
send_line();
led3=0;
// Read a line from the large rx buffer from rx interrupt routine
read_line();
// Read ASCII number from rx line buffer
sscanf(rx_line,"%x",&rx_i);
// Check that numbers are the same
if (i != rx_i) led4=1;
// Read a line from the large rx buffer from rx interrupt routine
read_line();
// Read ASCII number from rx line buffer
sscanf(rx_line,"%d",&rx_i);
// Check that numbers are the same
if (i != rx_i) led4=1;
// Read a line from the large rx buffer from rx interrupt routine
read_line();
// Read ASCII number from rx line buffer
sscanf(rx_line,"%o",&rx_i);
// Check that numbers are the same
if (i != rx_i) led4=1;
}
}
}
// Copy tx line buffer to large tx buffer for tx interrupt routine
void send_line() {
int i;
char temp_char;
bool empty;
i = 0;
// Start Critical Section - don't interrupt while changing global buffer variables
NVIC_DisableIRQ(UART1_IRQn);
empty = (tx_in == tx_out);
while ((i==0) || (tx_line[i-1] != '\n')) {
// Wait if buffer full
if (((tx_in + 1) % buffer_size) == tx_out) {
// End Critical Section - let interrupt routine empty buffer by sending
NVIC_EnableIRQ(UART1_IRQn);
while (((tx_in + 1) % buffer_size) == tx_out) {
}
// Start Critical Section - don't interrupt while changing global buffer variables
NVIC_DisableIRQ(UART1_IRQn);
}
tx_buffer[tx_in] = tx_line[i];
i++;
tx_in = (tx_in + 1) % buffer_size;
}
if (device.writeable() && (empty)) {
temp_char = tx_buffer[tx_out];
tx_out = (tx_out + 1) % buffer_size;
// Send first character to start tx interrupts, if stopped
device.putc(temp_char);
}
// End Critical Section
NVIC_EnableIRQ(UART1_IRQn);
return;
}
// Read a line from the large rx buffer from rx interrupt routine
void read_line() {
int i;
i = 0;
// Start Critical Section - don't interrupt while changing global buffer variables
NVIC_DisableIRQ(UART1_IRQn);
// Loop reading rx buffer characters until end of line character
while ((i==0) || (rx_line[i-1] != '\r')) {
// Wait if buffer empty
if (rx_in == rx_out) {
// End Critical Section - to allow rx interrupt to get new characters for buffer
NVIC_EnableIRQ(UART1_IRQn);
while (rx_in == rx_out) {
}
// Start Critical Section - don't interrupt while changing global buffer variables
NVIC_DisableIRQ(UART1_IRQn);
}
rx_line[i] = rx_buffer[rx_out];
i++;
rx_out = (rx_out + 1) % buffer_size;
}
rx_line[i-1] = 0;
// End Critical Section
NVIC_EnableIRQ(UART1_IRQn);
return;
}
// Interupt Routine to read in data from serial port
void Rx_interrupt() {
led1=1;
// Loop just in case more than one character is in UART's receive FIFO buffer
// Stop if buffer full
while ((device.readable()) || (((rx_in + 1) % buffer_size) == rx_out)) {
rx_buffer[rx_in] = device.getc();
// Uncomment to Echo to USB serial to watch data flow
// monitor_device.putc(rx_buffer[rx_in]);
rx_in = (rx_in + 1) % buffer_size;
}
led1=0;
return;
}
// Interupt Routine to write out data to serial port
void Tx_interrupt() {
led2=1;
// Loop to fill more than one character in UART's transmit FIFO buffer
// Stop if buffer empty
while ((device.writeable()) && (tx_in != tx_out)) {
device.putc(tx_buffer[tx_out]);
tx_out = (tx_out + 1) % buffer_size;
}
led2=0;
return;
}
jim hamblen.
27
replies
Willem Melching wrote:
Hi,
I want to make a robot with a couple of sensors and an xbee module connected to the 3 uarts. The compass sensor and the xbee modules only send messages shorter than 16 characters, so the messages fit in the uart buffer. So I can read them when it suits me. But i have a problem with the gps module. This module sends a lot of data, and only a small part is interesting. Every second it sends a couple of lines:
This is some sample data i have found on the internet, my module does like 5 of these strings. But the only interesting thing is this:
3409.0533,N,11817.0188,W
What is the best way to capture this data? I can't check the buffer in a while loop in the main code. My code is busy with a PID controller and a lot of floating point calculations.