135 lines
4.8 KiB
C
135 lines
4.8 KiB
C
/**
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* Simple USB Serial Echo Program with Timeout, Reconnect, and Backspace Logic.
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* This program now correctly handles the backspace character by deleting it
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* from the buffer and sending the necessary control codes to the terminal
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* for visual deletion.
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*/
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#include "pico/stdlib.h"
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#include "pico/time.h" // Needed for time_us_64()
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#include <stdio.h>
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#include <ctype.h>
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// Define the maximum size for the input string buffer
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#define MAX_INPUT_LEN 64
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// Define the timeout period: 1 second in microseconds
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#define TIMEOUT_US 5000000
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// ASCII code for Backspace (often sent as 0x08)
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#define ASCII_BACKSPACE 8
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// Helper function to handle the echoing and resetting of the buffer
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void echo_and_reset(char* buffer, int* index_ptr) {
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if (*index_ptr > 0) {
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// Null-terminate the string
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buffer[*index_ptr] = '\0';
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// Echo the string back, converting to uppercase
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printf("\nEchoed (ALL CAPS): ");
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for (int i = 0; buffer[i] != '\0'; i++) {
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printf("%c", toupper(buffer[i]));
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}
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printf("\n");
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}
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// Reset buffer for next line and print a new prompt
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*index_ptr = 0;
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printf("> ");
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}
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// Function to handle the initial waiting and reconnect waiting
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void wait_for_usb_connection() {
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printf("Waiting for USB host to connect...\n");
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// Wait until the USB host (e.g., terminal program) opens the serial port
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while (!stdio_usb_connected()) {
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sleep_ms(100);
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}
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// Connection established!
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printf("\nConnection Established! Starting Echo Session...\n");
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}
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void run_echo_session() {
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char input_buffer[MAX_INPUT_LEN];
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int buffer_index = 0;
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// Track the time (in microseconds) when the last character was received
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uint64_t last_char_time = time_us_64();
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printf("--- Pico USB String Echo Program Started ---\n");
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printf("Type a sentence (up to %d chars). It will echo on Enter/Timeout.\n", MAX_INPUT_LEN - 2);
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printf("--------------------------------------------\n");
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printf("> "); // Prompt for input
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// Inner loop runs ONLY while the USB connection is active
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while (stdio_usb_connected()) {
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// Check for incoming character without blocking
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int c = getchar_timeout_us(0);
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if (c != PICO_ERROR_TIMEOUT) {
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// Character received, update the timer
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last_char_time = time_us_64();
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char input_char = (char)c;
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// 1. --- BACKSPACE HANDLING ---
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if (input_char == ASCII_BACKSPACE || input_char == 127) { // 127 is sometimes sent by terminals (DEL key)
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if (buffer_index > 0) {
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// Decrease buffer index (remove the character)
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buffer_index--;
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// Send backspace, space, and backspace to erase the character on the terminal:
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// \b: move cursor back
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// ' ': overwrite with a space
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// \b: move cursor back again, ready for the next character
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printf("\b \b");
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}
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// 2. --- End of Input (Newline/CR) ---
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} else if (input_char == '\r' || input_char == '\n') {
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echo_and_reset(input_buffer, &buffer_index);
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// 3. --- Collect regular characters ---
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} else if (buffer_index < (MAX_INPUT_LEN - 1) && isprint(input_char)) {
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// Echo character locally so the user sees what they type
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printf("%c", input_char);
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// Store character in the buffer
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input_buffer[buffer_index] = input_char;
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buffer_index++;
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}
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// Ignore non-printable characters and overflowed buffer input
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}
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// 4. Timeout Check
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if (buffer_index > 0 && (time_us_64() - last_char_time) > TIMEOUT_US) {
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printf("\n--- Timeout Reached (5.0s silence) ---\n");
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echo_and_reset(input_buffer, &buffer_index);
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last_char_time = time_us_64(); // Reset time to prevent immediate re-trigger
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}
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// Add a small delay to prevent the loop from consuming too much CPU time
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sleep_us(100);
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}
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// Connection lost or closed by host
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printf("\nHost disconnected. Ending Echo Session.\n");
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}
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int main() {
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// Initialize Standard I/O (stdio) to use the USB backend
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stdio_init_all();
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// Outer loop: Allows the program to run continuously and restart the
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// session after a disconnection.
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while (true) {
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// 1. Wait for a connection
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wait_for_usb_connection();
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// 2. Run the program logic while connected
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run_echo_session();
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// Loop repeats, going back to wait_for_usb_connection()
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}
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// Note: main should not return
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} |