108 lines
2.6 KiB
C
108 lines
2.6 KiB
C
/**
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* Lab 2
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* This is configured with GPIO15 as a pseudo button with a pull up resistor
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* Since the button is active low, the program will send '1' when the button
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* is not pressed (high) and send 'A' to 'Z' when the button is pressed (low)
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*/
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#include <stdio.h>
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#include "pico/stdlib.h"
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#define UART_ID uart0
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#define BAUD_RATE 115200 // Baud rate of UART
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#define UART_TX_PIN 16 // GPIO for UART TX pin
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#define UART_RX_PIN 17 // GPIO for UART RX pin
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#define PSEUDO_BTN 15 // GPIO for pseudo button
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#define SLEEP_TIME 1000 // 1000ms is based on the lab requirements
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/**
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* Sends a character through UART0 based on the state of GPIO15 (Pseudo button)
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* @param uart_input Pointer to a character to be sent through UART0
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* @return void Prints the character in uart_receive()
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*/
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static void uart_transmit(u_char *uart_input) {
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if (gpio_get(PSEUDO_BTN))
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{
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uart_putc(UART_ID, '1');
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}
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else
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{
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uart_putc(UART_ID, *uart_input);
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// Increment character and wrap around if necessary
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*uart_input = (*uart_input - 'A' + 1) % 26 + 'A';
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}
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}
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/**
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* Receives a character through UART0 and prints it out
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* NOTE: Flipping bit 5 effectively converts a character to lowercase
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* EXAMPLE: 'A' = 0b01000001, 'a' = 0b01100001
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* @param uart_output Pointer to a location to store the received character
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* @return void Character is read and printed
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*/
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static void uart_receive(u_char *uart_output) {
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if (uart_is_readable(UART_ID))
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{
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*uart_output = uart_getc(UART_ID);
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if ((*uart_output >= 'A') && (*uart_output <= 'Z'))
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{
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*uart_output ^= (1 << 5); // This operation flips bit 5
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}
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else if (*uart_output == '1')
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{
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*uart_output = '2';
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}
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else
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{
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return;
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}
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printf("%c\n", *uart_output);
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}
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}
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/**
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* Initializes UART0 and GPIO pins
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* @return void
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*/
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static void pin_init() {
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// UART init
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uart_init(UART_ID, BAUD_RATE);
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gpio_set_function(UART_TX_PIN, GPIO_FUNC_UART);
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gpio_set_function(UART_RX_PIN, GPIO_FUNC_UART);
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// Disable UART FIFO for data to be tx/rx immediately
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uart_set_fifo_enabled(UART_ID, false);
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// Pseudo button init
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gpio_set_dir(PSEUDO_BTN, GPIO_IN);
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// Enable pull up resistor
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gpio_set_pulls(PSEUDO_BTN, true, false);
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}
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int main() {
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// Initialize stdio and pins first
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stdio_init_all();
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pin_init();
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u_char uart_input = 'A';
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u_char uart_output;
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while (1) {
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uart_transmit(&uart_input);
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uart_receive(&uart_output);
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sleep_ms(SLEEP_TIME);
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}
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}
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