Complete Listing Of Web Server

The following listing also includes all of the functions presented in the chapter even if they aren’t used.

#include <stdio.h>
#include "pico/stdlib.h"
#include "hardware/gpio.h"
#include <string.h>
#define Debug true
int initWiFi()
{
    uart_init(uart1, 115200);
    gpio_set_function(4, GPIO_FUNC_UART);
    gpio_set_function(5, GPIO_FUNC_UART);
    uart_set_format(uart1, 8, 1, UART_PARITY_NONE);
    uart_set_translate_crlf(uart1, true);
    sleep_ms(100);
    return 0;
}

int getBlock(uint8_t buf[], int len)
{
    int count = 0;
    while (count < len - 1)
    {
        if (uart_is_readable_within_us(uart1, 10000))
        {
            buf[count++] = uart_getc(uart1);
            if (Debug)
                uart_putc(uart0, buf[count - 1]);
        }
        else
        {
            break;
        }
    }
    buf[count] = 0;
    return count;
}

int ATWiFi(uint8_t buf[], int len)
{
    uint8_t SendData[] = "AT\r\n";
    uart_write_blocking(uart1, SendData, 4);
    return getBlock(buf, len);
}

int getVersionWiFi(uint8_t buf[], int len)
{
    uint8_t SendData[] = "AT+GMR\r\n";
    uart_write_blocking(uart1, SendData, 8);
    return getBlock(buf, len);
}

int resetWiFi(uint8_t buf[], int len)
{
    uint8_t SendData[] = "AT+RST\r\n";
    uart_write_blocking(uart1, SendData, 8);
    return getBlock(buf, len);
}

int setUARTWiFi(uint8_t buf[], int len)
{
    uint8_t SendData[] =
            "AT+UART_CUR=115200,8,1,0,0\r\n";
    uart_write_blocking(uart1, SendData, 28);
    return getBlock(buf, len);
}

int modeWiFi(uint8_t buf[], int len, int mode)
{
    uint8_t command[32];
    int count = snprintf(command, 32, 
                 "AT+CWMODE_CUR=%d\r\n", mode);
    uart_write_blocking(uart1, command, count);
    return getBlock(buf, len);
}

int getBlocks(uint8_t buf[], int len, int num, 
                                      char target[])
{
    for (int i = 0; i < num; i++)
    {
        if (uart_is_readable_within_us(uart1,
                                      1000 * 1000))
        {
            getBlock(buf, len);
            if (strstr(buf, target))
                return i;
        }
    }
    return -1;
}

int scanWiFi(uint8_t buf[], int len)
{
    uint8_t SendData[] = "AT+CWLAP\r\n";
    uart_write_blocking(uart1, SendData, 18);
    return getBlocks(buf, len, 20, "OK");
}

int connectWiFi(uint8_t buf[], int len, char ssid[],
                                  char pass[])
{
    uint8_t command[128];
    int count = snprintf(command, 128, 
          "AT+CWJAP_CUR=\"%s\",\"%s\"\r\n", ssid, pass);
    uart_write_blocking(uart1, command, count);
    return getBlocks(buf, len, 20, "OK");
}

int getIPWiFi(uint8_t buf[], int len)
{
    uint8_t SendData[] = "AT+CIFSR\r\n";
    uart_write_blocking(uart1, SendData, 10);
    return getBlocks(buf, len, 20, "OK");
}

int getWebPageWiFi(uint8_t buf[], int len, 
                             char URL[], char page[])
{
    uint8_t command[128];
    int count = snprintf(command, 128,
             "AT+CIPSTART=\"TCP\",\"%s\",80\r\n", URL);
    uart_write_blocking(uart1, command, count);
    if (getBlocks(buf, len, 20, "OK") < 0)
        return -1;
    char http[150];
    sprintf(http, "GET %s HTTP/1.1\r\n
             Host:%s\r\n\r\n", page, URL);
    count = snprintf(command, 128,
                  "AT+CIPSEND=%d\r\n", strlen(http));
    uart_write_blocking(uart1, command, count);
    if (getBlocks(buf, len, 20, ">") < 0)
        return -1;
    uart_write_blocking(uart1, http, strlen(http));
    return getBlocks(buf, len, 20, "</html>");
}

int startServerWiFi(uint8_t buf[], int len)
{
    char temp[256];
    char id[10];
    uart_write_blocking(uart1, "AT+CIPMUX=1\r\n", 13);
    if (getBlocks(buf, len, 10, "OK") < 0)
        return -1;
    uart_write_blocking(uart1, 
                       "AT+CIPSERVER=1,80\r\n", 19);
    if (getBlocks(buf, len, 10, "OK") < 0)
        return -1;
    for (;;)
    {
        if (getBlocks(buf, len, 1, "+IPD") < 0)
            continue;
        char *b = strstr(buf, "+IPD");
        b += 5;
        strncpy(temp, b, sizeof(temp));
        char *e = strstr(temp, ",");
        int d = e - temp;
        memset(id, '\0', sizeof(id));
        strncpy(id, temp, d);
        char data[] =  
           HTTP/1.0 200 OK\r\nServer: Pico\r\n
         Content-type: text/html\r\n\r\n
           <html><head><title>Temperature</title></head>
            <body><p>
             {\"humidity\":81%,\"airtemperature\":23.5C}
            </p></body>
           </html>\r\n";
        uint8_t command[128];
        int count = snprintf(command, 128,
            "AT+CIPSEND=%s,%d\r\n", id, strlen(data));
        uart_write_blocking(uart1, command, count);
        if (getBlocks(buf, len,  10, ">") < 0)
            return -1;

        uart_write_blocking(uart1, data, strlen(data));
        if (getBlocks(buf, len,  10, "OK") < 0)
            return -1;
        count = snprintf(command, 128, 
                          "AT+CIPCLOSE=%s\r\n", id);
        uart_write_blocking(uart1, command, count);
        if (getBlocks(buf, len, 10, "OK") < 0)
            return -1;
    }
    return 0;
}

int main()
{
    stdio_init_all();
    uint8_t buf[512];
    initWiFi();
    modeWiFi(buf, 512, 1);
    connectWiFi(buf, 512, "SSID", "password");
    getIPWiFi(buf, 512);
    startServerWiFi(buf, 512);
    sleep_ms(1000);
}

Summary

• Adding WiFi to the Pico is fairly easy using the low-cost ESP8266 ESP-01, which connects via the serial port and makes use of AT style commands to control the device as if it was a WiFi modem.

• In addition to an ESP8266, you also need a power supply capable of running it. The Pico seems able to do the job from its 3.3 output.

• You can use AT commands to set the device into client mode and connect to a WiFi network.

• While it is possible to use ad-hoc protocols, there are advantages in using TCP, HTTP and HTML so that other devices can work with the Pico.

• The Pico can use client mode to download data from web servers.

• It can also emulate a server to deliver data to any web browser or HTML-using client.

Related Articles

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Programming the Raspberry Pi Pico In C
Third Edition

By Harry Fairhead

Buy from Amazon.

Contents

• Preface
• Chapter 1 The Raspberry Pi Pico – Before We Begin
• Chapter 2 Getting Started
• Chapter 3 Using GPIO Lines
• Chapter 4 Some Electronics
     Extract: Erratum E9 Pull Down Problems ****NEW!
• Chapter 5 Simple Input
      Extract:   GPIO Input ***
• Chapter 6 Advanced Input – Events and Interrupts
• Chapter 7 Pulse Width Modulation
      Extract: Basic PWM ***
• Chapter 8 Controlling Motors And Servos
• Chapter 9 Getting Started With The SPI Bus
• Chapter 10 A-To-D and The SPI Bus
• Chapter 11 Using The I2C Bus
• Chapter 12 Using The PIO
      Extract: A 1-Wire PIO Program  ***
• Chapter 13 The DHT22 Sensor Implementing A Custom Protocol
• Chapter 14 The 1‑Wire Bus And The DS1820
• Chapter 15 The Serial Port
• Chapter 16 Using the Pico W
     Extract: Simple Web Client ***
     Extract:A Better Connect  ***
• Chapter 17 The Pico/W In C: Direct To Hardware *
• Chapter 18 Multicore and FreeRTOS

Extra: Adding WiFi To The Pico 2

*** Extracts from Edition 2 not yet updated.

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