I try to display the transmitted information from CAN bus on ESP32 web server. I saved the CAN.read() in a buffer receivedChars[i] and try to display the data by client.println(receivedChars[i]);}. However, nothing shows on the webserver... The complete code shows below,
// Copyright (c) Sandeep Mistry. All rights reserved.
// Licensed under the MIT license. See LICENSE file in the project root for full license information.
#include <CAN.h>
#include <Wire.h>
#include <Adafruit_GFX.h>
#include <Adafruit_SSD1306.h>
#include <WiFi.h>
#define SCREEN_WIDTH 128 // OLED display width, in pixels
#define SCREEN_HEIGHT 32 // OLED display height, in pixels
// Replace with your network credentials
const char* ssid = "NGW_2.4G";
const char* password = "NextGW2018";
// Set webserver port number to 80
WiFiServer server(80);
// Variable to store the HTTP request
String header;
// Declaration for an SSD1306 display connected to I2C (SDA, SCL pins)
Adafruit_SSD1306 display(SCREEN_WIDTH, SCREEN_HEIGHT, &Wire, -1);
void setup() {
Serial.begin(115200);
while (!Serial);
if (!display.begin(SSD1306_SWITCHCAPVCC, 0x3C)) {
Serial.println(F("SSD1306 allocation failed"));
for (;;);
}
delay(2000);
display.clearDisplay();
display.setTextColor(WHITE);
Serial.println("CAN Receiver");
CAN.setPins(16, 17);
// start the CAN bus at 500 kbps
if (!CAN.begin(500E3)) {
Serial.println("Starting CAN failed!");
while (1);
}
// Connect to Wi-Fi network with SSID and password
Serial.print("Connecting to ");
Serial.println(ssid);
WiFi.begin(ssid, password);
while (WiFi.status() != WL_CONNECTED) {
delay(500);
Serial.print(".");
}
// Print local IP address and start web server
Serial.println("");
Serial.println("WiFi connected.");
Serial.println("IP address: ");
Serial.println(WiFi.localIP());
server.begin();
}
void loop() {
char receivedChars[10];
// try to parse packet
int packetSize = CAN.parsePacket();
if (packetSize) {
// received a packet
Serial.print("Received ");
if (CAN.packetExtended()) {
Serial.print("extended ");
}
if (CAN.packetRtr()) {
// Remote transmission request, packet contains no data
Serial.print("RTR ");
}
Serial.print("packet with id 0x");
Serial.print(CAN.packetId(), HEX);
if (CAN.packetRtr())
{
Serial.print(" and requested length ");
Serial.println(CAN.packetDlc());
}
else
{
Serial.print(" and length ");
Serial.println(packetSize);
// only print packet data for non-RTR packets
while (CAN.available())
{
for (int i=0; i<5; i++)
{
receivedChars[i] = (char)CAN.read();
Serial.print(receivedChars[i]);
}
}
Serial.println();
}
Serial.println();
}
WiFiClient client = server.available(); // Listen for incoming clients
if (client) { // If a new client connects,
Serial.println("New Client."); // print a message out in the serial port
String currentLine = ""; // make a String to hold incoming data from the client
while (client.connected()) { // loop while the client's connected
if (client.available()) { // if there's bytes to read from the client,
char c = client.read(); // read a byte, then
Serial.write(c); // print it out the serial monitor
header += c;
if (c == '\n') { // if the byte is a newline character
// if the current line is blank, you got two newline characters in a row.
// that's the end of the client HTTP request, so send a response:
if (currentLine.length() == 0) {
// HTTP headers always start with a response code (e.g. HTTP/1.1 200 OK)
// and a content-type so the client knows what's coming, then a blank line:
client.println("HTTP/1.1 200 OK");
client.println("Content-type:text/html");
client.println("Connection: close");
client.println();
// Display the HTML web page
client.println("<!DOCTYPE html><html>");
client.println("<head><meta name=\"viewport\" content=\"width=device-width, initial-scale=1\">");
client.println("<link rel=\"icon\" href=\"data:,\">");
// CSS to style the table
client.println("<style>body { text-align: center; font-family: \"Trebuchet MS\", Arial;}");
client.println("table { border-collapse: collapse; width:35%; margin-left:auto; margin-right:auto; }");
client.println("th { padding: 12px; background-color: #0043af; color: white; }");
client.println("tr { border: 1px solid #ddd; padding: 12px; }");
client.println("tr:hover { background-color: #bcbcbc; }");
client.println("td { border: none; padding: 12px; }");
client.println(".sensor { color:white; font-weight: bold; background-color: #bcbcbc; padding: 1px; }");
// Web Page Heading
client.println("</style></head><body><h1>Can bus</h1>");
client.println("<tr><td>text: </td><td><span class=\"sensor\">");
for (int i=0; i<5; i++)
{
receivedChars[i] = (char)CAN.read();
client.println(receivedChars[i]);
}
client.println(" .</span></td></tr>");
// The HTTP response ends with another blank line
client.println();
// Break out of the while loop
break;
} else { // if you got a newline, then clear currentLine
currentLine = "";
}
} else if (c != '\r') { // if you got anything else but a carriage return character,
currentLine += c; // add it to the end of the currentLine
}
}
}
// Clear the header variable
header = "";
// Close the connection
client.stop();
Serial.println("Client disconnected.");
Serial.println("");
}
}
1 Answer 1
It looks like the CAN-BUS can not be activated in web server session, I save the transmitted information in a buffer before starting the web server session, and print out the information from the buffer.
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