- Sun Jun 30, 2019 10:38 pm
#82959
Using hints from tutorials, I wrote a simple wifi server and client that only relay the characters received from the serial line (connected using USB to a PC) over the wifi to the other peer, and inc/dec a variable accordingly (see the code below). I used Arduino IDE (1.8.9) to write this code in a plain C/C++. The problem I am encountering is that this code works fine only after a power cycle (I have to unplug the USB cable from the module and plug it back again). If I only press the HW reset button on the module, or after I send a new version of the code (most of the times) everything works fine, except of the Serial.available() or Serial.read() functions. They simply see nothing arriving from the PC over USB/serial line. But replugging the USB and reconnecting the Putty terminal program (i.e. a full power cycle) resolves it, and everything works again. It always works properly after the power cycle, but most of the times fails after the RST button (or new version upload). Somehow the ESP serial module remains stuck or does not properly initialize when the module is reset without complete power loss. The same behavior on server and client. Replacing the module for a different one - same result. I used the most recent NodeMCU/ESP board settings downloaded yesterday using Arduino board manager. Do you, please, have any hints how to resolve this?
The code:
server:
client:
The code:
server:
Code: Select all
#include <ESP8266WiFi.h>
const char* ssid = "my ssid"; //replace this with your WiFi network name
const char* password = "my passwd"; //replace this with your WiFi network password
WiFiServer server(12345);
int a;
void setup()
{
a = 0;
pinMode(D5, OUTPUT); // piezo spkr
delay(1000);
Serial.begin(115200);
delay(1000);
tone(D5, 1720);
Serial.flush(); //irrelevant whether this is here or not
Serial.print("Wifi.begin()");
WiFi.begin(ssid, password);
Serial.println();
Serial.print("Connecting");
while (WiFi.status() != WL_CONNECTED)
{
delay(500);
Serial.print(".");
}
tone(D5, 220);
Serial.println("success!");
Serial.print("Server IP Address is: ");
Serial.println(WiFi.localIP());
delay(1000);
noTone(D5);
server.begin();
}
int read_and_process_packet(WiFiClient *client)
{
char packet_type = client->read();
switch (packet_type)
{
case 'a': a--; Serial.println(a); break;
case 'q': a++; Serial.println(a); break;
case '-': return 0;
}
return 1;
}
void loop() {
WiFiClient client = server.available();
if (client) {
if (client.connected()) {
Serial.println("Connected to client");
while (client.connected())
{
if (!read_and_process_packet(&client)) break;
if (Serial.available())
{
char c = Serial.read();
client.write(c);
}
delay(50);
}
client.stop();
Serial.println("Client left");
}
}
delay(1);
}client:
Code: Select all
#include <ESP8266WiFi.h>
// Replace these with your WiFi network settings
const char* ssid = "my ssid"; //replace this with your WiFi network name
const char* password = "my passwd"; //replace this with your WiFi network password
int a;
WiFiClient client;
char server_ip[20];
void setup()
{
a = 0;
pinMode(D5, OUTPUT);
delay(1000);
Serial.begin(115200);
delay(1000);
Serial.flush(); //irrelevant whether this is here or not
Serial.print("Enter server IP: ");
char *p = server_ip;
for (int i = 0; i < 4; i++)
{
int ip = read_number();
p = print_num(p, ip);
if (i < 3)
p = print_char(p, '.');
}
Serial.println();
tone(D5, 1720);
Serial.print("Wifi.begin()");
