Hi!
Thanks for your reply. Yes, the Board is crappy designed but I just got 4 of them for free, so I wanted to give it a try

I managed to get it to work.
There is an Attiny2313 on the board to set the Relais. I already tried to flash the Attiny but it doesnt really work out, so I flashed it back.
The reason why it didnt work to use the RX/TX Output directly on the boards connection is the MAX232 Chip. I soldered my wires directly to the Attiny 2313 and it worked!
Here is my function I used (using Myserial)
void sendCommand(int command, int cardAddr, int data){
byte bytes[4];
bytes[0] = byte(command);
bytes[1] = byte(cardAddr);
bytes[2] = byte(data);
bytes[3] = bytes[0] ^ bytes[1] ^ bytes[2];
writeBytes(bytes,4);
delay(250);
}
void writeBytes(byte arr[], int len){
for(int i = 0; i < len; i++){
mySerial.write(arr[i]);
}
}
First you have to Initialise them (1.0.0) then Set them (3.0.x). Works good.
The next step is Adding the Webserver capability. I already tested it using the simpled Webserver youll find when googling "ArduinoWebServerLED".
I wanted to use the SDcard to store my Website, but how can I do that? I already found "TinyWebServer" but even the examples it wont compile

SimpleWebServer.ino:11:19: warning: Flash.h: No such file or directory
SimpleWebServer.ino: In function 'boolean index_handler(TinyWebServer&)':
SimpleWebServer.ino:38: warning: only initialized variables can be placed into program memory area
SimpleWebServer:38: error: no match for 'operator<<' in 'web_server << (const __FlashStringHelper*)({...})'
SimpleWebServer.ino: In function 'const char* ip_to_str(const uint8_t*)':
SimpleWebServer.ino:48: warning: embedded '\0' in format
SimpleWebServer.ino: In function 'void setup()':
SimpleWebServer.ino:54: warning: only initialized variables can be placed into program memory area
SimpleWebServer:54: error: expected `)' before 'FreeRam'
SimpleWebServer:54: error: expected `)' before ';' token
SimpleWebServer.ino:72: warning: only initialized variables can be placed into program memory area
SimpleWebServer:72: error: no match for 'operator<<' in 'Serial << (const __FlashStringHelper*)({...})'
SimpleWebServer.ino:76: warning: only initialized variables can be placed into program memory area
SimpleWebServer:76: error: no match for 'operator<<' in 'Serial << (const __FlashStringHelper*)({...})'
SimpleWebServer.ino:79: warning: only initialized variables can be placed into program memory area
SimpleWebServer:79: error: no match for 'operator<<' in 'Serial << (const __FlashStringHelper*)({...})'
Are there any Libraries I can use? Is there "ONE" library everyone uses for those Webservers (using SD-Card for switching pins or sth.)?