W5200 UDP not working??? Teensy 3.2

[olivierdemoustier]

I'm used to work with W5100 ethernet shields. Never had problems. But need to go faster now. So I bought wiz820io. based on W5200 chipset. Whatever I do I cannot receive UDP packets. I have tried multiple Ethernet Libraries. including https://github.com/PaulStoffregen/Ethernet.
I Have communication with the shield because it pings me the Ip adress and tels me it is a W5200. (see code). But no packets are received. If I use the same code on a W5100. It works perfectly. What am I doing wrong? Please advice.

//PINOUT: WIZ820io :SCK=13 MISO=12 MOSI=11 CS=10 RST=9 PWDN=gnd

#include <SPI.h>
#include <Ethernet.h>
#include <EthernetUdp.h>


byte Mac[] = {0x74,0x69,0x69,0x2D,0x30,0x15};
IPAddress ip(192, 168, 1, 179);

EthernetUDP Udp;


void setup() {
//reset the WIZ820io
pinMode(9, OUTPUT);
digitalWrite(9, LOW); // begin reset the WIZ820io
delay(50);
digitalWrite(9, HIGH); // end reset pulse
delay(5000);

Serial.begin(19200);
delay(10); // let UART settle

Ethernet.begin(Mac, ip );

// Check for Ethernet hardware present
if (Ethernet.hardwareStatus() == EthernetNoHardware) {
Serial.println("Ethernet shield was not found. Sorry, can't run without hardware. ");
while (true) {
delay(1); // do nothing, no point running without Ethernet hardware
}
}
if (Ethernet.hardwareStatus() == EthernetW5200) {
Serial.println("W5200");
}
if (Ethernet.hardwareStatus() == EthernetW5100) {
Serial.println("W5100");
}
if (Ethernet.hardwareStatus() == EthernetW5500) {
Serial.println("W5500");
}
// Check for Ethernet cable connected
if (Ethernet.linkStatus() == LinkOFF) {
Serial.println("Ethernet cable is not connected.");
}

Udp.begin(5568);

delay(10);
// Check if IP adress is set to WIZ820io
Serial.print("ip adress : ");
Serial.println(Ethernet.localIP());
delay(1000);
}



void loop() {

//Process packets
int packetSize = Udp.parsePacket(); //Read UDP packet count

if (packetSize) {
Serial.print("Packet received with size = ");
Serial.println(packetSize);
// Udp.read(gPacketBuffer, ETHERNET_BUFFER); //read UDP packet
}
}