call yield() if client.write() is waiting for free memory block

Author: JAndrassy

README.md

@@ -8,6 +8,7 @@ The modernization includes:
 * SPI transactions to share the SPI bus with devices with different communication settings
 * SPI communication at 20 MHz if the MCU supports it, else on the maximum supported by the MCU
 * client.flush() to send the packet immediately
+* calls yield() in blocking functions 
 
 [The documentation of Arduino Ethernet library](https://www.arduino.cc/en/Reference/Ethernet) applies for classes and functions descriptions.
 

src/Ethernet.cpp

@@ -330,6 +330,20 @@ void UIPEthernetClass::configure(IPAddress ip, IPAddress dns, IPAddress gateway,
   _dnsServerAddress = dns;
 }
 
+void
+UIPEthernetClass::call_yield()
+{
+  static bool in_yield;
+  static uint32_t last_call_millis;
+  if (!in_yield && millis() - last_call_millis > 0)
+    {
+      last_call_millis = millis();
+      in_yield = true;
+      yield();
+      in_yield = false;
+    }
+}
+
 /*---------------------------------------------------------------------------*/
 uint16_t
 UIPEthernetClass::chksum(uint16_t sum, const uint8_t *data, uint16_t len)

src/Ethernet.h

@@ -117,6 +117,8 @@ class UIPEthernetClass
 
   static boolean network_send();
 
+  static void call_yield();
+
   friend class EthernetServer;
 
   friend class EthernetClient;

src/EthernetClient.cpp

@@ -184,6 +184,7 @@ UIPClient::write(const uint8_t *buf, size_t size)
                   goto ready;
                 }
 #endif
+              Ethernet.call_yield();
               goto repeat;
             }
           u->out_pos = 0;
@@ -217,6 +218,7 @@ UIPClient::write(const uint8_t *buf, size_t size)
                   goto ready;
                 }
 #endif
+              Ethernet.call_yield();
               goto repeat;
             }
           p++;