merge upstream

Author: AdamCummick

.readthedocs.yaml

@@ -9,7 +9,7 @@
 version: 2
 
 python:
-  version: "3.6"
+  version: "3.7"
   install:
     - requirements: docs/requirements.txt
     - requirements: requirements.txt

adafruit_wiznet5k/adafruit_wiznet5k.py

@@ -825,6 +825,10 @@ def socket_write(self, socket_num, buffer, timeout=0):
         ptr = (ptr + ret) & 0xFFFF
         self._write_sntx_wr(socket_num, ptr)
 
+        cntl_byte = 0x14 + (socket_num << 5)
+        txbuf = buffer[:ret]  # <- use ret
+        self.write(dst_addr, cntl_byte, txbuf)
+
         self._write_sncr(socket_num, CMD_SOCK_SEND)
         self._read_sncr(socket_num)