improve robustness of kat500 serial commands

src/kpa500-remote/kat500.py

@@ -335,7 +335,7 @@ async def kat500_server(self):
                         next_command += 1
 
                 # timeout = 2.0 if query in (b'MDA;', b'MDB;', b'MDM;') else 0.05
-                await self.device_send_receive(query, bl)
+                await self.device_send_receive(query, bl, retries=2)
                 if query == b'PS0;':
                     tuner_state = 1
                     logging.info('power off command, tuner state 3-->1', 'kat500:kat500_server')

src/kpa500-remote/kdevice.py

@@ -89,16 +89,25 @@ def update_device_data(self, index, value):
                 if index not in network_client.update_list:
                     network_client.update_list.append(index)
 
-    async def device_send_receive(self, message, buf_and_length, wait_time=0.10):
-        # should the read buffer be flushed? can only read to drain
-        device_port = self.device_port
-        # empty the receive buffer
-        while device_port.readinto(buf_and_length.buffer) > 0:
-            logging.warning(f'waiting to send "{message}", rx buffer was not empty: "{buf_and_length.buffer}"')
-        device_port.write(message)
-        device_port.flush()
-        await asyncio.sleep(wait_time)
-        buf_and_length.bytes_received = device_port.readinto(buf_and_length.buffer)
+    async def device_send_receive(self, message, buf_and_length, wait_time=0.50, retries=1):
+        while retries > 0:
+            retries -= 1
+            device_port = self.device_port
+            # empty the receive buffer
+            while device_port.readinto(buf_and_length.buffer) > 0:
+                logging.warning(f'waiting to send "{message}", rx buffer was not empty: "{buf_and_length.buffer}"')
+            device_port.write(message)
+            device_port.flush()
+            while wait_time > 0:
+                await asyncio.sleep(0.01)
+                wait_time -= 0.01
+                if device_port.any() > 0:
+                    break
+            buf_and_length.bytes_received = device_port.readinto(buf_and_length.buffer)
+            if buf_and_length.bytes_received > 0:
+                return
+            if retries > 0:
+                logging.debug(f'received {buf_and_length.bytes_received} bytes response to {message}, retrying')
 
     @staticmethod
     async def read_network_client(reader):

src/kpa500-remote/serialport.py

@@ -32,10 +32,11 @@
 import sys
 
 impl_name = sys.implementation.name
-if impl_name == 'cpython':
-    import serial
-elif impl_name == 'micropython':
+upython = impl_name == 'micropython'
+if upython:
     import machine
+else:
+    import serial
 
 
 class SerialPort:
@@ -75,6 +76,19 @@ def __init__(self, name='', baudrate=19200, timeout=0.040):
     def close(self):
         self.port.close()
 
+    def any(self):
+        if upython:
+            return self.port.any()
+        else:
+            return self.port.in_waiting()
+
+    def flush_input(self):
+        if upython:
+            if self.any():
+                _ = self.port.read()
+        else:
+            self.port.reset_input_buffer()
+
     def write(self, buffer):
         self.port.write(buffer)