Switch await core.sleep to await core.io_queue.queue_[read|write]

asyncio/stream.py

@@ -61,7 +61,7 @@ async def read(self, n):
         """
 
         core._io_queue.queue_read(self.s)
-        await core.sleep(0)
+        yield
         return self.s.read(n)
 
     async def readinto(self, buf):
@@ -73,7 +73,7 @@ async def readinto(self, buf):
         """
 
         core._io_queue.queue_read(self.s)
-        await core.sleep(0)
+        yield
         return self.s.readinto(buf)
 
     async def readexactly(self, n):
@@ -88,7 +88,7 @@ async def readexactly(self, n):
         r = b""
         while n:
             core._io_queue.queue_read(self.s)
-            await core.sleep(0)
+            yield
             r2 = self.s.read(n)
             if r2 is not None:
                 if not len(r2):
@@ -106,7 +106,7 @@ async def readline(self):
         l = b""
         while True:
             core._io_queue.queue_read(self.s)
-            await core.sleep(0)
+            yield
             l2 = self.s.readline()  # may do multiple reads but won't block
             l += l2
             if not l2 or l[-1] == 10:  # \n (check l in case l2 is str)
@@ -129,7 +129,8 @@ async def drain(self):
         mv = memoryview(self.out_buf)
         off = 0
         while off < len(mv):
-            yield core._io_queue.queue_write(self.s)
+            core._io_queue.queue_write(self.s)
+            yield
             ret = self.s.write(mv[off:])
             if ret is not None:
                 off += ret

examples/usb_cdc_boot.py

@@ -0,0 +1,2 @@
+import usb_cdc
+usb_cdc.enable(data=True, console=True)

examples/usb_cdc_example.py

@@ -0,0 +1,34 @@
+"""
+example that reads from the cdc data serial port in groups of four and prints
+to the console. The USB CDC data serial port will need enabling. This can be done
+by copying examples/usb_cdc_boot.py to boot.py in the CIRCUITPY directory
+
+Meanwhile a simple counter counts up every second and also prints
+to the console.
+"""
+
+
+import asyncio
+import usb_cdc
+
+async def client():
+    usb_cdc.data.timeout=0
+    s = asyncio.StreamReader(usb_cdc.data)
+    while True:
+        text = await s.readline()
+        print(text)
+        await asyncio.sleep(0)
+
+async def counter():
+    i = 0
+    while True:
+        print(i)
+        i += 1
+        await asyncio.sleep(1)
+
+async def main():
+    client_task = asyncio.create_task(client())
+    count_task = asyncio.create_task(counter())
+    await asyncio.gather(client_task, count_task)
+
+asyncio.run(main())