'NoneType' has no len() - When reading from UART - Serial Bridge MAX3232

[JohannesNeu]

Hi everyone,

I have connected the serial console of my homeserver to a MAX3232 Converter and attached said converter to my ESP32 via UART. With Microdot I provide a website to watch the boot messages using xterm.js and a websocket:

I had help over here .

As you can see from the image, the UART output is pretty garbled, I am reading it with readline and convert it to a string :

uart = UART(2, 115200)
@app.route('/echo')
@with_websocket
async def echo(request, ws):
while True:
if uart.readline() is not None:
await ws.send (str(uart.readline()))

I tried with read(), but Nones still seem to slip through, because with:

uart = UART(2, 115200)
@app.route('/echo')
@with_websocket
async def echo(request, ws):
while True:
if uart.read() is not None:
await ws.send (uart.read())

I am getting aTypeError: object of type 'NoneType' has no len() error.

I would appreciate any ideas and insights on how to best forward the UART information to the websocket or how to filter out the NoneTypes.

[JohannesNeu]

Ok, I think I figured it out. The while True would send Nones to the websocket even with the filter within if there was no new information.

This fixed it:

def passthrough(inputstream):
if inputstream is None:
return ""
else:
return inputstream

@app.route('/echo')
@with_websocket
async def echo(request, ws):
while True:
await ws.send(passthrough(uart.read()))

The output looks actually very nice now: