UART write human-readable ASCII text

[gatorchu]

First of all, I noticed that the UART class in both MicroPython and Pycom shared same syntax, so I post my question in this category. hopefully, I don't break the rule.

I'm working on Lopy4 interfacing with Nextion serial display (http://nextion.tech/instruction-set/#s6).

To send the data to the monitor for displaying, I must follow their rules (see below Arduino code for instance).

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//Serial print ASCII text "voltage1.val=" to the display serial port
Serial.print("voltage1.val=");     
//Then Print the value we want to be displayed to the display serial port     
Serial.print(Value);                        
//Always terminated with 3 full bytes after... 
Serial.write(0xff);                               
Serial.write(0xff);
Serial.write(0xff);

Sample code from https://www.electronoobs.com/eng_arduino_tut60_1.php

I had tried to migrate the Arduino code to Lopy4, but never make it works. After investigating, my understanding is that

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uart.write()

can not accomplish the work that

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Serial.print()

in Arduino does. Because the former write a series of bytes to the serial port, while the latter one prints human-readable ASCII text to the serial port.

So my question is can UART port write human-readable ASCII text? Please give some instructions. Thank you!

[dhylands]

Sure.

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uart.write('This is a test\r\n')

is perfectly valid code in MicroPython.

And if I jumper the Tx and Rx signals together, then I can read it back too:

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>>> u = pyb.UART(6,115200)
>>> u.write('This is a test\r\n')
16
>>> r = u.read()
>>> print(r)
b'This is a test\r\n'
>>> r.decode()
'This is a test\r\n'
>>> 

Note that when reading you'll get back bytes. You can convert that to a regular string by calling decode()

It's important to understand the difference between string objects like 'Test' and bytes b'Test'

string objects are UTF-8 encoded, whereas bytes are just a collection of bytes and may include sequences which are not valid UTF-8.

The Arduino doesn't understand UTF8 and everything there is really bytes.

[Roberthh]

Python does not automagically convert non-string items to strings, like the Serial class of Arduino does. You can use the str() function of Python to get a strings representation of non-string objects. Of you use the formatting operators % or the format method of strings.

[dhylands]

Sorry I missed the point of that post. It turns out that you can use a UART as a file device with print as well.

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>>> u = pyb.UART(6, 115200)
>>> x = 42
>>> y = 'foo'
>>> z = {'a':32}
>>> print('x =', x, 'y =', y, 'z =', z, file=u)
>>> u.read()
b"x = 42 y = foo z = {'a': 32}\n"
>>> 

The above was done on my Pyboard 1.0 with Y1 jumpered to Y2.

[gatorchu]

Thank you, dhylands and Roberthh!
I got it works right now! Your explanation helps a lot!