Change PySerial or other module similar

[davidvaran...@gmail.com]

Hi,

I would like to know if exist any other module to communicate via serial in python, instead of PySerial.

I want to know this because, PySerial only communicate with "string", and i have a microcontroller that will receive data from a BeagleBone Black, and i shouldnt do an algoritm on this microcontroller to change strings to int or bytes, because will spend a lot of processing, and every character on a string uses one byte, and that will occupate a lot on this micro.

Saying this, i want to send data in int/hex or binary format instead of string from the BeagleBone side, other solution can be change the PySerial module to do this.

Any help will be aprecciated.

Best Regards,

David

[Mark Barton]

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Hi David,
PySerial is the way to go. Python has several ways to do the conversion for you. Google around a bit and you will find several examples.

Use the array module if you want to send several bytes using PySerial. Here is an example of sending a list of data. msgList is a list of integer data to send. For example msgList = [1,2,3,4,5] and serialObj is the opened serial stream.

        import array

        binMessage = array.array('B') <-- creates an empty binary array
        binMessage.extend(msgList) <-- converts and copies the list to the array
        serialObj.write(binMessage.tostring()) <-- Send it out. Notice the tostring function
        serialObj.flush()

Mark

[Dennis Lee Bieber]

On Thu, 9 Mar 2017 04:34:43 -0800 (PST),
davidvaran...@gmail.com declaimed the
following:

>
>I want to know this because, PySerial only communicate with "string", and i

It sends bytes (at least, in Python 2.x -- not sure if Python 3.x uses
unicode or byte as the native component for PySerial), packaged in a Python
string data type.

There is no constraint on what those bytes contain, beyond that imposed
by the console (console output -- print theString -- may try to convert
non-ASCII values to something unusable).

>
>Saying this, i want to send data in int/hex or binary format instead of
>string from the BeagleBone side, other solution can be change the PySerial
>module to do this.
>

"hex" is, to most people, a character string representation of a binary
value using a radix of 16 -- which means each byte of the raw data is
represented by two characters, one for each four bits.

>Any help will be aprecciated.

Read the library reference manual section describing the struct module.


>>> import struct
>>> it = 202
>>> bt = "6"
>>> ft = 3.14159
>>> pck = struct.pack("!hiqBBifd",
... it, it, it, it, ord(bt), ord(bt), ft, ft)
>>>
>>> repr(pck)
"'\\x00\\xca\\x00\\x00\\x00\\xca\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\xca\\xca6\\x00\\x00\\x006@I\\x0f\\xd0@\\t!\\xf9\\xf0\\x1b\\x86n'"
>>>


The format string is (repr() shows each byte, and if printable, does
not show the xNN format):

! network byte order
h (signed) short 202 => x00ca
i (signed) integer 202 => x000000ca
q (signed) long-long 202 => x00000000000000ca
B unsigned char (integer data type -- "c" is 1-character string) 202 =>
xca
B unsigned char (need ord() to get integer) ord("6") => 54 => '6'
i (signed) integer ord("6") => 54 => x00 and '6'
f float 3.14159 => '@I' and x04d0
d double 3.14159 =>
'@' and <tab> and '!' and xf9f01b86 and 'n'


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wlf...@ix.netcom.com HTTP://wlfraed.home.netcom.com/

[David Caniceiro]

Thanks for your answers guys,

testing the Dennis answer, and after read the struct information,i reached a solution:

if i use -> struct.pack('B',255)

now only use one byte on serial communication, instead of 3 bytes like i was doing before(sending a string '255')

But after some tests, i confirmed if i use the hex string directly on write. its works too.

 Ex::  serial.write('\xFF')

Thanks again for the answers, and sorry for being newbie.

Best Regards,

David 

2017-03-09 14:57 GMT+00:00 Dennis Lee Bieber <wlf...@ix.netcom.com>:

On Thu, 9 Mar 2017 04:34:43 -0800 (PST),

davidvarandacaniceiro@gmail.com declaimed the

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[daniel.di...@gmail.com]

If you just have to send bytes, you can find useful to use a bytearray.
[Python 3]
serial.write(bytearray([255]))
serial.write(bytearray([2, 75, 250]))

The struct module is still useful to send C style values, but I suggest you make explicit whether you are using little or big-endian to avoid confusion (default will use otherwise the machine running the code default which may change when you move the code to other machine):
struct.pack('>L', 75655)

El dijous, 9 març de 2017 19:09:12 UTC+1, David Caniceiro va escriure:

Thanks for your answers guys,

testing the Dennis answer, and after read the struct information,i reached a solution:

if i use -> struct.pack('B',255)

now only use one byte on serial communication, instead of 3 bytes like i was doing before(sending a string '255')

But after some tests, i confirmed if i use the hex string directly on write. its works too.

 Ex::  serial.write('\xFF')

Thanks again for the answers, and sorry for being newbie.

Best Regards,

David 

2017-03-09 14:57 GMT+00:00 Dennis Lee Bieber <wlf...@ix.netcom.com>:

On Thu, 9 Mar 2017 04:34:43 -0800 (PST),

davidvaran...@gmail.com declaimed the

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