Pyserial - Python creating byte array

Question

I have the following data

a1 = 0x5A -- hex

a2 = 0x01 -- hex

a3 = 12 -- decimal

a4 = 28 -- decimal

a5 = sum of (a1 to a4)

I should be able to send all this information in a byte array and send using ser.write command in one go.

Currently I am manually converting a3 and a4 to hex and I am using something like this ser.write('\x5A\x01\x...\x...\x...)

I would like a way, I could pack all the variables into a single byte array and say ser.write(bytearray)

ser --- is my serial.Serial('COM1')

Same with ser.read - the information I get is in byte array - How can I decode to decimals and hexdecimals

Looking for the use of binascii function for both converting to byte array and converting back from byte array

Laurent LAPORTE · Answer 1 · 2016-08-19T16:34:23.870

2

Do you want a string of hex values? Not sure to understand.

a1 = 0x5A # hex
a2 = 0x01 # hex
a3 = 12 # decimal
a4 = 28 # decimal
a5 = sum((a1, a2, a3, a4))

int_array = [a1, a2, a3, a4, a5]
print(int_array)

hex_array = "".join(map(hex, int_array))
print(hex_array)

You'll get:

[90, 1, 12, 28, 131]
0x5a0x10xc0x1c0x83

Using array class:

import array

byte_array = array.array('B', int_array)
print(byte_array)
print(byte_array.tostring())

You'll get:

array('B', [90, 1, 12, 28, 131])
b'Z\x01\x0c\x1c\x83'

edited Aug 19 '16 at 16:34

answered Aug 19 '16 at 16:17

Laurent LAPORTE

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Not a string of hex values but a BYTE ARRAY. That I could use to send a command using ser.write(bytearray) – Jesh Kundem Aug 19 '16 at 16:28
The ``sum`` get overflow a single byte size. Not always possible. – Laurent LAPORTE Aug 19 '16 at 16:30
0x5A should be one byte; 0x01 should be one byte, 12 should be one byte ... so on. I dont have to use the sum function – Jesh Kundem Aug 19 '16 at 16:31
I add an example using `array` class. – Laurent LAPORTE Aug 19 '16 at 16:35
It worked thank you Laurent. Could you also tell me how can I go back from a byte array to an int_array and a character array. Like ASCII values – Jesh Kundem Aug 19 '16 at 16:42
See: http://stackoverflow.com/questions/444591/convert-a-string-of-bytes-into-an-int-python – Laurent LAPORTE Aug 19 '16 at 16:43

Pyserial - Python creating byte array

1 Answers1