CODEWITHSUNDEEP
python
SYM2020
SYM2020

Reputation: 23

Read a binary file and send over Modbus RTU using Python 3 (how to convert 'str' to an 'int')

I have made a PCB circuit that has a microcontroller (Microchip PIC18F47K40) that can program a parallel flash memory (Microchip SST39SF040).

The microcontroller communicates to my PC (Windows 10) via Modbus RTU over a USB to UART adaptor.

I use five Modbus registers...

Control, Address0, Address1, Address2, Data

Control = read, write, erase

Address0,1,2 = Address bus

Data = Data bus

Using Baseblock program I have verified the microcontroller is working fine, and in Python I can send individual commands ok.

My goal is to be able to read in a binary file and send to the microcontroller to program the flash memory chip.

This is the code I have so far: -

#!/usr/bin/env python3

import minimalmodbus
instrument = minimalmodbus.Instrument('COM8', 1)
instrument.serial.baudrate = 9600
instrument.close_port_after_each_call = True

addressCount = 0
with open("rom.bin", "rb") as f:
    while (dataByte := f.read(1)):
        addressBytes = ( (addressCount).to_bytes(3, byteorder='little') )
        addressCount += 1
        instrument.write_register(0, 0x3, 0)
        instrument.write_register(1, addressBytes[0], 0)
        instrument.write_register(2, addressBytes[1], 0)
        instrument.write_register(3, addressBytes[2], 0)
        #instrument.write_register(4, dataByte.hex(), 0)
        print(dataByte.hex())

The line that is causing me problems is: -

instrument.write_register(4, dataByte.hex(), 0)

The error message: -

Exception has occurred: TypeError
The input value must be numerical. Given: '85'
  File "X:\Code\Python\1-modbus_master_flas_read_write_erase\#4 - numpy.py", line 17, in <module>
    instrument.write_register(4, dataByte.hex(), 0)

When I check the type for dataByte.hex() it comes back as a str...

So, my question, how do I convert the str to an int?

Upvotes: 1

Views: 755

Answers (1)

Nico M&#252;ller
Nico M&#252;ller

Reputation: 1874

You can use int(dataByte.hex())

databyte = b'101010'
databyte = databyte.hex()
print(type(databyte)) # <class 'str'>
databyte = int(databyte,16)
print(type(databyte)) # <class 'int'>

Upvotes: 1

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