pybk8500 0.2.0

BK-8500-Electronic-Load python library

Python library for the BK Precision 8500 SERIES DC ELECTRONIC LOADS

Models 8500, 8502, 8510, 8512, 8514, 8518, 8520, 8522, 8524 & 8526

Protocol found at https://bkpmedia.s3.amazonaws.com/downloads/manuals/en-us/85xx_manual.pdf in the “Command details” section.

Command Line Interface

I added some command line interface utilities that use python’s “-m” module switch.

Requirements

• pyserial>=3.4

• continuous-threading>=2.0.0

Send Command

Send a command to a serial port and wait for a response.

python -m pybk8500.send_cmd "COM1" 9600 "Command Status" --address 1
# will send the command down a serial port and wait for a response

The command ID can be the string NAME or integer ID.

# cmd_id as str
python -m pybk8500.send_cmd "COM1" 9600 "Command Status" --address 1

# cmd_id as hex
python -m pybk8500.send_cmd "COM1" 9600 0x12 --address 1

# cmd_id as decimal
python -m pybk8500.send_cmd "COM1" 9600 18 --address 1

Parser

The parser is used to parse incoming messages. It can be used with to parse single messages, parse messages with an iterator, or parse using a callback function.

Parse Iterator Example

Use a for loop to iterate through parsed messages.

import pybk8500

with open('saved_messages.txt', 'rb') as f:
    p = pybk8500.Parser()

    for msg in p.parse_iter(f.read()):
        print(msg.NAME)
        for field, value in msg.fields().items():
            print('\t{} = {}'.format(field, value))

Parse Callback Example

Use a callback function to handle parsed messages. This is useful for GUI’s with a serial port.

import sys
import pybk8500

def print_error(error):
    print('{}: {}'.format(type(error).__name__, str(error)), file=sys.stderr)

def print_msg(msg):
    print(msg.NAME)
    for field, value in msg.fields().items():
        print('\t{} = {}'.format(field, value))

p = pybk8500.Parser()
p.error = print_error

with open('saved_messages.txt', 'rb') as f:
    p.parse(f.read(), print_msg)

Parse Single Message Example

Parse a single message at a time.

import sys
import pybk8500

def print_error(error):
    print('{}: {}'.format(type(error).__name__, str(error)), file=sys.stderr)


with open('saved_messages.txt', 'rb') as f:
    p = pybk8500.Parser()

    byts = f.read()
    while True:
        msg, error, byts = self.parse_msg(byts)
        if msg is not None:
            print(msg.NAME)
            for field, value in msg.fields().items():
                print('\t{} = {}'.format(field, value))
        elif error is not None:
            print_error(error)
        else:
            break

Commands

Generate commands and send them down a serial port

Requirements

• pyserial

pip install pyserial

Use Commands

Create and use command easily.

Commands can be found at https://bkpmedia.s3.amazonaws.com/downloads/manuals/en-us/85xx_manual.pdf in the “Command details” section.

import pybk8500
import serial

ser = serial.Serial('COM1', 9600)

cmd = pybk8500.SetRemoteOperation(address=1, operation='Remote')
ser.write(bytes(cmd))

# Most commands have a value alias
cmd = pybk8500.SetRemoteOperation(address=1, value='Remote')
ser.write(bytes(cmd))

Commands are bytearrays which can be used as bytes. When you change a value a flag is set to indicate that the checksum must be recalculated. Calling bytes(cmd) will recalculate the checksum before converting to bytes.