B&K Precision 866C Manual de usuario descargar pdf (Pagina 47)

print " ",

s = "%02x" % ord(bytes[i])

if s == "00":

s = chr(250)*2

print s,

def CalculateChecksum(cmd):

assert((len(cmd) == length_packet - 1) or (len(cmd) ==

length_packet))

checksum = 0

for i in xrange(length_packet - 1):

checksum += ord(cmd[i])

checksum %= 256

return checksum

def main():

port = 3 # COM4 for my computer

baudrate = 38400

sp = serial.Serial(port, baudrate) # Open a serial connection

# Construct a set to remote command

cmd = chr(0xaa) + chr(0x00) + chr(0x20) # First three bytes

cmd += chr(0x01) + chr(0x00)*(length_packet - 1 - 4)

cmd += chr(CalculateChecksum(cmd))

assert(len(cmd) == length_packet)

# Send command to DC load

sp.write(cmd)

print "Set to remote command:"

DumpCommand(cmd)

# Get response from DC load

response = sp.read(length_packet)

assert(len(response) == length_packet)

print "Response:"

DumpCommand(response)

main()

The first three lines of the ma i n ( ) function set up a serial port to talk to. The next five lines construct

the string that we will send to the DC load. The c h r ( ) function creates a single character that has

the ASCII value of the argument. The + symbols allow strings to be concatenated. The expression

c h r ( 0 ) * a _ n u m b e r creates a string of ASCII 0x 0 0 characters whose length is a _ n u m b e r . . The last

character is the checksum of the previous 25 characters, calculated for us by the

Ca l c u l a t e C h e c k s u m ( ) function.

When a command is sent to the instrument, you must always request for return data, which will

always be another 26 bytes. This is also dumped to the screen.

You can download a complete python program along with detailed documentation from our website

at www.bkprecision.com

8500 DC Load Series Version: November 4, 2008 Page 47 of 76

1 2 ... 42 43 44 45 46 47 48 49 50 51 52 ... 75 76

Comentarios a estos manuales

Sin comentarios

B&K Precision 866C Manual de usuario Pagina 47

Comentarios a estos manuales

Relacionado con productos y manuales para De medición, control y control B&K Precision 866C