Radio Shack WX200 Weather station emulator

Y

yv1hx

Member
Hello folks,

I'm trying to develop a emulator based in the Radio Shack WX200 Weather station protocol http://wx200.planetfall.com/wx200.txt, to but I cannot guess how to do the Unsigned sum of first xx bytes as stated in the specs.

Below is one of my failed attempts (with a fixed string):

Code: 
#picaxe 28x2
#com 3
#terminal 9600
setfreq m8
;***** Symbol definitions *****
symbol SerialOut	= a.4	; Serial port
symbol Led 		= a.0 ' Running led
Symbol StartPacket = 0xFF	' Start Packet delimiter
Symbol lsd = b10
Symbol msd = b11
Symbol Checksum = b12

symbol FirstDigit = b7
symbol SecondDigit = b8

high Led	'turns on LED
pause 5000	' Pause 4 seconds 
low SerialOut
pause 50
'

do
low led
gosub SentTestPacket
pause 5000	' Prints hold-on message .
high led
pause 50
loop


SentTestPacket:
Checksum = 0x00
Checksum = Checksum | StartPacket
Checksum = Checksum | 0x02
Checksum = Checksum | 0x81
Checksum = Checksum | 0x71
Checksum = Checksum | 0x00
Checksum = Checksum | 0x87
Checksum = Checksum | 0x05
'Checksum = Checksum | 0xff
'Checksum = Checksum | 0x0c
'Checksum = Checksum | 0x50
'Checksum = Checksum | 0x79

msd = Checksum / 16 + "0" : if msd > "9" then : msd = msd + 7 : end if
lsd = Checksum & $F + "0" : if lsd > "9" then : lsd = lsd + 7 : end if

SerOut SerialOut, N9600, (StartPacket,0x02, 0x81, 0x71, 0x00, 0x87, 0x05, 0xff)
pause 50
return
I forgot to mention, this project is to be used as "protocol translator" between a Vaisala WXT520 Weather transmitter and the prestigious software http://sandaysoft.com/products/cumulus

Thanks in advance :D
 
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