How to calculate Serial Command Checksums for HP-1

Status
Not open for further replies.

dfw1417

Member
Joined
Dec 19, 2002
Messages
71
Location
DFW Texas
Looking for an example of Checksum Calculation for sending commands to HP-1 via the serial port.

Prior the the HP-1 Checksums were not required for serial port commands sent.

Example:

I want to send this command (from the protocol doc) to the HP1 via serial port.

RMT MODEL<cr>

I am calculating the checksum incorrectly apparently since I am receiving a response of ERR 242 from the Home Patrol.

Could someone provide an example for this command so I can figure out what I am doing wrong?

I tried as follows:

R - 82 + M - 77 + T - 84 + M - 77 + O -79 + D - 68 + E - 69 + L - 76 Total 612

I also tried 625 (612 + 13<cr>)

The following all result in ERR 242 from Home Patrol

Sending RMT MODEL 612<cr> or RMT MODEL, 612<cr>

Sending RMT MODEL 625<cr> or RMT MODEL, 625<cr>

Any help would be appreciated. Also what does the Serial Port for the Home Patrol Default to when selected and how would I change the Home Patrol Baud Rate it uses when the Serial Port is connected?

Thanks in advance.
 

dfw1417

Member
Joined
Dec 19, 2002
Messages
71
Location
DFW Texas
Checksum ??

Ok I appreciate the help and the links guys, however this Lockbox math just does not add up!

Unless the ASCII chart changed since I last used it I come up with a Checksum of 623 for the below:

RMT<tab>MODEL as follows:

R -82
M - 77
T - 84
Tab - 11
M - 77
O - 79
D - 68
E - 69
L - 76

No matter how many times I add and check the numbers I get 623 NOT 630.as the linked example.

For RMT VERSION I get the following:

R - 82
M - 77
T - 84
Tab - 11
V - 86
E - 69
R - 82
S - 83
I - 73
O - 79
N - 78

This totals 804 NOT 811 as the linked example.

What am I missing here ... These 2 are off by the same value 7 which is a BELL character .. so confused!
 
Last edited:

dfw1417

Member
Joined
Dec 19, 2002
Messages
71
Location
DFW Texas
Checksum - Got it - Thanks!

Thanks, I appreciate it, sometimes its hard to see the forest for the trees!
 
Status
Not open for further replies.
Top