Pioneer 3™ Pioneer 2™ H8- Series Operations Manual

ActivMedia Robotics Operating System
Data types are simple and depend on the element (see descriptions below): client
commands, SIP types, and so on, are single 8-bit bytes, for example. Command
arguments and SIP values may be 2-byte integers, ordered as least-significant byte
always first. Some data are strings of up to a maximum 200 bytes, prefaced by a length
byte. Unlike common data integers, the two-byte checksum appears with its mostsignificant
byte first (opposite order).
Packet Checksum
Calculate the PSOS/P2OS/AROS client-server packet checksum by successively adding
data byte pairs (high byte first) to a running checksum (initially zero), disregarding sign
and overflow. If there is an odd number of data bytes, the last byte is XORed to the
low-order byte of the checksum.
int calc_chksum(unsigned char *ptr) // ptr is array of bytes
{ // first is data count
int n;
int c = 0;
n = *(ptr++); /* Step over byte count */
n -= 2; /* don't include checksum word */
while (n > 1)
{
c += (*(ptr)