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Read the package length and header with a single read operation.

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This commit is contained in:
Jef Driesen 2007-11-17 08:53:54 +00:00
parent 40e37e6675
commit 5e9279b99d
1 changed files with 7 additions and 14 deletions
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21
suunto_vyper.c
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@ -410,9 +410,10 @@ suunto_vyper_read_dive (vyper *device, unsigned char data[], unsigned int size,
unsigned int nbytes = 0;
for (;;) {
// Receive the header of the package.
unsigned char reply = 0;
rc = serial_read (device->port, &reply, 1);
if (rc != 1 || memcmp (command, &reply, 1) != 0) {
unsigned char header[2] = {0};
rc = serial_read (device->port, header, 2);
if (rc != 2 || memcmp (command, header, 1) != 0 ||
header[1] > SUUNTO_VYPER_PACKET_SIZE) {
// If no data is received at this point (a timeout occured),
// we assume the last package was already received and the
// transmission should be finished. This is not 100% reliable,
@ -425,18 +426,11 @@ suunto_vyper_read_dive (vyper *device, unsigned char data[], unsigned int size,
if (rc == 0 && nbytes != 0)
break;
WARNING ("Unexpected answer start byte(s).");
return EXITCODE (rc, 1);
}
// Receive the size of the package.
unsigned char len = 0;
rc = serial_read (device->port, &len, 1);
if (rc != 1 || len > SUUNTO_VYPER_PACKET_SIZE) {
WARNING ("Unexpected answer length.");
return EXITCODE (rc, 1);
return EXITCODE (rc, 2);
}
// Receive the contents of the package.
unsigned char len = header[1];
unsigned char package[SUUNTO_VYPER_PACKET_SIZE] = {0};
rc = serial_read (device->port, package, len);
if (rc != len) {
@ -446,8 +440,7 @@ suunto_vyper_read_dive (vyper *device, unsigned char data[], unsigned int size,
// Calculate the checksum.
unsigned char ccrc = 0x00;
ccrc = suunto_vyper_checksum (&reply, 1, ccrc);
ccrc = suunto_vyper_checksum (&len, 1, ccrc);
ccrc = suunto_vyper_checksum (header, 2, ccrc);
ccrc = suunto_vyper_checksum (package, len, ccrc);
// Receive (and verify) the checksum of the package.