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$NetBSD: patch-af,v 1.1 2009/02/08 15:30:26 gdt Exp $
From Giles Lean, who places it in the public domain. Workarounds for
problems with buggy USB serial adapators.
--- jeeps/gpsread.c.orig 2006-04-19 22:20:18.000000000 -0400
+++ jeeps/gpsread.c
@@ -103,6 +103,37 @@ int32 GPS_Serial_Packet_Read(gpsdevh *fd
if(!len)
{
+ /*
+ * Missed DLE characters have been observed with Geko
+ * 201 and Legend GPSRs with Prolific USB-serial
+ * cables. The following kludge seems to help.
+ *
+ * It has been tested so far with the following
+ * combinations of software and hardware:
+ *
+ * OS X 10.4.x and 10.5.x:
+ *
+ * - a Geko 201 (firmware version 2.70) and a third
+ * party cable using a Prolific USB-serial converter
+ * - a Legend using a serial cable with a non-integral
+ * Prolific USB-serial converter.
+ *
+ * NetBSD-4.0/i386 with the Geko and cable as above.
+ *
+ * REVISIT GFL Should this be a switch in a .ini file?
+ *
+ * + it's a kludge, so leaving it always on is ugly
+ * - if it's harmless to properly working hardware,
+ * then it's a better user experience to leave it on
+ */
+ if (u == 0x06 || u == 0x15)
+ {
+ (*packet)->dle = DLE;
+ ++len;
+ (void) fprintf(stderr,"GPS_Packet_Read: inserted DLE due to 0x%02x.\n", u);
+ goto dle_missed;
+ }
+
(*packet)->dle = u;
if(u != DLE)
{
@@ -114,6 +145,7 @@ int32 GPS_Serial_Packet_Read(gpsdevh *fd
continue;
}
+dle_missed:
if(len==1)
{
(*packet)->type = u;
@@ -212,6 +244,20 @@ int32 GPS_Serial_Get_Ack(gpsdevh *fd, GP
if(*(*rec)->data != (*tra)->type)
{
+ /*
+ * When used with a buggy Prolific USB-serial converter the
+ * calling sequence GPS_A000() -> GPS_Get_Ack() sometimes
+ * returns data != type causing this routine to fail and the
+ * following error message to be emitted:
+ *
+ * GARMIN:Can't init /dev/cu.usbserial
+ *
+ * Manually retrying usually works, and subsequent
+ * investigation shows that the call that fails is made from
+ * GPS_Init() which in this case is GPS_Serial_Init(). Simply
+ * retrying the call a workaround: see note and retry loop in
+ * gpsapp.c:GPS_Init().
+ */
gps_error = FRAMING_ERROR;
return 0;
}
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