I wonder if the Sony unit would perform better with a cable attached to separate the GPS further from the PSP. Id bet that interference could be an issue, being so close to the PSP.
If you had a user that had both Mapthis and the Japanese mapping software, you could rule out the software and focus on improving the psp-290.
Also, It would be interesting to know if the PSP-290 recieves any commands from the PSP, such as NMEA sentences for "Hot Start", "Warm Start", "Cold Start".
Sometimes those commands start with $PSRF, or Sony could use proprietary commands. Surely they anticipated homebrewers using the unit, and had plenty of time to throw in some curveballs.
Im just going to cut and paste some text from
http://www.gpsinformation.org/dale/nmea.htm#proprietary
SiRF
The SiRF line of chips support several input sentences that permit the user to customize the way the chip behaves. In addition SiRF has a binary protocol that is even more powerful permitting different implementations to behave entirely differently. However, most applications do not attempt to customize the behavior so a user will need to make sure that the any customization is compatible with the application they are planning to use. There are 5 input sentences defined that begin with $
PSRF which is followed by three digits. Each sentence takes a fix amount of input fields which must exist, no null fields, and is terminated with the standard CR/LF sequence. The checksum is required.
The sentences 100 and 102 set the serial ports. 100 sets the main port A while 102 sets the DGPS input port B. 100 has an extra field that can be used to switch the interface to binary mode. Binary mode requires 8 bits, 1 stop bit, no parity. There is a command in binary mode that will switch the interface back to
NMEA. Do not use the
NMEA command to switch to binary mode unless you have the ability to switch it back. You could render your gps inoperative. $PSRF100,0,9600,8,1,0*0C $PSRF102,9600,8,1,0*3Cwhere $PSRF100 0 0=SiRF, 1=
NMEA - This is where the protocol is changed. 9600 b/s rate 4800, 9600, 19200, 38400 8 7, 8 Databits 1 0, 1 Stopbits 0 0=none, 1=odd, 2=even Parity *0C checksum
The sentences 101 and 104 can be used to initialize values to be used by the gps. Supplying these values can shorten the initial lock time. If the clock offset is set to 0 then an internal default will be used. Sentence 101 supplies data in the internal ECEF (Earth centered, Earth Fixed) format in meters while sentence 104 supplies the data in the traditional Lat / Lon format. $PSRF101,-2686700,-4304200,3851624,95000,497260,921,12,3*22 $PSRF104,37.3875111,-121.97232,0,95000,237759,922,12,3*3Awhere $PSRF104 37.3875111 Latitude in degrees -121.97232 Longitude in degrees 0 Ellipsoid Altitude in meters 95000 Clock offset 237759 GPS Time of Week in seconds 922 GPS Week Number 12 Channel count (1 to 12) 3 Reset config where 1 = warm start, ephemeris valid 2 = clear ephemeris, warm start (First Fix) 3 = initialize with data, clear ephemeris 4 = cold start, clear all data 8 = cold start, set factory defaults *3A checksum
The sentence 103 is used to control which
NMEA sentences are to be sent and how often. Each sentence type is controlled individually. If the query bit is set then the gps responds by sending this message in the next second no matter what the rate is set to. Note that if trickle power is in use (can only be set in binary mode) then the actual update rate will be the selected update rate times the trickle rate which could mean that the data will be sent less frequently than was set here. $PSRF103,05,00,01,01*20where $PSRF103 05 00=GGA 01=GLL 02=GSA 03=GSV 04=RMC 05=VTG 00 mode, 0=set rate, 1=query 01 rate in seconds, 0-255 01 checksum 0=no, 1=yes *20 checksum
The 105 sentence controls a debug mode which causes the gps to report any errors it finds with the input data. $PSRF105,1*3E would turn debug on while $PSRF105,0*3F would turn it off.
Sony
The
Sony interface uses a proprietary sentence that looks like: $PSNY,0,00,05,500,06,06,06,06*14where PSNY 0 Preamp (external antenna) status 0 = Normal 1 = Open 2 = shorted 00 Geodesic system (datum) 0-25, 0 = WGS84 05 Elevation mask in degrees 500 Speed Limit in Km 06 PDOP limit with DGPS on 06 HDOP limit with DGPS on 06 PDOP limit with DGPS off 06 HDOP limit with DGPS off *14 Checksum
Sony $GPVTG,139.7,T,,M,010.3,N,019.1,K*67$GPGGA,050306, 4259.8839,N,07130.3922,W,0,00,99.9,0010,M,,M,000,0 000*66$GPGLL,4259.8839,N,07130.3922,W,050306,V*20$ GPRMC,050306,V,4259.8839,N,07130.3922,W,010.3,139. 7,291003,,*10$GPZDA,050306,29,10,2003,,*43$GPGSA,A ,1,,,,,,,,,,,,,99.9,99.9,99.9*09$PSNY,0,00,05,500, 06,06,06,06*14Some observations
- This is the format of Digittraveler from RadioShack.
- If batteries are removed for 5 minutes on the Digitraveler the data is wrong.
- The Sony proprietary message is described above.
- Altitude is Ellipsoid, not MSL.
- Heading is True only, Magnetic variation is not provided.
- VTG, GGA, GLL, RMC, ZDA output every second. GSA and PSNY are alternated with GSV data.
Has anyone cracked the unit open to see if they can tweak the antenna?
I think someone is going to have to a) find out what chip they used
b) Find out what software commands are/could be issued to the unit.
