PSAS/ GlobalPositioningSystem

LV2 GPS CAN Node Information

Current GPS Receiver:

Jupiter Board Setup information:

Messages used:

# Name Data we get
1000 Geodetic Position Status Lock, UTC, Lat, Lon, Alt, expected error
1003 Visible Sattelites Best possible xDOP's
1009* ECEF Position ECEF X,Y,Z and Vx, Vy, Vz
1102 Measurement Time Mark Message code and carrier phase data

* - Message # 1009 is called 1001 in v1.18 firmware and earlier

CAN Node Notebook:

05/20020 DY soldered up CAN node. Due to miscommunication, 2mm connector was on wrong side. Corrected. Added red LED on D0. Added 7805 in place of 78L05.
08/25/2002 Programmed both Jupiter boards (v1.18 and v2.30) using LABMON. Seems to have programmed into the EEPROM.
08/26/2002 The Jupiter board we have has a straight through OSX connector for the GPS antenna. This sucks since turns out the OSX cable connector sticks way out of the connector... it requires at least 0.625" to take OSX plug out... less if you don't have to remove it. I used the FC's 0.625 stand offs as a temporary measure - seems to work. Can modify in the future. However, the longer inter-board distance meant that the 2mm connector to the Jupiter board no longer reached - I had to put 2mm pins on the CAN node and use a 20mm 1.5" ribbon cable to connect it.
08/26/2002 Tried out board with PIC in reset. 260mA - which is about right, consider 220mA for the receiver, with 40mA left over for the PIC and active antenna. New problem: power drop in the 7805 = (12V - 5V)*(0.260A) = 1.82W! Duh! Next time, do the loss calculation BEFORE hand. The only quick fix solution I see is either running it off a seperate 6V (puke) or getting a small DC-DC converter to replace the 7805.
08/26/2002 Found a bunch of TI "7805 replacement" SPS's. TI part # 78SR105 (PDF below), Digikey has them. They're huge (8 x 23 x 24 mm) but c'est la vie. There were others, but they were either bigger (the PT series) or had worse ripple (78STxxx series). Mounting is going to be a real problem... i don't want to have to add another board, and there isn't any real screw mounting options... it looks like double sticky foam tape is going to save the day again!
08/27/2002 Got the 78SR105 today and it worked great. Takes in 12V at 140mA and puts out 5V at 260mA which is about 77% efficient (it's burning off roughly 380mW). Tim found a great way to mount it on the board so that two of the pins of the thing could be soldered directly on the board. I chose to use clear silicone to mount it to the board since sticky tape couldn't be found, and it should be a lot stronger since there's not much surface area for the sticky tape. After about 5 minutes of running, the SPS got slightly warm, but not as warm as the GPS main processor! Eventually, after the PIC's mod wires are siliconed down, we really out to zip tie the SPS down for safety.

Safety thoughts on the GPS:

  1. ALWAYS have an ACTIVE antenna connected when the Jupiter board is on.
  2. Make SURE the PIC's port pins are configured properly.

Other links and information:

GPS Antennas:

GPS Antenna Combiners:

Other:

GPS Antenna Pre-amplifiers

Notes on future GPS boards:

Other Links:

Attachments: