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(New page: == What is GPS == The Global Positioning System (GPS) is a a satellite positioning system, using a constellation of 31 satellites. GPS uses these as "man-made stars" to calculate positio...) |
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− | == | + | == GPS的內容 == |
− | + | GPS (Global Positioning System)是一個衛星定位系統,使用31個衛星。 | |
− | GPS | + | GPS 類似 "人造衛星" ,以公尺為計算單位。某些形態的GPS,可以較公分為佳的單位進行度量。 |
− | + | 利用先進的科技,從IC及其它的元件中接收訊號。 | |
− | + | 它大量的降低了成本。 | |
− | + | 因為它大量降低成本的特性,它可以輕鬆的被整合到手機、筆記型電腦及像是耕作用具、瀏覽系統及建築物...等傳統工具中。tion systems and construction equipment. | |
− | ( | + | (你可以在這個位址[http://www.colorado.edu/geography/gcraft/notes/gps/gps_f.html Global Positioning System Overview]取得其它的相關資訊。) |
== [[Hardware:AGPS|AGPS]] == | == [[Hardware:AGPS|AGPS]] == | ||
− | + | 這個分類中可以找到[[Hardware:AGPS|所有GPS的資訊]]. | |
== PMB 2520 Hammerhead == | == PMB 2520 Hammerhead == |
Revision as of 12:14, 27 May 2008
Contents |
GPS的內容
GPS (Global Positioning System)是一個衛星定位系統,使用31個衛星。
GPS 類似 "人造衛星" ,以公尺為計算單位。某些形態的GPS,可以較公分為佳的單位進行度量。
利用先進的科技,從IC及其它的元件中接收訊號。
它大量的降低了成本。
因為它大量降低成本的特性,它可以輕鬆的被整合到手機、筆記型電腦及像是耕作用具、瀏覽系統及建築物...等傳統工具中。tion systems and construction equipment.
(你可以在這個位址Global Positioning System Overview取得其它的相關資訊。)
AGPS
這個分類中可以找到所有GPS的資訊.
PMB 2520 Hammerhead
The PMB 2520 Hammerhead is a one-chip solution for GPS that is produced by Infineon Technologies in cooperation with Global Locate. It allows the usage of assistance data by supporting A-GPS standards.
(all infomation is coming from the datasheet of PMB 2520) short datasheet
Modules of the Hammerhead
The Hammerhead consists of the following modules:
- RF front-end with on-chip, high gain and low noise, LNA, I/Q mixers, on-chip polyphase complex IF filter, digitally controlled AGC, and 3-bits ADC for the I and Q paths.
- Sigma-Delta RF PLL with on-chip PCO and on-chip loop filter.
- Embedded PLL and NCO for baseband clock generation.
- Multiple channels digital mixers and parallel correlator engines to enable real time correlation of the PRN code for up to 14 satellites.
- Post processor including peak detection logic
- SRAM for storing correlation results
Host Interface
The Hammerhead integrates 3 serial interfaces:
- UART
- I2C
- SPI
The UART in the Hammerhead is a full-duplex UART interface. It is fixed in 8N1(8 data bits, no parity, 1 stop bit) mode. On the GTA01, the host processor connect with the Hammerhead through the UART. In all models of Neo1973, this is connected to a serial port.
Host software Architecture
The Hammerhead driver software will be delivered as a binary, which can be interfaced to gpsd as it outputs NMEA information, as many serial GPSs do.
The gps driver is now available. (There were some problems in the past getting a license to distribute the binary. [1])
The gpsd libraries provide the following infomation to the high level software:
- Position data
- Library status
- Time-out and Packet Available
The high level software sends the following messages to the plugin:
- Assistance data
- Positioning Commands
- Configuration Commands
Gpsd communicates with the system at the following part:
- Communications Drivers
- System Timer
- NV storage
- Log buffer
GPS on GTA01
At the GTA01, the host processor is a S3C2410.
Hammerhead on the GTA01
On the GTA01, the Hammerhead are configured that connected with the host processor through the UART. The UART of data output/input is connected to the UART 1 of the SC2410. The UART of the hardware flow control is connected to the UART 2 of the SC2410.
Q & A
Q: Can gpsd support Differential GPS.
- While the neo does not have any means of receiving DGPS or WAAS/SCCM directly, it can be streamed from an internet server.
- It may be possible to generate a global ionospheric model from stationary (charging?) neos that have GPS signal and cheap internet connections. This would enable very precise positions to be generated
- This could generate positions accurate to well under a metre, compared to (probably) 2-3m without.
- The gpsd plugin is the place that these corrections would need to be done, as they need to be performed on a per-satellite basis, before generating the position.
- This is separate from AGPS - AGPS gives information on current satellite position, or computes your position for you. DGPS is a local minute by minute 'ionospheric weather' for your region.
See also Server:A-GPS.
Q: Can someone upload somewhere an strace of the interaction between gpsd, and the hammerhead chip?
- Ideally this would be requesting a GPS position every second, starting from 'cold', with no AGPS data, for at least half an hour, in an area where the reciever can see the sky.
- To aid in reverse engineering efforts.
- A reverse-engineering page has been created: Hammerhead/Protocol
Q: Can I get NMEA data from the GPS?
A: Not directly. However, the gpsd program 'gpspipe', with the -r switch will output NMEA data with the current position information. The right way to do it is to use libgpsd in your program if possible.
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