NOTE : When the power of device (module) is removed, any modified setting will be lost and reset to factory default setting. MiniGPS is a tool from MediaTek to view the status of GPS receiver more conveniently and also acts as an interface to change the basic setting of GPS receivers. $ PMTK 220 ,3000 * 1D -> Set Position fix interval as 3000ms $ PMTK 605 * 31 -> Query Firmware info (Note that this is a query command and has no datafield) Here are some more commands that we tried on our GPS Dongle
The commands can be given serially via any terminal software like Realterm. To ease the process, you can use NMEA Checksum calculator. It needs to be recalculated every time you change the contents of the command so simply changing the Datafield will not work. It is calculated by XORing all the characters between $ and *. The is a checksum number 34 & 30 are used by the GPS to determine whether it has received the sentence accurately.In the second command, datafield 0,1,5,0,0,0,0,0,0,0,0,0,0,0 indicates that RMC will be output once every 1 position fix and VTG will be output once every 5 position fix updates The Datafield i.e, 0,1,1,0,0,0,0,0,0,0,0,0,0,0 indicates that RMC and VTG sentences will be output once every 1 position fix updates.Many other commands and their packet number are available. Here the packet type i.e, 314 indicates that the command is to Set NMEA sentence output frequencies.Preamble Talker ID Pkt Type Data Field * CHK1 CHK2 CR LF
The PMTK commands are all send in a specific packet format which is shown below. It enables configuring the parameters of the GNSS chipset, aiding assistance position information and receive notifications from the GNSS chip. PMTK command is MediaTek proprietary data transfer protocol for GNSS. The following are command sets for some of the common chipsets To configure a GPS receiver, it is important to know the chipset your GPS is using.
It is possible for the user to customize the output by sending commands over a serial interface to a GPS receiver. that determine the output of the receiver.
Each GPS chip comes hard-programmed with certain parameters like update rate, baud rate, sentence selection, etc.