What is the latest ROM version for the ISM420? How do I read it?

The base part number is ISM420R1-C33. The ROM Code part number can be read from the GPS in OSP (Sirf Binary) mode only and the version is :  “GS4e -4.1.2-P1”. The GPS will initially come up in OSP at 115200 baud, unless … Continue reading “What is the latest ROM version for the ISM420? How do I read it?”

OPS MID 129 routine (switch from OPS to NMEA) for ISM420-480 EVB

Function: OSPMID129 Description: Send SiRF MID 129 (Switch to NMEA Protocol) to GPS in OSP mode // where: A0A20018 – Start sequence/Payload length // 81020101000101010501010100010001001000012580 – Payload // 01ABB0B3 – Checksum/End sequence // 81 MID // 02 Mode: 00-Enable NMEA … Continue reading “OPS MID 129 routine (switch from OPS to NMEA) for ISM420-480 EVB”

How do I switch from NEMA to the Sirf Protocol on the ISM300?

You need to send a Carriage Return (0x0D) and Line Feed (0x0A) after the checksum (*37) for the SiRF chip to act on the message. Ex: $PSRF100,0,57600,8,1,0*37<CR><LF>

What OSP messages is used to turn the GPS Off ?

The command to turn off the GPS in OSP is Message ID 205 (Sub ID 16). So the actual message is: A0A20002CD1000DDB0B3

Is flash enable required on the GPS? Reset?

The FLASH_EN is only needed to Flash the GPS. Reset is needed is you want to exit Flash mode without powering off the GPS. Otherwise not needed in normal operation The ISM480 powers up in an off state. The On/Off … Continue reading “Is flash enable required on the GPS? Reset?”

What inductor do you use for the RF antenna connection?

The ISM420 requires the use of the following circuit in the front end if you plan on using an active antenna. The circuit is not required if you elect to have no power and use a passive antenna. RFin connects to … Continue reading “What inductor do you use for the RF antenna connection?”

How do I set the data rate of the NEMA messages used?

Here is the function call: /* Set the rate of the NMEA messages used */ PSRF103(“00”, “00”, “01”, “02”); // GGA at 1 sec rate Here is the function: //—————————————————————————– // Function:    PSRF103 // Description: Send SiRF msg 103 to … Continue reading “How do I set the data rate of the NEMA messages used?”

ISM480 GPS UART, SPI and I2C levels

UART MARK (Logic 1) = Logic High Space (Logic 0) = Logic Low Idle Line = Logic High Line-break/open line = Continuous Logic Low SPI Slave Mode Idle Pattern: A7B4 Maximum Clock = 6.8 MHz Default Clock Polarity and Phase: … Continue reading “ISM480 GPS UART, SPI and I2C levels”

ISM480 GPS State of Pins after Reset

After a reset (internally pulled up, power up generates the first reset) and before the first time ON_OFF. Pin      Description      Reset State 1        CTS/SPI_CL/GPIO6      Pad Enabled, Low, Weak Pull-down Enabled 2        RX/MOSI/SDA          Pad Enabled, High 3        TX/MISO/SCL            Pad Enabled, High 4        RTS/SPI_CS/GPIO7        Pad Enabled, High, Weak Pull-up … Continue reading “ISM480 GPS State of Pins after Reset”

How do you change the GPS output rate from a true 1Hz to 5Hz?

To enable the 5 Hz, use OSP MID 136.  The field “Position Calc Mode” can be interpreted this way: Bit Mapped.  When set to 1, a bit enables the function. Bit     Function —-      ———– 0     Almanac Based Positioning 1     Reverse EE … Continue reading “How do you change the GPS output rate from a true 1Hz to 5Hz?”