LEA-5, NEO-5, TIM-5H - Hardware Integration Manual
GPS.G5-MS5-09027-A2
Released
Hardware description
Page 15 of 68
Load Capacitance
Pull-Up Resistor Value R20, R21
50 pF
18 k
100 pF
9 k
250 pF
4 k
Table 3: Pull-up resistor values for DDC interface
Serial I
2
C memory can be connected to the DDC interface. It will automatically be recognized by firmware. The
memory address must be set to 0b1010000 and the size fixed to 4 kB.
u-blox 5 M odule
EEPROM
SDA2
SCL2
SDA
SCL
VDD
VDD_IO
VDD
R20
VDD_IO
VDD_IO
R21
A0
A1
A2
WP
Figure 6: Connecting external serial I2C memory used by the GPS receiver (see data sheet for exact pin orientation)
Note that the case shown on Figure 6 is different than the case when EEPROM is present but used by external
host / CPU as indicated on Figure 7. This is allowed but precaution is required to ensure that the GPS receiver
does not detect the EEPROM device, which would effectively configure the GPS receiver to be MASTER on the
bus causing collision with the external host.
To ensure that the EEPROM device (connected to the bus and used by the host) is not detected by the GPS
receiver it is important to set the EEPROM‖s address to a value different than 0xA0. This way EEPROM remains
free to be used for other purposes and the GPS receiver will assume the SLAVE mode.
Ensure that at the start up the host allows enough time for the receiver to communicate over the bus to
establish presence of the EEPROM. It is only when this interrogation is complete that the host can
exercise full control over the bus (MASTER mode).
Also note that the FLASH based modules do not attempt to store any information in the external
EEPROM and as such do not attempt to communicate to the external EEPROM. The ROM based
receivers always interrogate external EEPROM at the start-up. The interrogation process is guaranteed to
complete within 250ms upon start up. This is the time the external host has to give to the ROM based
GPS receiver to complete the EEPROM interrogation.
Although the FLASH based modules do not attempt to detect the EEPROM at the start up, an attempt to
communicate to the GPS receiver via DDC before 250msec expires is not advised because the GPS
receiver is unable to respond due to other start up activities.
