AMY-6M - Hardware Integration Manual
UBX-17021971 – R07
Design-in
Page 19 of 57
2.3.3
Display Data Channel (DDC)
An I
2
C compatible Display Data Channel (DDC) interface is available for serial communication. For more
information about DDC implementation refer to the
u-blox 6 Receiver Description including Protocol
Specification
Background information about the DDC interface is available in Appendix C.1.
u-blox 6 GPS receivers normally run in I
2
C slave mode. Master Mode is only supported when external
EEPROM is used to store configuration, at this time no other nodes may be connected to the bus. In this
case, the receiver attempts to detect the EEPROM by writing and reading from a specific location.
Pins SDA2 and SCL2 have internal pull-ups. These pull-up resistors integrated in the pads of the baseband-IC are
sufficient for most applications. However, for high capacitive loads, parallel external pull-up resistors need to be
added. Table 6 lists the externally required pull-up resistor values for the DDC interface.
Load Capacitance
Pull-Up Resistor Value R20, R21
50 pF
N/A
100 pF
18 k
250 pF
4.7 k
Table 6: Pull-up resistor values for DDC interface
2.3.3.1
Communicating to an I
2
C EEPROM with the GPS receiver as I
2
C master
Serial I
2
C memory can be connected to the DDC interface as shown in Figure 12. This can be used to
permanently save configuration settings. It will automatically be recognized by firmware. The memory address
must be set to 0b10100000 see Figure 12 (A0, A1 and A2 must be connected to GND), and the size must be to
4 kByte (32 kBit).
The AMY-6M monitors the supply voltage VDD_IO. This implies the I
2
C EEPROM is operating above the VDD_IO
threshold defined for I
2
C EEPROM operation (see Section 2.1.1.6).
Only use I
2
C EEPROM types listed in Table 14
Figure 12: Connecting external serial I
2
C memory used by the AMY-6M to save configuration (see EEPROM data sheet for exact
pin orientation)
In limited cases u-blox 6 GPS receivers can fail to correctly write to external I
2
C EEPROM. To guarantee
successful storage of the configuration into external I
2
C EEPROM, the writing cycles need to be verified by a
read cycle (see
u-blox 6 firmware version 7 Release Notes
[5] for details).
2.3.3.2
Communicating as I
2
C slave to a host
An I
2
C master can communicate with the AMY-6M through the DDC interface.
