ZED-F9P - Integration manual
R11 = 100 k Ω is recommended
R4, R5 = 27 Ω is recommended
3.7 Predefined PIOs
In addition to the communication ports, there are some predefined PIOs provided by ZED-F9P to
interact with the receiver. These PIOs are described in this chapter.
3.7.1 D_SEL
The D_SEL pin can be used to configure the functionality of pins 42 to 45 . It is possible to configure
the pins as UART1 + I2C, or as SPI. SPI is not available unless D_SEL pin is set to low. See
below.
Pin No
D_SEL == 0
D_SEL == 1
42
SPI_MISO
UART1 TXD
43
SPI_MOSI
UART1 RXD
44
SPI_CS_N
I2C SDA
45
SPI_CLK
I2C SCL
Table 23: D_SEL configuration
3.7.2 RESET_N
The ZED-F9P provides the ability to reset the receiver. The RESET_N pin is an input-only pin with an
internal pull-up resistor. Driving RESET_N low for at least 100 ms will trigger a cold start.
The RESET_N pin will delete all information and trigger a cold start. It should only be used
as a recovery option.
3.7.3 SAFEBOOT_N
The ZED-F9P provides a SAFEBOOT_N pin that is used to command the receiver safe boot mode.
If this pin is low at power up, the receiver starts in safe boot mode and GNSS operation is disabled.
The safe boot mode can be used to recover from situations where the flash content has become
corrupted and needs to be restored.
In safe boot mode the receiver runs from a passive oscillator circuit with less accurate timing and
hence the receiver is unable to communicate via USB.
In this mode only UART1 and I2C communication is possible. For communication via UART1 in safe
boot mode, the host must send a training sequence (0 x 55 55 at 9600 baud) to the receiver in order
to begin communication. After this the host must wait at least 2 ms before sending any data.
It is recommended to have the possibility to pull the SAFEBOOT_N pin low in the application. This
can be provided using an externally connected test point or a host I/O port.
3.7.4 TIMEPULSE
The ZED-F9P high precision receiver provides a time pulse on the TIMEPULSE pin.
UBX-18010802 - R08
3 Receiver functionality
Page 42 of 110
Early production information
