ZED-F9T-Integration Manual
There are additional hardware requirements if USB is designed in to be used:
In self powered mode the receiver is powered by its own power supply. V_USB is used to detect the
availability of the USB port, i.e. whether the receiver is connected to a USB host.
• Pin 38, V_USB needs to be powered by a separate LDO enabled by module VCC and supplied by
the USB host.
• A pull down resistor is required on the output of this V_USB LDO
• V_USB (pin 38) requires 1 µF and 100 nF capacitors mounted adjacent to the pin to ensure
correct V_USB voltage detection
• Apply USB_DM and USB_DP series resistors; typically 27 Ω
Figure 10: ZED-F9T V_USB supply
R11 = 100 k
Ω
is recommended
R4, R5 = 27 Ω is recommended
3.3.4 D_SEL interface
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 + I
2
C, or as SPI. See Table 14 below.
Pin No D_SEL == 0 D_SEL == 1
42 SPI_MISO UART1 TXD
43 SPI_MOSI UART1 RXD
44 SPI_CS_N
DDC/I
2
C SDA
45 SPI_CLK
DDC/I
2
C SCL
Table 14: D_SEL configuration
3.3.5 RESET_N interface
The ZED-F9T high accuracy timing receiver 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 trigger a cold start and therefore should only be used as a recovery
option and not a Power On Reset.
3.3.6 SAFEBOOT_N interface
The ZED-F9T high accuracy timing receiver provides a SAFEBOOT_N pin that is used to command
the receiver into safe boot mode.
If this pin is low at power up, the receiver starts in safe boot mode and GNSS operation is disabled.
It can be used to recover from situations where the Flash has become corrupted and needs to be
restored.
UBX-19005590 - R01
3 Receiver functionality Page 24 of 80
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