Ublox EVK-NINA-B4, Руководство пользователя

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EVK-NINA-B4 - User guide
UBX-19054587 - R03 Interfaces and peripherals Page 28 of 38
C1 - Public
Powering considerations
Two voltage nets are used in the Raspberry Pi interface, 3V3_PI and 5V . Both the 3V3_PI and 5V nets
can be used to power HATs, but these nets should not be used when connecting to a Raspberry Pi.
See section 4.1.6 for more information.
⚠
Do not connect the 3V3_PI power net m to the 3.3 V supply when connected to a Raspberry Pi
board. Failure to observe this can cause serious damage to both boards.
UART
The Raspberry Pi interface provides two pins that can be used for UART communications GPIO14 and
GPIO15 .
In UART communications, signals are always connected RX <-> TX and vice versa. This means that
GPIO14 is TX on a Raspberry Pi board, but RX and on a HAT. To support communication with both
HATs and Pi boards, the zero
Ω
resistors (R57, R58, R59 and R60) can be used to toggle the NINA TX
and RX pins between
GPIO14
and
GPIO15
. If a NINA-B40 is used, this switch can also be made in the
software. By default, the EVK-NINA-B4 is configured to simulate a HAT, with
GPIO14
connected to
the NINA UART_RXD pin and GPIO15 connected to the NINA UART_TXD pin.
EEPROM support
The Raspberry Pi interface supports a unique EEPROM solution that stores the HAT specific GPIO
configurations on the HAT board. The Raspberry Pi reads the configurations before configuring its
GPIOs. The two pins used for this,
ID_SD and ID_SC , are connected to the NINA-B4 module. In this
way, the NINA module can either read the GPIO configuration from a HAT, or simulate an EEPROM
and send configurations to a connected Pi. This requires a NINA-B40 module and a custom built
application.
The EEPROM solution is not mandatory. If this approach considered inappropriate, do not configure
GPIO_42 and GPIO_41 .
Two pull-up resistors, R44 and R50, can be added to the I2C lines if needed. These pins are not
mounted on the evaluation board by default.
For more information on the ID EEPROM specification, see the raspberrypi/hats pages at github.
5.4 Additional Interfaces
In addition to the normal interfaces most commonly used, there are several other few expansion
options available to the user. These extra interfaces require some modifications to the EVB before
they can be used.