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Specifications

RasPiGNSS expansion port (P1) connections

P1 Pin GPIO Symbol Description
P1-1 +3.3V Power supply to NV08C digital I/O
P1-2 +5V Analog and digital power supply
P1-4 +5V Analog and digital power supply
P1-6 GND Ground
P1-7 GPIO4 SW1 Tactile switch 1
P1-8 GPIO14 RX1 Serial receive of NV08C, RasPi TXD0
P1-10 GPIO15 TX1 Serial transmit of NV08C, RasPi RXD0
P1-11 GPIO17 SW2 Tactile switch 2
P1-12 GPIO18 RST Reset of NV08C
P1-13 GPIO27 1pps 1pps signal (GPIO1) of NV08C
P1-15 GPIO22 LED1 Red indicator LED
P1-16 GPIO23 LED2 Yellow indicator LED
P1-18 GPIO24 LED3 Green indicator LED

Note: LEDs or switches are not controlled by the NV08C, all I/Os are fully programmable from the RasPi. All LEDs are standard 20mA types and are driven from the RasPi via a MOSFET. Configure pins 15, 16, and 18 as outputs and set them high to switch them on. All switches are directly wired to ground. Enable pullups on pins 7, and 11, and do debouncing in software to read them correctly.

LCD connector

The LCD connector can be used to connect a HD44780-compatible character LCD display to the Raspberry Pi. Its pins are directly connected to Raspberry Pi GPIOs, so you can use them just as standard GPIOs as well. The connector exhibits the standard 14-pin connections, excluding backlight LED anode/cathode connections (which may be connected to +5V and GND pins of other connectors).

Note that the display is driven in 4-bit (nibble) mode in order to save on GPIOs, so you need to do two nibble transfers to send one byte to the character LCD. Note also that functionality is limited to writing the LCD only, as the HD44780 LCD controller works with +5V I/O levels that would damage the Raspberry Pi’s GPIOs when driven for reading. Writing however is no problem as the +3.3V high level of the Raspberry Pi GPIOs fits well to the expected TTL high level of the HD44780. Therefore LCD5 RW is always connected to ground, allowing only write operations to the LCD.

LCD pin P1 pin GPIO Symbol Description
LCD1 P1-6 - GND Ground
LCD2 P1-2, P1-4 - Vcc +5V power supply
LCD3 - - VE LCD contrast adjustment
LCD4 P1-22 GPIO25 RS Register Select (0: command, 1: data)
LCD5 P1-6 - RW Read/¬Write (connected to GND)
LCD6 P1-26 GPIO7 EN Enable (clock, also SPI0_CE1_N)
LCD7 P1-6 - D0 GND (4bit mode)
LCD8 P1-6 - D1 GND (4bit mode)
LCD9 P1-6 - D2 GND (4bit mode)
LCD10 P1-6 - D3 GND (4bit mode)
LCD11 P1-24 GPIO8 D4 D0 (shared with SPI0_CE0_N)
LCD12 P1-21 GPIO9 D5 D1 (shared with SPI0_MISO)
LCD13 P1-19 GPIO10 D6 D2 (shared with SPI0_MOSI)
LCD14 P1-23 GPIO11 D7 D3 (shared with SPI0_SCLK)

Note that you cannot use the LCD and SPI ports at the same time, as all SPI lines are also used by the LCD. When using SPI only, you may however use the remaining GPIOs from the LCD connector (GPIO7 and GPIO25) for other purposes.

SPI connector

The SPI connector allows connecting any supported SPI device to the Raspberry Pi’s SPI0 bus. It uses a standard 2x3 (6-pin) connector with a fairly standard pinout.

Note that while the power supply is +5V, all I/O signals are +3.3V level! Observe compatibility of the SPI device pinout and logic levels, otherwise you may damage your Raspberry Pi!

SPI pin P1 pin GPIO Symbol Description
SPI1 P1-21 GPIO9 SPI0_MISO SPI Master-In Slave-Out
SPI2 P1-2, P1-4 - Vcc +5V power supply
SPI3 P1-23 GPIO11 SPI0_SCLK SPI clock
SPI4 P1-19 GPIO10 SPI0_MOSI SPI Master-Out Slave-In
SPI5 P1-24 GPIO8 SPI0_CE0_N SPI select signal (negated, active low)
SPI6 P1-6 - GND Ground

Note that you cannot use the LCD and SPI ports at the same time, as they share many signals.

I2C connector

The I2C connector provides access to the Raspberry Pi’s I2C1 bus.

I2C pin P1 pin GPIO Symbol Description
I2C1 P1-5 GPIO3 SCL1 I2C clock
I2C2 P1-3 GPIO2 SDA1 I2C data
I2C3 P1-6 - GND Ground
I2C4 P1-1 - +3V3 +3.3V power supply
I2C5 P1-2, P1-4 - +5V +5V power supply

Note that all I2C signals (SCL1, SDA1) have +3.3V logic levels. Connecting to a device with +5V logic levels may damage your Raspberry Pi! The I2C5 +5V pin is provided for convenience only, e.g. for devices providing an internal voltage regulator (as some Pololu IMUs do). There are two on-board 4k7 pull-up resistors for SDA and SCL of the I2C bus, which can be activated by shortening two solder bridges located between the big goldcap and the right push button on the top side of the Aldebaran board.

NV08C 2nd serial port connector

The SER connector provides access to the second serial port of the NVS NV08C-CSM GNSS chip on the RasPiGNSS “Aldebaran”.

SER pin Symbol Description
SER1 TX2 NV08C port 2 serial transmit
SER2 RX2 NV08C port 2 serial receive
SER3 GND Ground
SER4 +3V3 +3.3V power supply
SER5 +5V +5V power supply

Note that all SER signals have +3.3V logic levels. Connecting to a device with +5V logic levels may damage the NV08C-CSM chip of the RasPiGNSS! The SER5 +5V pin is provided for convenience only, e.g. for devices providing an internal voltage regulator.

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