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Cards System Summary


'Longan Cards' is a unique open source development platform developed by Longan Labs. As a plug and play development platform, Longan cards allow you to quicky build wide array of prototypes and applications in no time. A full set of Arduino libraries and plenty of example codes are available to play with Longan cards platform.

NOTE: Most of the Longan cards are based on the I2C communication protocol.

Longan cards fall into following categories:

  • Sensor
  • Actuator
  • Controller
  • Display
  • Communication
  • Support

You can use Longan Cards with following Longan boards.

  • Game board
  • Extension board
  • Car board
  • Sensor board
  • Pi Hap

All cards that support I2C communication protocol comes with a unique factory default I2C address can be found on the back of the card.

Cards and Boards

Following table presents the type, I2C address, and communication protocol of each Longan card.

SKU Name Type I2C address Coomunication Protocol
1011001 Temperature Card Sensor 0x01 I2C
1011002 Sound Sensor Card Sensor 0x02 ADC
1011003 PIR Sensor Card Sensor 0x03 I/O
1011004 Gesture Sensor Card Sensor 0x04 I2C
1011007 Rotary Angle Card Sensor 0x07 ADC
1011008 BME280 Card Sensor 0x08 I2C
1011010 Light Sensor Card Sensor 0x0A ADC
1011012 RTC Card Sensor 0x0C I2C
1011021 9-Dof Sensor Card Sensor 0x15 I2C
1011027 Button Input Card Sensor 0x1B I/O
1011028 VOC&eCO2 Gas Sensor Sensor 0x1C I2C
1011029 IR Recever Card Sensor 0x1D 其他协议 (Other)
1011032 Line Finder Card Sensor 0x1E 其他协议 (Other)
1012001 Relay Card Actuator 0x41 I/O
1012002 Buzzer Card Actuator 0x42 I/O
1012003 Motor Driver Card Actuator 0x43 I/O
1013001 Carduino 328 Controller -
1013007 Carduino 32U4 Controller -
1014001 OLED Card Display - SPI
1015003 IR Emitter Card Communication 0x44 其他协议 (Other)
1016006 Programmer Card Support -
1016007 AAA Battery Card Support -
1017002 Extension Board Board -
1017006 PI Hap for Longan Card Board -
1017007 Sensor Display Board -
1017008 Game Board -
1017009 Car Board Board -


The edge connector (gold fingers) has total of 30 contacts (each side has 15 contacts).

On the front side of the temperature card, a white arrow is printed near the edge connector indicates the pin #1. You can find some pin numbers printed on the edge connector itself (1, 15, and 29). You can count the pin numbers starting with 1 and count by twos from right to left would be 1, 3, 7, 9, 11, 15, 17, 19, 21, 23, 27, and 29. Notice that all the counts are odd numbers.

On the back side of the temperature card, you also can find some pin numbers printed on the edge connector itself (2, 16, and 30). You can count the pin numbers starting with 2 and count by twos from left to right would be 2, 4, 6, 8, 10, 12, 14, 16, 18, 20, 22, 24, 26, 28 and 30. Notice that all the counts are even numbers.

The gold fingers of each Longan card exposes all or subset of pins shown in the following figure.


This is the general purpose I/O pin set for the Carduino. GPIO consists of digital, analog, I2C, SPI, and UART pins. Most pins can do PWM output. Also, all pins can be used as interrupt pins.

  • Digital (Front: pin #9, #11, #21 / Back: pin #10, #12, #22)
  • Analog (Front: pin #13, #19 / Back: pin #14, #20)

NOTE: Motor driver card uses analog pins to drive two motors.

I2C Pins

Following pins can be used for I2C communication.

  • SDA: Digital I/O, I2C bus serial bidirectional data line (Front: pin #5, #25 / Back: pin #6, #26)
  • SCL: Digital Input, I2C bus serial clock input (Front: pin #7, #23 / Back: pin #8, #24)

Power Pins

Following pins connect with the common power bus of the board.

  • VCC: Power supply (Front: pin #1, #29 / Back: pin #2, #30)
  • GND: To be connected to the system ground (Front: pin #3, #27 / Back: pin #4, #28)

Hardware SPI Pins

These are the hardware SPI pins that can be used to communicate with high speed.

  • SCK – Serial Clock (Front: pin #17)
  • MISO - Master In Slave Out, takes data from the Carduino to the SPI device (Front: pin #15)
  • MOSI – Master Out Slave In, takes data to the Carduino from the SPI device (Back: pin #16)

Hardware UART / Serial Pins

These pins can be used to connect devices support with UART using two wires.

  • TX – Transmits data, connects with Carduino RX (Back: pin #22)
  • RX – Receives data, connects with Carduino TX (Front: pin #21)

NOTE: The pin functions of Carduino is exactly same with the pin functions of Arduino Leonardo.

How to Use

A card can be plugged into an edge connector slot of one of the following Longan boards.

  • Game board
  • Car board
  • Sensor board
  • Extension board
  • Pi Hap

When you plugging, the white arrow head printed on the card should be pointing toward the white arrow head printed near the edge connector slot of the board. Once plugged, it can communicate with the Carduino through the I2C bus line of the board. It will also connect to the common power bus of the board.

I2C in Depth

Some of the Longan cards (all sensor, actuator, and communication cards) use I2C interface to communicate with the Carduino. They use I2C for read/write data and share the same I2C register. This allows you to use a single code to read data from all the sensor cards. Following table presents the typical I2C register map of a Longan card.

Address Name Type Reset Value Lenght (Byte) Description
0x01 DEVID R \ 1 Device ID
0x02 SENSOR_CNT R \ 1 Number of sensors on the card
0x03 SEN_NAME_LENGTH R \ 1 Length of the name
0x04 ADDR R/W \ 1 Device I2C address
0x10 NAME R \ MAX 20 Device name
0x11 SKU R \ 4 Device SKU
0x12 VERSION R \ 4 Version
0x30 VALUE_0 R \ 6 Sensor 0
0X35 VALUE_5 R \ 4 Sensor 5

Register Definitions

Register 0x01 – DEVID (Read Only)

Card ID.

Return: 1 byte

Register 0x02 - SENSOR_CNT (Read Only)

Number of sensors on the board. As an example, the BME280 card has 4 sensors: temperature, humidity, pressure and altitude. Therefore the SENSOR_CNT value for BME280 card is 4.

Return: 1 byte

Register 0x03 - SEN_NAME_LEN(Read Only)

Length of the card name.

Return: 1 byte

Register 0x04 – ADDR (Read/Write)

I2C Address of the card.

Return: 1 byte

Write: 1 byte

Register 0x10 – NAME (Read Only)

Name of the card as a string, max 20 bytes.

Return 1~20 byte(s)

Register 0x11 – SKU (Read Only)

SKU of the card

Return: 4 bytes

Register 0x12 – VERSION (Read Only)


Return: 4 bytes

Register 0x30-0x3F: VALUE_n

Sensor value

Return: 6 bytes, define as below:

1 2 3 4 5 6