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I2C Support on LUCID Cameras

Introduction

This document will discuss using Inter-Integrated Circuit (I2C) communication with LUCID cameras.

Equipment Used
  • PHX032S, Phoenix 3.2MP Sony IMX265, firmware 1.29.0.0
  • GPIO-8P20, 8-pin 20cm JST cable
  • SEN-13762, SparkFun IMU Breakout – MPU-9250 Board (DigiKey: 1568-1420-ND)
  • Arena SDK for Windows v1.0.9.1 or newer
Function Summary

In LUCID’s I2C implementation, the non-opto isolated pins (Line 2 and Line 3 on Phoenix) can be used for the I2C Serial Clock (SCL) and I2C Serial Data (SDA) pins.

If the non-opto pins are used for I2C communication, the pins will not be available for regular triggering or line output. Use the opto-input (Line 0 on Phoenix) for trigger input or the opto-output (Line 1 on Phoenix) for line output.

The camera features I2C Register Address and the I2C Slave Address can be configured to configure the register address to read and the slave address to use.

  • The I2C Register Address Length can be 8-bits (0 – 0xFF) or 16-bits (0 – 0xFFFF)
  • The I2C Slave Address Length can be 7-bits (0 – 0x7F)
I2C Example Setup

The following diagram shows connecting the Phoenix GPIO to a Sparkfun IMU Breakout board with an MPU-9250 sensor.

IC2 GPIO circuit layout
Phoenix camera with I2C support

The following connections are shown in the above images:

Phoenix GPIO Pin Description SEN-13762
Pin2 (Brown) Non-isolated bi-directional GPIO channel (Line2) SCL
Pin4 (Brown) Non-isolated bi-directional GPIO channel (Line3) SDA
Pin3 (Orange) VDD GPIO (2.5V Power Output) (Line 4) VDD
Pin5 (Black) GND (Camera GND) GND

Specifications Tested:

  • SCL / I2C serial clock: 400 kHz
  • Voltage: 5V
Reading with I2C

The following registers will be read from the MPU-9250 sensor (https://www.invensense.com/download-pdf/mpu-9250-register-map/):

Address (Hex) Register Name Description Length (bits)
3B ACCEL_XOUT_H Accelerometer X-Axis high bytes 8
3C ACCEL_XOUT_L Accelerometer X-Axis low bytes 8
3D ACCEL_YOUT_H Accelerometer Y-Axis high bytes 8
3E ACCEL_YOUT_L Accelerometer Y-Axis low bytes 8
3F ACCEL_ZOUT_H Accelerometer Z-Axis high bytes 8
40 ACCEL_ZOUT_L Accelerometer Z-Axis low bytes 8

The I2C Slave Address will be 0x68 (https://learn.sparkfun.com/tutorials/mpu-9250-hookup-guide).

The following pseudocode demonstrates reading the values from the MPU-9520 sensor:

// Connect to camera
// Get device node map

// Turn on VoltageExternalEnable (GPIO VDD)
Set LineSelector = Line4;
VoltageTageExternalEnable = True;

I2CSlaveAddress = 0x68;
I2CSCLSource = Line2;
I2CSDASource = Line3;
I2CAccessLength = 1;                         // Read 1 byte at a time

// Set I2C Read Operation
I2COperationSelector = Read;

// Read ACCEL_XOUT_HIGH
I2CRegisterAddress = 0x3B;
I2COperationExecute();
// Confirm I2COperationStatus == Success
ACCEL_XOUT_HIGH = I2CAccessBuffer            // Read 1 byte out of I2CAccessBuffer

// Read ACCEL_XOUT_LOW
I2CRegisterAddress = 0x3C;
I2COperationExecute();
// Confirm I2COperationStatus == Success
ACCEL_XOUT_LOW = I2CAccessBuffer             // Read 1 byte out of I2CAccessBuffer

// Read ACCEL_YOUT_HIGH
I2CRegisterAddress = 0x3D;

I2COperationExecute();
// Confirm I2COperationStatus == Success
ACCEL_YOUT_HIGH = I2CAccessBuffer            // Read 1 byte out of I2CAccessBuffer

// Read ACCEL_YOUT_LOW
I2CRegisterAddress = 0x3E;
I2COperationExecute();
// Confirm I2COperationStatus == Success
ACCEL_YOUT_LOW = I2CAccessBuffer             // Read 1 byte out of I2CAccessBuffer

// Read ACCEL_ZOUT_HIGH
I2CRegisterAddress = 0x3F;
I2COperationExecute();
// Confirm I2COperationStatus == Success
ACCEL_ZOUT_HIGH = I2CAccessBuffer            // Read 1 byte out of I2CAccessBuffer

// Read ACCEL_ZOUT_LOW
I2CRegisterAddress = 0x40;
I2COperationExecute();
// Confirm I2COperationStatus == Success
ACCEL_ZOUT_LOW = I2CAccessBuffer             // Read 1 byte out of I2CAccessBuffer
Writing with I2C

The following registers will be read from the MPU-9250 sensor (https://www.invensense.com/download-pdf/mpu-9250-register-map/):

Address (Hex) Register Name Description Length (bits)
0D SELF_TEST_X_ACCEL Accelerometer X-Axis high bytes 8
0E SELF_TEST_Y_ACCEL Accelerometer X-Axis low bytes 8
0F SELF_TEST_Z_ACCEL Accelerometer Y-Axis high bytes 8

The I2C Slave Address will be 0x68 (https://learn.sparkfun.com/tutorials/mpu-9250-hookup-guide).

The following pseudocode demonstrates writing values to the MPU-9520 sensor:

// Connect to camera
// Get device node map

// Turn on VoltageExternalEnable (GPIO VDD)
Set LineSelector = Line4;
VoltageTageExternalEnable = True;

I2CSlaveAddress = 0x68;
I2CSCLSource = Line2;
I2CSDASource = Line3;
I2CAccessLength = 1;                        // Write 1 byte at a time

// Set I2C Write Operation
I2COperationSelector = Write

// Write 0x01 to SELF_TEST_X_ACCEL
I2CRegisterAddress = 0x0D;
I2CAccessBuffer = 0x01;
I2COperationExecute();
// Confirm I2COperationStatus == Success

// Write 0x01 to SELF_TEST_Y_ACCEL
I2CRegisterAddress = 0x0E;
I2CAccessBuffer = 0x01;
I2COperationExecute();
// Confirm I2COperationStatus == Success

// Write 0x01 to SELF_TEST_Z_ACCEL
I2CRegisterAddress = 0x0F;
I2CAccessBuffer = 0x01;
I2COperationExecute();
// Confirm I2COperationStatus == Success

// Read SELF_TEST_X_ACCEL

I2CRegisterAddress = 0x0D;
I2COperationExecute();
// Confirm I2COperationStatus == Success
SELF_TEST_X_ACCEL = I2CAccessBuffer            // Read 1 byte out of I2CAccessBuffer

// Read SELF_TEST_Y_ACCEL

I2CRegisterAddress = 0x0D;
I2COperationExecute();
// Confirm I2COperationStatus == Success
SELF_TEST_Y_ACCEL = I2CAccessBuffer            // Read 1 byte out of I2CAccessBuffer

// Read SELF_TEST_Z_ACCEL

I2CRegisterAddress = 0x0D;
I2COperationExecute();
// Confirm I2COperationStatus == Success
SELF_TEST_Z_ACCEL = I2CAccessBuffer            // Read 1 byte out of I2CAccessBuffer

See the following examples using Arena SDK for further demonstration:

  • Cpp_Camera_I2C_Read_Write, using Arena SDK for C++
  • py_camera_i2c_read_write, using Arena SDK for Python
Phoenix GPIO Characteristics
Phoenix camera GPIO

GPIO connector as seen from rear PHX050S view. Pin colors correspond to GPIO-8P20 cable from Lucid Vision Labs.

Pin Number Pin Description
1 (Red) VAUX (12-24V DC Power Input)
2 (Brown) Non-isolated bi-directional GPIO channel (Line 2)
3 (Orange) VDD GPIO (2.5V Power Output) (Line 4)
4 (Brown) Non-isolated bi-directional GPIO channel (Line 3)
5 (Black) GND (Camera GND)
6 (Blue) OPTO GND (Opto-isolated Reference)
7 (Yellow) OPTO OUT (Opto-isolated Output) (Line 1)
8 (Green) OPTO IN (Opto-isolated Input) (Line 0)


I2C Access Control Nodes

Node Name Description
I2COperationSelector Selects the target operation for the I2C communication on the device. This operation is executed when the I2COperationExecute feature is called.
I2COperationExecute Executes the operations selected by I2COperationSelector on the I2C communication.
I2CAccessBuffer Defines the intermediate access buffer that allows the exchange of data between the device’s I2C communication and the application.
I2CRegisterAddress Controls the register address for the operation selected by the I2COperationSelector.
I2CRegisterAddressLength Controls the register address length used for the I2C communication.
I2CAccessLength Controls the number of bytes to transfer to or from the I2CAccessBuffer.
I2COperationStatus Represents the I2COperationExecute status.
I2COperationResult Represents the number of successfully read/written bytes for the I2C operation.