SBAA565 November   2022 ADC081C021 , ADC081C027 , ADC101C021 , ADC101C027 , ADC121C021 , ADC121C021-Q1 , ADC121C027 , ADC128D818 , ADS1000 , ADS1000-Q1 , ADS1013 , ADS1014 , ADS1015 , ADS1015-Q1 , ADS1100 , ADS1110 , ADS1112 , ADS1113 , ADS1114 , ADS1115 , ADS1115-Q1 , ADS7823 , ADS7827 , ADS7828 , ADS7828-Q1 , ADS7830 , ADS7924 , AFE539A4 , DAC081C081 , DAC081C085 , DAC101C081 , DAC101C081Q , DAC101C085 , DAC121C081 , DAC121C085 , DAC43204 , DAC43401 , DAC43401-Q1 , DAC43608 , DAC43701 , DAC43701-Q1 , DAC53002 , DAC53004 , DAC53202 , DAC53204 , DAC53204W , DAC53401 , DAC53401-Q1 , DAC53608 , DAC53701 , DAC53701-Q1 , DAC5571 , DAC5573 , DAC5574 , DAC5578 , DAC60501 , DAC60502 , DAC63002 , DAC63004 , DAC63202 , DAC63204 , DAC6571 , DAC6573 , DAC6574 , DAC6578 , DAC70501 , DAC70502 , DAC7571 , DAC7573 , DAC7574 , DAC7578 , DAC7678 , DAC80501 , DAC80502 , DAC8571 , DAC8574

 

  1.   Abstract
  2.   Trademarks
  3. 1I2C Overview
    1. 1.1 History
    2. 1.2 I2C Speed Modes
  4. 2I2C Physical Layer
    1. 2.1 Two-Wire Communication
    2. 2.2 Open-Drain Connection
    3. 2.3 Non-Destructive Bus Contention
  5. 3I2C Protocol
    1. 3.1 I2C START and STOP
    2. 3.2 Logical Ones and Zeros
    3. 3.3 I2C Communication Frames
  6. 4I2C Examples
    1. 4.1 DAC80501 Example
      1. 4.1.1 DAC80501 DAC Data Register
      2. 4.1.2 DAC80501 I2C Example Write
    2. 4.2 ADS1115 Example
      1. 4.2.1 ADS1115 Configuration Register
      2. 4.2.2 ADS1115 I2C Example Read
      3. 4.2.3 ADS1115 Conversion Result
  7. 5Reserved Addresses
    1. 5.1 General Call
    2. 5.2 START Byte
    3. 5.3 C-Bus Address, Different Bus Format, Future Purposes
    4. 5.4 HS-Mode Controller Code
    5. 5.5 Device ID
    6. 5.6 10-Bit Target Addressing
      1. 5.6.1 10-Bit Target Addressing Write
      2. 5.6.2 10-Bit Target Addressing Read
  8. 6Advanced Topics
    1. 6.1 Clock Synchronization and Arbitration
    2. 6.2 Clock Stretching
    3. 6.3 Electrical Specifications
    4. 6.4 Voltage Level Translation
      1. 6.4.1 Example 1
      2. 6.4.2 Example 2
      3. 6.4.3 Example 3
      4. 6.4.4 Example 4
    5. 6.5 Pullup Resistor Sizing
      1. 6.5.1 Minimum Pullup Resistance Sizing
      2. 6.5.2 Maximum Pullup Resistance Sizing
  9. 7Protocols Similar to I2C
  10. 8Summary

4.2 ADS1115 Example

In this second example, I2C is used to read data from a precision ADC. The ADS1115 is a 16-bit precision ADC that uses an I2C interface and is capable of standard, fast, and high-speed modes. The device has several settings that can be set through a configuration register, including the input range set by a programmable gain amplifier (or PGA), a variety of data rates, and an input multiplexer that can be set to make differential measurements, or single-ended measurements with respect to ground. Figure 4-3 shows the functional block diagram for the ADS1115.

Figure 4-3 ADS1115 Functional Block Diagram

Similar to the previous example, the ADS1115 has an address pin labeled ADDR. This pin is used to select one of four I2C addresses, meaning that four of these devices can be used on the same bus as long as the devices are programmed to different addresses. The I2C address used for the device depends on the ADDR pin connection. With the ADDR pin connected to VDD, SDA, or SCL, the device can be set to other addresses shown in the table. For this example, the ADDR set to ground, so the address is set to 48h.

The ADS1115 has four internal registers, each addressed by an internal pointer register. The first register is the conversion data register. When the ADC completes a conversion, the ADC data is placed in this register and the controller device reads this register.

The second register is the configuration register. The controller device writes to this register to program the device and start a conversion. The configuration register sets the programmable gain amplifier, the input channel, the data rate, and other modes of operation for the device.

The last two registers are the Lo_threshold register and the Hi_threshold register. These two registers are used to set thresholds for a digital comparator in the device. Once the conversion data goes beyond these thresholds, the device can set an alert to the ALERT/RDY pin. For this example, the comparator and the thresholds are not configured.

For this example, the settings for the configuration register are first shown to explain the settings and range of the ADC. After that, an example I2C read from conversion register for the ADC is shown.