Pmod COLOR Reference Manual

The Digilent Pmod COLOR (Revision A) is a color sensor module with the ability to sense red, green, blue and clear light. The onboard AMS TCS3472 integrates an IR blocking filter to accurately determine the color of objects as well as sense ambient light under varying lighting conditions and through attenuating materials.

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Features

  • Red, green, blue, and clear light sensing
  • IR-blocking filter
  • White LED for reflective measurements
  • Suitable for use behind darkened glass
  • Small PCB size for flexible designs 0.8“ × 1.25” (2.0 cm × 3.2 cm)
  • 6-pin Pmod connector with I²C interface
  • Pass-through Pmod host port for daisy chaining
  • Library and example code available on the Resource Center

Specifications

Parameter Min Typical Max Units
Power Supply Voltage 2.7 3 3.6 V
Parameter Channel Min Max Units
Responsivity to blue light (λ = 465 nm) Red Channel¹ 0% 15% counts/μW/cm²
Green Channel¹ 10% 42% counts/μW/cm²
Blue Channel¹ 65% 88% counts/μW/cm²
Clear Channel 11.0 16.6 counts/μW/cm²
Responsivity to green light (λ = 525 nm) Red Channel¹ 4% 25% counts/μW/cm²
Green Channel¹ 60% 85% counts/μW/cm²
Blue Channel¹ 10% 45% counts/μW/cm²
Clear Channel 13.2 20.0 counts/μW/cm²
Responsivity to red light (λ = 615 nm) Red Channel¹ 80% 110% counts/μW/cm²
Green Channel¹ 0% 14% counts/μW/cm²
Blue Channel¹ 5% 24% counts/μW/cm²
Clear Channel 15.6 23.4 counts/μW/cm²
Parameter Value Units
Output Resolution 16 bits

¹ - Percent values are with respect to the counts measured by the clear (non-color filtered) channel


Pinout Table Diagram

Header J1 Header J2 Jumper JP1
Pin Signal Description Pin Signal Description Pin Status Description
1 IO1/~INT I/O pin 1 or active low interrupt 1 IO1/~INT I/O pin 1 or active low interrupt SCL Loaded/ Unloaded 2.2 kΩ Pullup to Vcc/No Pullup to Vcc
2 IO2/LED_EN I/O pin 2 or LED enable 2 IO2/LED_EN I/O pin 2 or LED enable Jumper JP2
3 SCL Serial Clock 3 SCL Serial Clock SDA Loaded/ Unloaded 2.2 kΩ Pullup to Vcc/No Pullup to Vcc
4 SDA Serial Data 4 SDA Serial Data Jumper JP3
5 GND Power Supply Ground 5 GND Power Supply Ground ~INT Loaded/ Unloaded Enable/Disable the active low interrupt
6 VCC Power Supply (3.3V) 6 VCC Power Supply (3.3V) Jumper JP4
LED_EN Loaded/ Unloaded Enable/Disable the LED enable pin

Physical Dimensions

The pins on the pin header are spaced 100 mil apart. The PCB is 1.34 inches long on the sides parallel to the pins on the pin header and 0.8 inches long on the sides perpendicular to the pin header.


Functional Description

The Pmod Color utilizes the TCS3472 to detect color in the near vicinity. While communicating with the host board via the I²C protocol using an I²C address of 0x29 users can measure color. A user controlled white LED is also provided to help illuminate the object and improve color determination; the LED is very bright so it is recommended that users do not stare at the light.

Serial Communication

The Pmod COLOR communicates with the host board via the I²C protocol. By first sending the 7-bit I²C device address of 0101001 (0x29), users may receive the color data from the TCS3472. Each of the four ADC channels (red, green, blue, and clear) sends it's conversion from the ADC to the host buffer simultaneously.

The TCS3472 can set the gain and integration time for each round of data collection. Integration time provides more time for the color sensor to collect more data, providing accurate data and helping to prevent the data from disproportionately capturing any overexposure that may occur. Each set of the 16-bit data is organized in a low-byte, high-byte arrangement.

Register Details

Data Registers

Each of the three colors (RGB) and the clear color byte has two registers to store the high and low data bytes for each measurement. The data registers are arranged in a low byte, high byte arrangement.

Data Registers addresses 0x14 to 0x1B
Address Register Name
0x14 Clear Data Low Byte
0x15 Clear Data High Byte
0x16 Red Data Low Byte
0x17 Red Data High Byte
0x18 Green Data Low Byte
0x19 Green Data High Byte
0x1A Blue Data Low Byte
0x1B Blue Data High Byte

Command Register

The Command register controls the functionality of the internal address pointer and clears interrupts.

Bit Name Bit Number Bit Description Bit Values Functional Description
CMD 7 Command Select the command register; must be set high
TYPE 6-5 Type 00¹ Selects the type of data transfer²
ADDR/SF 4-0 Address/Special Field 00000¹ Register address field and special function field³

¹ - This is the value on power-up and reset ² - See the Transaction Table below ³ - See the Address Field and Special Function Table below

Transaction Table

Transaction Table
Bit Values Transaction Type
00 Repeated bytes at the same register
01 Auto-increment to the next register
10 Reserved - Do not write
11 Special function³

³ - See the Address Field and Special Function Table below

Address Field and Special Function Table

Address Field and Special Function Field
Bit Values Read Value
00110 Clears any pending interrupts and self clears
Other Reserved - Do not write

Control Register (0x0F)

The Control Register (0x0F) sets the gain factor applied to the ADC color data.

Control Register
Bit Name Bit Number Bit Description Bit Values Functional Description
Reserved 7-2 Reserved 000000¹ Reserved - Write as 0
AGAIN 1-0 Analog gain 00¹ RGBC Gain Control²

¹ - This is the value on power-up and reset ² - See the Gain Value Table below

RGBC Gain Value Table

RGBC Gain Value Table
Bit Value RGBC Gain Value
00 1x gain
01 4x gain
10 16x gain
11 60x gain

Status Register (0x13)

The Status register (0x13) is a read-only register that provides the state of the channel interrupt and if the ADCs have completed a data collection.

Status Register
Bit Name Bit Number Bit Description Bit Values Functional Description
Reserved 7-5 Reserved 000¹ Reserved
AINT 4 Analog Data Interrupt RGBC clear channel interrupt
Reserved 3-1 Reserved 000¹ Reserved
AVALID 0 Analog Data Valid RGBC valid bit when the channels have completed an integration cycle

¹ - This is the value on power-up and reset

Quick Start

Here is the series of commands to acquire a set of data from the Pmod COLOR via pseudo I²C code.

  1. Power on the Pmod COLOR.
  2. Provide a START condition and call the device ID with a write bit
    I2CBegin(0x52); //device ID 0x29 with a write (0) bit
  3. Wait to receive an ACK from the Pmod COLOR.
  4. Provide a command to maintain the pointer address OR'd with the Enable register (0x00)
    I2CWrite(0xA0); //Maintain the pointer address at the Enable register
  5. Wait to receive an ACK from the Pmod COLOR.
  6. Send the Enable Address and enable the oscillators.
    I2CWrite(0x01); //0x01 enables the oscillators for the timers and ADC channels
  7. Delay at least 2.4 mS before starting a data collection initiation.
  8. Send the Enable Address and enable the ADCs for all 4 channels.
    I2CWrite(0x02); //0x02 enables the ADC channels
  9. Wait to receive an ACK from the Pmod COLOR and then send a STOP condition.
  10. Delay 2.4 ms for the ADCs preparing themselves for data measurement and at least 2.4 ms by default for the integration time during the data collection process.
  11. Send a START condition and call the device ID with a write bit
    I2CBegin(0x52); //device ID 0x29 with a write (0) bit
  12. Wait to receive an ACK from the Pmod COLOR.
  13. Provide a command to auto-increment the address pointer OR'd with the first data register (0x14)
    I2CWrite(0xB4); //Auto-increment the pointer address starting at the Clear Data Low Byte register
  14. Wait to receive an ACK from the Pmod COLOR
  15. Provide a RESTART condition and call the device ID with a read bit
    I2CBegin(0x53); //device ID 0x29 with a read (1) bit
  16. Wait to receive an ACK from the Pmod COLOR.
  17. Collect all 8 data bytes corresponding to the low and high data byte registers of the clear, red, green, and blue data, respectively, sending an ACK to the Pmod Color between each byte.
    I2CReadMultiple(8); //read in the 8 data registers taking advantage of the auto-incrementing pointer
  18. Send a STOP condition.

Applications Information

The Pmod COLOR is ideal for fun applications that perform different tasks based on the color of an object. This is perfect for sorting different objects or controlling a motor based on the detected color temperature.

Data Conversion

The AMS TCS3472 module has four different ADC channels to detect red, green, blue, and clear ambient light data. Colorimeters of this nature do not have perfect sensing capability so some of the color sensors, notably green and blue, do not measure the full data range of the data

Timing Diagrams

An example timing diagram for reading and writing to the Pmod COLOR taken from the AMS datasheet is provided below:

Pmod COLOR Timing Diagram

When using an external power supply to run the Pmod, be sure to stay within the parameters provided in Specifications.


Additional Information

The schematics of the Pmod COLOR are available here. Additional information about the color sensor including communication modes and specific timings of the chip can be found by downloading its datasheet from the AMS website here here.

Example code demonstrating how to get information from the Pmod COLOR can be found on its Resource Center here.

If you have any questions or comments about the Pmod COLOR, feel free to post them under the appropriate section (“Add-on Boards”) of the Digilent Forum.