PmodALS Reference Manual

的DigilentPmodALS(Revision A) demonstrates light-to-digital sensing through a single ambient light sensor. Digilent Engineers designed this Pmod around theTexas Instruments ADC081S021analog-to-digital converter andVishay Semiconductor's TEMT6000X01.

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• Simple ambient light sensor
• Convert light to digital data with 8-bit resolution
• 6-pin Pmod端口和SPI interface

The PmodALS utilizes a single ambient light sensor (ALS) for user input. The amount of light the ALS is exposed to determines the voltage level passed into theADC, which converts it to 8-bits of data. A value of 0 indicates a low light level and a value of 255 indicates a high light level.

The PmodALS communicates with the host board via theSPI protocolin SPI Mode 3. Since the on-board analog-to-digital converter is a read-only module, the only wires in the SPI protocol that are required are the Chip Select, Master-In-Slave-Out, and Serial Clock lines. The location of each of these lines on the Pmod header are shown in the table below.

Table 1Connector J1- Pin Descriptions as labeled on the Pmod

The PmodALS reports to the host board when the ADC081S021 is placed in normal mode by bringing theCSpin low, and delivers a single reading in 16SCLKclock cycles. The PmodALS requires the frequency of theSCLKto be between 1MHzand 4 MHz. The bits of information, placed on the falling edge of theSCLKand valid on the subsequent rising edge ofSCLK, consist of three leading zeroes, the eight bits of information with the MSB first, and four trailing zeroes. An occasional 4th leading zero may be captured ifCSgoes low to initiate another data transfer before the rising edgeSCLK.

Any external power applied to the PmodALS must be within 2.7V and 5.25V; however, it is recommended that Pmod is operated at 3.3V.

The pins on the pin header are spaced 100 mil apart. The PCB is 0.8 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.

The schematics of the PmodALS are availablehere. Additional information about the ADC including communication modes and specific timings of the chip can be found by checking out its datasheethere. Similarly, the datasheet for the ambient light sensor can be foundhere.

More specific information about how to use the PmodALS can be found by checking out ouruser guide. Example code demonstrating how to get information from the PmodALS can be foundhere.

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