Pmod R2R Reference Manual
The Digilent Pmod R2R (Revision B) is an 8-bit Digital-to-Analog converter. It may not look as sleek and professional as some of the other DACs that are out there, but on a fundamental level that is easy to see, this Pmod does exactly the same thing as its counterparts.
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- 8-bit digital-to-analog conversion
- Convert data at up to 25MHz
- Easy attachment of oscilloscopes to illustrate the data conversion process
- 2×6-pin Pmod port with GPIO interface
The Pmod R2R accepts 8 bits in parallel, either at a logic low or high voltage, which then go through a resistor ladder to output a desired voltage. The “R2R” resistor ladder is one of the most popular ways that digital-to-analog converters take a set of digital inputs and create a single analog output, requiring just two resistor values of R and 2*R. Because this Pmod only uses 10K Ω and 20K Ω resistors, very little current is drawn from the input pins.
Interfacing with the Pmod
The Pmod R2R communicates with the host board via the GPIO protocol. Each of the 8 input pins are expected to send out either a logic high or logic low voltage signal in such a way that represents the desired binary ratio of the full analog output.
Pinout Description Table
|Pin Number (top row)||Description||Pin Number (bottom row)||Description|
|1||Data Bit 0||7||Data Bit 4|
|2||Data Bit 1||8||Data Bit 5|
|3||Data Bit 2||9||Data Bit 6|
|4||Data Bit 3||10||Data Bit 7|
The pins on the pin header are spaced 100 mil apart. The PCB is 1 inch 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.