====== 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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== Download This Reference Manual ==
  * {{:reference:pmod:pmodr2r:pmodr2r_rm.pdf| PDF}}

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===== Features =====
  * 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

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=====Functional Description =====
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.

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===== Interfacing with the Pmod=====
The %%Pmod R2R%% communicates with the host board via the [[pmod:communication_protocols:gpio|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 ====
^  Header J1  |||||
^  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  |
|  5  |  Ground                          |:::|  11  |  Ground  |
|  6  |  VCC                             |:::|  12  |  VCC  |


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===== Physical Dimensions =====
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.
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===== Additional Information =====
The schematics of the %%Pmod R2R%% are available {{reference:pmod:pmodr2r:pmodr2r_sch.pdf|here}}.

Example code demonstrating how to get information from the %%Pmod R2R%% can be found [[pmod:pmodr2r:start#example_projects|here]]. 

If you have any questions or comments about the %%Pmod R2R%%, feel free to post them under the appropriate section ("Add-on Boards") of the [[https://forum.digilent.com/|Digilent Forum]].