• ADN2850

• EVAL-ADN2850SDZ

This document presents the steps to setup an environment for using the EVAL-ADN2850SDZ evaluation board together with the Xilinx KC705 FPGA board, the Xilinx Embedded Development Kit (EDK) and the Micrium µC-Probe run-time monitoring tool. Below is presented a picture of the EVAL-ADN2850SDZ Evaluation Board with the Xilinx KC705 board.

Below is presented a picture of SDP-B Controller Board with the EVAL-ADN2850SDZ Evaluation Board.

The ADN2850 is a dual-channel, nonvolatile memory, digitally controlled resistors with 1024-step resolution, offering guaranteed maximum low resistor tolerance error of ±8%. The device performs the same electronic adjustment function as a mechanical rheostat with enhanced resolution, solid state reliability, and superior low temperature coefficient performance. The versatile programming of the ADN2850 via an SPI®-compatible serial interface allows 16 modes of operation and adjustment including scratchpad programming, memory storing and restoring, increment/decrement, ±6 dB/step log taper adjustment, wiper setting readback, and extra EEMEM for user-defined information such as memory data for other components, look-up table, or system identification information.

The EVAL-ADN2850SDZ evaluation board is a member of a growing number of boards available for the SDP. Designed to help customers evaluate performance or quickly prototype new ADN2850 circuits and reduce design time, the EVAL-ADN2850SDZ evaluation board can operate in single-supply and dual-supply mode and incorporates an internal power supply powered from the USB.

• ADN2850 Product Info - pricing, samples, datasheet
• EVAL-ADN2850SDZ evaluation board user guide
• Xilinx KC705 FPGA board
• Micrium uC-Probe

The first objective is to ensure that you have all of the items needed and to install the software tools so that you are ready to create and run the evaluation project.

• Xilinx KC705 FPGA board
• FMC-SDP adapter board
• EVAL-ADN2850 evaluation board

• Xilinx ISE 13.4 (Programmer (IMPACT) is sufficient for the demo and is available on Webpack).
• uC-Probe run-time monitoring tool

• Reference Design Files

The following table presents a short description the reference design archive contents.

The following figure presents the uC-Probe interface that can be used for monitoring and controlling the operation of the EVAL-ADN2850SDZ evaluation board.

Section A is used to activate the board and monitor activity. The communication with the board is activated / deactivated by toggling the ON/OFF switch. The Activity LED turns green when the communication is active. If the ON/OFF switch is set to ON and the Activity LED is BLACK it means that there is a communication problem with the board. See the Troubleshooting section for indications on how to fix the communication problems.

Section B is used to send commands specific for the two RDAC channels available in the ADn2850. Toggling to On the switches under a specific RDAC will send the command only to that RDAC. The following commands can be sent to the two RDAC channels individually:

• +6dB - increments the RDAC value by 6dB
• -6dB - decrements the RDAC value by 6dB
• +1 Step - increments the RDAC value by 1
• -1 Step - decrements the RDAC value by 1
• Store – stores the value of the RDAC into the corresponding EEPROM
• Restore – restores into the RDAC the value from the corresponding EEPROM
• Write – writes into the RDAC the value selected in Section D by the slider Value for RDAC write

Below the individual command options there is a set of generic switches which are used to send commands to both RDACs simultaneously. The following commands can be sent simultaneously to both RDACs:

• +1 Step - increments the RDACs values by 1
• -1 Step - decrements the RDACs values by 1
• +6dB - increments the RDACs values by 6dB
• -6dB - decrements the RDACs values by 6dB
• Reset - resets the values stored in both RDACs to 0

Section C is used to send generic commands to the ADn2850. The command list is available in table 8 from the ADn2850 datasheet, page 16 (AD5235 Rev. D). The request values will be updated based on the switch selections and displayed in the Request numeric boxes. The command is sent by toggling the Send Command switch to On. After the command a NOP will be sent on and the values from the SDO will be displayed in the Response numeric boxes.

Section D is used for setting the values for Write requests both for RDAC wiper writes and memory writes. In case of RDAC writes, the Address value is not used. In case of memory writes, the Address value is used to select the memory location. It is recommended to use the first slider for values that are stored in user memory locations and the second slider for values that are written in the RDAC wiper or RDAC memory location EEMEM0 and EEMEM1.

Section E is used to toggle the hardware pins. The functionality of the pins is described in the ADn2850 datasheet, Table 4 at page 8. When the Write Protect switch is sent to On it isn’t possible to write to the memory nor change the RDAC values. Exceptions are the Restore/Reset function and toggling the \PR switch. In all cases the RDACs wipers will be reloaded with the values from the memory.

Section F displays the values stored in the EEPROM memories and the tolerance value. The displayed values are updated by toggling the Read switch to On. The Write switch controls the writing of the value specified by the slider Value for User Write to the memory address specified by the slider Address for EEMEM Write from Section D.

In case there is a communication problem with the board the follwing actions can be perfomed in order to try to fix the issues:

• Check that the evaluation board is powered as instructed in the board's user guide.
• In uC-Probe refresh the symbols file by right-clicking on the System Browser window and selecting Refresh Symbols.
• If the communication problem persists even after performing the previous steps, restart the uC-Probe application and try to run the interface again.

• ADN2850 Digital Potentiometer Linux Driver