410-246 Digilent

1300 Henley Court Pullman, WA 99163 509.334.6306 www.digilentinc.com PmodIA Reference Manual Revised April 15, 2016 This manual applies to the PmodIA rev. A Overview The PmodIA is an impedance analyzer built around the Analog Devices AD5933 12-bit Impedance Converter Network Analyzer. Features include: Impedance analyzer with 12-bit impedance converter Measure impedance values ranging from 100 to 10 M. Programmable frequency sweep Programmable gain amplifier Optional external clock generation Small PCB size for flexible designs 1.6 in 0.8 in (4.1 cm 2.0 cm) 24-pin port with IC interface Follows Digilent Interface Specification Library and example code available in resource center The PmodIA. 1 Functional Description The PmodIA utilizes Analog Devices AD5933 with its on-board frequency generator and analog-to-digital converter (ADC) to be able to excite an external unknown impedance at a known frequency. This known frequency is sent out through one of the SMA connectors. The frequency response is captured by the other SMA connector and sent to the ADC and a discrete Fourier transform (DFT) is performed on sampled data, storing the real and imaginary parts of the solution in the on-chip data registers. The magnitude of the unknown impedance as well as the relative phase of the impedance at each point in the generated frequency sweep can be calculated from these two data words. Copyright Digilent, Inc. All rights reserved. DOC : 502-246 Page 1 of 5 Other product and company names mentioned may be trademarks of their respective owners. PmodIA Reference Manual 2 1.1 I C Interface 2 2 The PmodIA acts as a slave device using I C communication protocol. The I C interface standard uses two signal 2 2 lines. These are I C data and I C clock. These signals map to the serial data (SDA) and serial clock (SCL) respectively on the PmodIA. (See Table 1.) The following instructions explain how to read and write to the device. You must consider two protocols when writing to the PmodIA: the write byte/command byte and the block write. Writing a single byte from the master to the slave requires the master to initiate a start condition and send the 7- bit slave address. You must hold the read/write bit low to write to the slave device successfully. The PmodIA should set the slave address as 0001101 (0x0D) upon startup. After the slave acknowledges its address, the master must send the address of the register it wants to write to. Once the slave acknowledges receipt of this address, the master will send a single data byte that the slave should acknowledge with a return bit. The master should then issue a stop condition. You can also use this protocol to set a pointer for a register address. After the master sends the slave address and write bit, and the slave responds with an acknowledge bit, the master sends a pointer command byte (10110000, or, 0xB0). The slave will assert an acknowledge bit and then the master will send the address of the register to point to in memory. The next time the device reads from or writes data to a register, it will occur at this address. Note: The pointer must be set prior to using block write or block read protocols. You can perform a block write protocol in a similar fashion to setting a pointer. Send the block write command (10100000, or, 0xA0) in place of the pointer command, and the number of bytes being sent (represented as a byte) will take the place of the register address with subsequent data bytes being zero indexed. Use the same two protocols when reading data from the PmodIA: receive byte and block read. 2 Connector J1 I C Communications Pin Signal Description 2 1, 2 SCL I C clock 2 3, 4 SDA I C data 5, 6 GND Power supply Ground 7, 8 VCC Power supply (3.3V/5V) Table 1. Interface Connector Signal Description 1.2 Clock Source The PmodIA has an internal oscillator that generates a 16.776 MHz clock to run the device. You can use an external clock by loading IC4 on the PmodIA and setting bit 3 in the control register (register address 0x80 and 0x81). The PmodIA schematic provides a list of recommended oscillators. The schematic is available from the PmodIA product page at www.digilentinc.com. Copyright Digilent, Inc. All rights reserved. Page 2 of 5 Other product and company names mentioned may be trademarks of their respective owners.