PMODIA_RM Datasheet, PDF (1/3 Pages) List of Unclassifed Manufacturers – Digilent PmodIA™ Impedance Analyzer Reference Manual

Digilent PmodIA™ Impedance
Analyzer Reference Manual
Revision: November 01, 2012
Note: This document applies to REV A of the board
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Overview
The PmodIA is an impedance analyzer built
around the Analog Devices AD5933
Impedance Converter Network Analyzer.
Features include:
• I²C communication interface
• capable of measuring impedances
ranging from 100Ω to 10 MΩ.
• programmable frequency sweep: start
frequency, step increment, and number
of steps.
• programmable gain amplifier
• external clock generation optional
Functional Description
The PmodIA uses an 8-pin connector that
allows for I²C communication. There is also a
1-pin connector that allows you to select either
a high or low impedance measurement.
The PmodIA measures impedance by emitting
an AC voltage at a known frequency and
sampling the frequency response to identify
the unknown impedance value. You can
access the voltage output via the SMA
connector J3. SMA connector J4 captures the
response.
Please see the AD5933 data sheet, available
from www.analog.com, for more detailed
information on controlling the analyzer.
I²C Interface
The PmodIA acts as a slave device using I²C
communication protocol. The I²C interface
standard uses two signal lines. These are I²C
data and I²C 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 it’s 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.
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