Preliminary Technical Data
Rev. PrA | Page 9 of 20
The ADIS16385 is an autonomous system that requires no user
initialization. When it has a valid power supply, it initializes
itself and starts sampling, processing, and loading sensor data
into the output registers at a sample rate of 1024 SPS. DIO1
pulses high after each sample cycle concludes. The SPI interface
enables simple integration with many embedded processor
platforms, as shown in Figure 10 (electrical connection) and
Table 6 (pin descriptions).
I/O LINES ARE COMPATIBLE WITH
3.3V OR 5V LOGIC LEVELS
Figure 10. Electrical Connection Diagram
Table 6. Generic Master Processor Pin Names and Functions
Master output, slave input
Master input, slave output
The ADIS16385 SPI interface supports full duplex serial
communication (simultaneous transmit and receive) and uses
the bit sequence shown in Figure 14. Table 7 provides a list of
the most common settings that require attention to initialize a
processor’s serial port for the ADIS16385 SPI interface.
Table 7. Generic Master Processor SPI Settings
The ADIS16385 operates as a slave
SCLK Rate ≤ 2 MHz1
Maximum serial clock rate
SPI Mode 3
CPOL = 1 (polarity), CPHA = 1 (phase)
MSB First Mode
Shift register/data length
1 For burst read, SCLK rate ≤ 1 MHz. For low power mode, SCLK rate ≤ 300 kHz.
READING SENSOR DATA
The ADIS16385 provides two different options for acquiring
sensor data: single register and burst register. A single register
read requires two 16-bit SPI cycles. The first cycle requests the
contents of a register using the bit assignments in Figure 14.
Bit DC7 to Bit DC0 are don’t care for a read, and then the output
register contents follow on DOUT during the second sequence.
Figure 11 includes three single register reads in succession. In
this example, the process starts with DIN = 0x0400 to request
the contents of XGYRO_OUT, and follows with 0x0600 to
request YGYRO_OUT, and 0x0800 to request ZGYRO_OUT.
Full duplex operation enables processors to use the same 16-bit
SPI cycle to read data from DOUT while requesting the next set
of data on DIN. Figure 12 provides an example of the four SPI
signals when reading XGYRO_OUT in a repeating pattern.
Figure 11. SPI Read Example
Figure 12. Example SPI Read, Second 16-Bit Sequence
The burst-read function enables the user to read all output registers
using one command on the DIN line and shortens the stall time
between each 16-bit segment to 1 SCLK cycle (see Table 2).
Figure 13 provides the burst-read sequence of data on each SPI
signal. The sequence starts with writing 0x3E00 to DIN, followed
by each output register clocking out on DOUT, in the order in
which they appear in Table 8.
Figure 13. Burst-Read Sequence
1. DOUT BITS ARE PRODUCED ONLY WHEN THE PREVIOUS 16-BIT DIN SEQUENCE STARTS WITH R/W = 0.
Figure 14. SPI Communication Bit Sequence