Holt Integrated Circuits
11
Now decrease the voltage, LED1 and S01 should go off before 6V is reached and the screen
should go back to reading 0000.
5.
An individual sensor can also be monitored from the INTB output to provide a hardware
trigger, connect an oscilloscope probe to the INTB test point. Use this output as a trigger to
an oscilloscope, input a ramp voltage to the sensor and monitor the ramp on another
channel of the oscilloscope. When the sensor changes the INTB signal triggers the
oscilloscope the negative edge of INTB will cross the ramp at the threshold point, allowing
easy measurement.
Daisy Chained SPI Mode
1.
Two HI-8400 boards are provided with the evaluation kit. Board 1 is the master board with a
microprocessor to control the interface. Board2 is used for daisy chain testing and should be
plugged into Board1 at connector J7. The console option ‘m’, continually reads the SPI data
from both devices in the daisy chain configuration. To get active sensor data, the sensors on
board2 will need to be connected to a 28V supply and sensor voltage. Connector J7 links the
SPI connections of the two devices; the SO pin of Board1 is linked to the SI pin of Board2. The
software has commands that read both devices through the SO pin of Board2.
