AD7730 Serial Communication

Brian Smith

AD7730 Serial Communication

Ive made a force transducer (threaded tube with 4 strain gauges) and am trying to measure strain using the AD7730 ADC.
DATA SHEET-·· http://www.futurlec.com/AnalogDevices/AD7730BN.shtml

I have the DC bridge circuit connected as shown on p25 of this·link. http://www.futurlec.com/AnalogDevices/AD7730BNa.shtml

I have been reading the data sheet, but it only confuses me more. What do I need to do to recieve the serial data from this chip? What determines baud rate? If anyone has code for the basic stamp or Propeller that would really help me out.

deSilva

The chip sports a very simple serial interface, for reasons unknown sometimes refered to as "SPI" The data sheet says you have to clock it between 1 and 5 MHz.

You send instructions to the chip, as explained in figure 4 and table V.
It is very similar as if you are using a kind of 2x16 display, in serial mode (when they have it!) or in 4-bit mode.

But I see this is not an easy chip....

Paul Baker

Hi Brian, as deSilva has mentioned the chip is a synchronous serial interface (commonly refered to as SPI), the clock signal (SCLK) determines the data rate. Figures 18 and 19 show the timing diagram for the serial communication. You may be able to use the Propeller Object for the ADS7822P as a starting point to write your own object for the AD7730, though I haven't done much comparison to see how similar they are,·at the very least you shouild be able to use the SPI code.

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Paul Baker
Propeller Applications Engineer

Parallax, Inc.