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The Serial Interface
3-3
Usage
3.2
The Serial Interface
The ADS1244/45 serial interface is connected directly to the
ADS1244/45EVM serial connector. Therefore, the way you connect the
ADS1244/45EVM in a prototype situation can be the same as the way you
connect it in your final product. This discussion assumes that you will be
connecting the ADS1244/45EVM to a microcontroller, but for FPGA and
PC−based systems, similar principles apply.
There are two primary ways to connect the ADS1244/45. If you are using
GPIO (“bit−banging”) to communicate with the device, you can use only the
serial data / data ready line (J5 pin 13) and the serial clock line (J5 pin 3).
By polling the data line, you can determine when the ADS1244/45 has a
new code ready. You might also let the data line interrupt the processor, if
your processor supports this.
If the microcontroller has an SPI peripheral, you can also use this, together
with an interrupt input, to read from the ADS1244/45. This is done by con-
necting the serial data line to both SDI / MOSI on the microcontroller and
also to the interrupt input.
The ADS1244/45EVM is pre−wired for this method. The standard serial
connector has an interrupt output pin (J5 pin 15). The data line is wired to
both this pin and the serial data pin.
Of course, you can still use the bit−bang method to communicate with the
ADS1244/45. Simply ignore the interrupt output pin and use GPIO instead
of a dedicated SPI peripheral.
3.3
The Serial EEPROM
The serial EEPROM is a Microchip 24LC256 32KB type. You can use it in
any way you need to; the chip is not programmed during manufacturing.
Possible uses include calibration data or board ID information.
Information on communicating with the EEPROM is available from Micro-
chip Technology, Inc.