ADS1015 datasheet(21/33 Pages) TI1

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VDD

GPIO_0

GPIO_1

Microcontrolleror

Microprocessor

withGPIOPorts

ADDR

ALERT/RDY

GND

AIN0

AIN1

SCL

SDA

VDD

AIN3

AIN2

ADS1015

ADS1013

ADS1014

ADS1015

www.ti.com

SBAS473C – MAY 2009 – REVISED OCTOBER 2009

CONNECTING MULTIPLE DEVICES

states. To drive the line low, the pin is set to output

'0'; to let the line go high, the pin is set to input. When

Connecting multiple ADS1013/4/5s to a single bus is

the pin is set to input, the state of the pin can be

simple. Using the address pin, the ADS1013/4/5 can

read; if another device is pulling the line low, this

be set to one of four different I2C addresses. An

configuration reads as a '0' in the port input register.

example showing four ADS1013/4/5 devices is given

in Figure 21. Up to four ADS1013/4/5s (using

Note that no pull-up resistor is shown on the SCL

different

address

configurations)

can

line. In this simple case, the resistor is not needed;

connected to a single bus.

the microcontroller can simply leave the line on

output, and set it to '1' or '0' as appropriate. This

Note that only one set of pull-up resistors is needed

action is possible because the ADS1013/4/5 never

per bus. The pull-up resistor values may need to be

drive the clock line low. This technique can also be

lowered slightly to compensate for the additional bus

used with multiple devices, and has the advantage of

capacitance

presented

multiple

devices

and

lower current consumption as a result of the absence

increased line length.

of a resistive pull-up.

The TMP421 and DAC8574 devices detect the

If there are any devices on the bus that may drive the

respective I2C bus addresses based on the states of

clock lines low, this method should not be used; the

pins. In Figure 22, the TMP421 has the address

SCL line should be high-Z or '0' and a pull-up resistor

0101010,

and

the

DAC8574

has

the

address

provided as usual.

1001100. Consult the DAC8574 and TMP421 data

sheets, available at www.ti.com, for further details.

Some microcontrollers have selectable strong pull-up

circuits built in to the GPIO ports. In some cases,

these circuits can be switched on and used in place

USING GPIO PORTS FOR COMMUNICATION

of an external pull-up resistor. Weak pull-ups are also

Most

microcontrollers

have

programmable

provided on some microcontrollers, but usually these

input/output (I/O) pins that can be set in software to

are too weak for I2C communication. If there is any

act as inputs or outputs. If an I2C controller is not

doubt about the matter, test the circuit before

available, the ADS1013/4/5 can be connected to

committing it to production.

GPIO pins and the I2C bus protocol simulated, or

bit-banged,

software.

example

this

configuration for a single ADS1013/4/5 is shown in

Figure 20.

Bit-banging I2C with GPIO pins can be done by

setting the GPIO line to '0' and toggling it between

input and output modes to apply the proper bus

NOTE: ADS1013/4/5 power and input connections omitted for clarity.

Figure 20. Using GPIO with a Single ADS1015

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Product Folder Link(s): ADS1013 ADS1014 ADS1015

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