An initial voltage measurement (d) shows that the DAC is currently outputting 0volts.Īn I2C start condition ().Īfter updating the DAC to 100%, a voltage measurement (d) shows that the output is 2.5volts.Ī similar command sequence sets the DAC output back to 0. The global address is useful for controlling multiple DACs simultaneously over the same I2C bus. The DAC responds to the set address (0X40) and a global address (0圎6). Instead of looking up the address in the datasheet, we used the Bus Pirate’s I2C address search macro to scan the entire I2C address range. The state of pin 1 and 8 determine the LTC2631A I2C address, according to the table on page 22 of the datasheet. Additionally, the monitor shows that 5volts is connected to the pull-up resistor supply terminal (VPULLUP). Now, setup the Bus Pirate for I2C mode and activate the on-board power supply.Īfter configuring the Bus Pirate, the voltage monitor shows that the 5volt supply is active (4.9volts). Close the jumpers on the clock and data lines to supply the external voltage to the pull-up resistors. 5volts is supplied to the pull-up resistors by connecting a wire from the 5volt supply to the pull-up resistor input terminal. The I2C bus requires pull-up resistors on both bus wires. We powered the chip from the Bus Pirate’s 5volt supply, but it would also work fine at 3.3volts. The connections between the Bus pirate and the LTC2631A are outlined in the table.
Analog to digital converter i2c serial#
We used the Bus Pirate universal serial interface tool to work with the DAC, but the same basic principals apply to any custom implementation. We previously demonstrated the LTC2640 with a three-wire SPI interface, but this version is controlled with only two signal wires. This DAC can output 255 different voltages, spaced evenly between 0 and 2.5volts. Linear Technology’s LTC2631A-LZ8 is an 8bit digital to analog converter (DAC) with an I2C interface.