Cheap boards based on the Texas Instruments ADS-1256, a very low noise 24-bit ADC, are provided by many sellers. This boards can be easily integrated into any project, but they can also be used as 4 channels voltmeter to integrate the lab measurement instruments. Working on complex projects having an additional instrument with a good precision may be extremely helpful. GUI-1256 is an iOS and macOS application which transforms a simple ADS1256 board in an additional lab instrument, Bluetooth BLE enabled. GUI-1256 main features are: • 4 Differential voltage measurements. Without any additional components the ADS1256 can read 4 voltages of +/- 3V max. • Bluetooth connection to the measurement device, allowing to get remote measurements • Enabling and disabling any of the 4 available channels • Optional synthesize voice which reads the measurements, allowing to get measurements without looking at the iOS or macOS device • Shifting and scaling. Each of the 4 measurement channels can be independently scaled and shifted • Mathematical Expressions. The measurements can used in mathematical expressions to get other quantities. For example, a temperature sensor voltage can be read, and an expression can be used to directly transform the voltage into the temperature • Graphs (iOS 16 or greater only). Each of the 4 channels and the expressions can be shown as graphs. • Two points calibration to get even more precise measurements • Firmware Over The Air Update. The firmware can be update or upgraded directly from the application. First installation requires Arduino IDE and some additional software components available for free