GSAS DAC for ADC Interface

The 8255 PPI port output is latched and presented as input to the DAC. The same 8 bits are displayed by a column of 8 LEDs. The DAC output and the analog input are fed to a comparator whose output can be monitored through a port line. This bit will be high when the DAC output is less than the analog input, indicating that a larger digital input value is required. This line can be monitored to determine the digital equivalent of the analog input voltage.

This loopback configuration enables a unique set of experiments that demonstrate both conversion directions simultaneously. Students can quantify DAC linearity by sweeping all 256 output codes and reading back the ADC result, measure differential and integral nonlinearity errors, observe quantisation effects by comparing the original digital value with the ADC readback, and study the relationship between DAC settling time and ADC conversion accuracy. The module is particularly effective for teaching the concept of signal chain accuracy, how errors accumulate through successive conversion stages, a critical design consideration in data acquisition systems. When used alongside an oscilloscope connected to the test points, students can directly visualise the staircase waveform from the DAC and correlate it with the ADC digital output.

Specifications

Parameter	Value
Part Number	IF-DADC
DAC	8-bit digital-to-analog converter
ADC	8-bit analog-to-digital converter
Signal Path	DAC output internally routed to ADC input
Test Points	DAC output, ADC input (labelled for probing)
Bus Interface	Standard GSAS trainer bus connector
Power	Supplied from trainer kit

Lab Experiment Coverage

Experiment Category	Topics
DAC Operation	Digital-to-analog conversion, staircase waveform generation
ADC Operation	Analog-to-digital conversion, successive approximation
Loopback Verification	Write-read cycle, conversion accuracy measurement
Linearity Analysis	DNL, INL measurement across full code range
Quantisation	Quantisation error observation, bit resolution effects
Signal Chain	Cumulative error analysis through DAC-ADC chain

Compatibility

The IF-DADC module connects to all current GSAS microprocessor trainer kits through the standard expansion bus connector:

• GSAS 85A Microprocessor Trainer
• GSAS 86E Microprocessor Trainer
• GSAS 51E Microcontroller Trainer

No additional wiring or external power supplies are required, the module draws power and bus signals directly from the trainer.

Why GSAS

GSAS manufactures the DAC for ADC Interface in Bangalore as part of its analog I/O peripheral module range. The loopback architecture is a pedagogically powerful approach, students see the complete conversion chain in a single experiment, building a concrete understanding of how digital values become analog voltages and back again. This understanding is foundational for anyone working with data acquisition, sensor systems, or mixed-signal embedded design. The GSAS education products team provides lab manual content for DAC-ADC interfacing experiments aligned with Indian university embedded systems curricula.

Products are available for immediate purchase through the GSAS online store (“Buy on Store”) or through direct engagement for institutional and volume orders (“Request Volume Pricing”).