Universal I/O Controller Design

M

michelelmurr

Create a complete new schematic and PCB-ready design for a single-channel Universal I/O controller based on an ATmega328 microcontroller.
Core requirement:
Design a new circuit from scratch. Do not reuse or include LM76202QPWPRQ1, AD7708, HC595, CD4066, LM2902, or other external switching/ADC/control ICs unless absolutely required and explicitly approved. The ATmega328 should directly measure and control the universal I/O as much as practical.
Universal Input requirements:
The same field input connector must support software-configurable modes:
  1. Digital input
  2. Analog voltage input
  3. 0–10 V input
  4. 0–20 mA input
  5. Resistance measurement
  6. RTD measurement: PT1000 and NI1000
  7. Thermistor measurement: 10k Type II and 10k Type III
Universal Output requirements:
Provide a software-configurable universal output from the ATmega328. Include at minimum:
  1. Digital output
  2. PWM-based analog voltage output using filtering/buffering if needed
  3. Clearly document whether true 0–10 V output or 0–20 mA output is supported directly, requires extra circuitry, or is out of scope for the first revision.
Architecture constraints:
  • Use ATmega328 ADC pins directly for measurements.
  • Avoid HC595 shift registers.
  • Avoid CD4066 analog switches.
  • Avoid LM76202 protection IC.
  • Avoid AD7708 external ADC.
  • Prefer simple discrete protection, resistor dividers, shunt resistors, RC filters, jumpers or low-cost analog selection methods if needed.
  • Use clear ALL_CAPS net names.
  • Design for a 24 V industrial field environment where possible, but keep MCU pins protected within safe voltage/current limits.
Expected schematic blocks:
  1. Power input and regulation for ATmega328 logic rail.
  2. ATmega328 core: power pins, reset, clock option, ISP/programming header, decoupling.
  3. Universal input field connector with protection.
  4. 0–10 V divider path into ADC.
  5. 0–20 mA shunt path into ADC.
  6. Resistance/RTD/thermistor divider or excitation path into ADC.
  7. Digital input threshold/protection path into an ATmega328 GPIO.
  8. Universal output connector with digital/PWM output conditioning.
  9. Optional test points and calibration notes.
Implementation expectations:
  • Select suitable components from the Flux library.
  • Add all required resistors, capacitors, connectors, protection parts, regulator, and ATmega328 support parts.
  • Wire the complete schematic.
  • Add Role and Role Details properties to important parts.
  • Run ERC and fix schematic errors.
  • Create a project document explaining the circuit architecture, mode configuration table, ATmega328 pin mapping, ADC scaling equations, firmware configuration notes, and limitations.
  • After schematic validation, set up a reasonable PCB board size and stackup, place components by functional block, and prepare for routing.
Important design notes:
  • Because the ATmega328 has limited ADC resolution and input range, include scaling and protection so all field signals are reduced to the MCU ADC range.
  • Firmware must select the measurement mode and apply calibration/scaling formulas.
  • If fully software-selectable mode switching cannot be achieved without extra analog-switch ICs, propose a simple alternative such as jumpers, resistor option links, MOSFET/discrete switching, or separate input terminals, and document the tradeoff before implementation.

flux

I couldn’t start a new execution plan because a previous execution is currently stopping; once it finishes, I can generate and start the plan for this ATmega328-based Universal I/O redesign.
Use jumper modes
Schematic first
Separate terminals
ATmega328P 5V
Document architecture
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Schematic

Layout

3D View

U6 SIG_B_OUT/IN - U2 AIN1
U10 VOUT - C20 P1
J1 1 - R1 P1
U6 SIG_C_OUT/IN - R5 P1
U6 SIG_D_OUT/IN - U3 INPUTS_A_1
J1 2 - J2 2
GND
J1
U6

Universal I/O Controller

Universal I/O Controller thumbnail