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
Sign up to send

Files

Schematic

Layout

Preview

U3
J1 2 - J2 2
C1 P2 - C2 P2
GND
C10 P2 - C11 P2
U1 MODE - IC1 ANODE
GND
J1 2 - J2 2
GND
R32 P2 - C27 P2
U2 AIN5 - U2 AIN6
U2 AIN8 - U2 REFIN2(+)/AIN9
U2 AIN5 - U2 AIN6
R34 P2 - R35 P2
GND
GND
R34 P2 - R35 P2
C1 P2 - C2 P2
C1 P2 - C2 P2
R34 P2 - R35 P2
U3 INPUTS_B_1 - U3 INPUTS_B_2
R32 P2 - C27 P2
J1 2 - J2 2
U1 MODE - IC1 ANODE
GND
GND
U2 AIN5 - U2 AIN6
C1 P2 - C2 P2
C1 P2 - C2 P2
C23 P2 - C24 P2
GND
GND
C1 P2 - C2 P2
U1 MODE - IC1 ANODE
GND
GND
GND
GND
C14 P2 - C15 P2
C1 P2 - C2 P2
GND
U2 AIN8 - U2 REFIN2(+)/AIN9
U11 GND - C25 P2
GND
R34 P2 - R35 P2
C1 P2 - C2 P2
J1 2 - J2 2
GND
GND
C23 P2 - C24 P2
U3 INPUTS_B_1 - U3 INPUTS_B_2
GND
R35
Resistance
5.36kΩ
U6 SIG_B_OUT/IN - U2 AIN1
R2
Resistance
30kΩ
J9
R36 P1 - U1 IMON
R21 P1 - IC1 CATHODE
R5
Resistance
10kΩ
U1 ~{FLT} - J10 15
U2 ~{RDY} - J9 NJTRST
U4 ~OE - R23 P2
R3
Resistance
10kΩ
R34
Resistance
10kΩ
R21 P1 - IC1 CATHODE
R36 P1 - U1 IMON
U10 EN - C19 P1
U6 SIG_C_OUT/IN - R5 P1
R2 P2 - R3 P1
Y1 P1 - U2 XTAL1
U2 SCLK - J9 JTCK
U10 VOUT - C20 P1
U2 ~{RESET} - R24 P2
U3 OUTPUT_A - R25 P2
R21
Resistance
2.2kΩ
R33 P2 - R34 P1
U4 QC - U6 CONTROL_C
U10 VOUT - C20 P1
R31
Resistance
143kΩ
U4 ~SRCLR - R22 P2
J10 02 - U10 VIN
U4 QD - U6 CONTROL_D
R35 P1 - U1 ILIM
U4 ~SRCLR - R22 P2
U1 OUT - C22 P1
C26 P1 - U1 dVdT
R30
Resistance
100kΩ
U6 SIG_B_OUT/IN - U2 AIN1
U1 IN - C27 P1
U10 VOUT - C20 P1
R25
Resistance
10kΩ
U2 DIN - J9 JTDI
U10 VOUT - C20 P1
Y1 P2 - U2 XTAL2
U6 SIG_B_OUT/IN - U2 AIN1
U4 RCLK - J10 09
U1 OUT - C22 P1
R2 P2 - R3 P1
U10 VOUT - C20 P1
U10 VOUT - C20 P1
Y1 P2 - U2 XTAL2
R33
Resistance
274kΩ
U10 VOUT - C20 P1
U10 VOUT - C20 P1
U2 SCLK - J9 JTCK
U2 SCLK - J9 JTCK
U2 DIN - J9 JTDI
U2 ~{CS} - J9 JTMS
U1 IN - C27 P1
R33 P2 - R34 P1
R24
Resistance
100kΩ
R4
Resistance
165Ω
R1 P2 - R2 P1
U2 DOUT - J9 JTDO
U4 QD - U6 CONTROL_D
U2 DOUT - J9 JTDO
U4 ~SRCLR - R22 P2
Y1 P1 - U2 XTAL1
R31 P2 - R32 P1
Y1 P2 - U2 XTAL2
U10 VOUT - C20 P1
R22
Resistance
100kΩ
U2 DIN - J9 JTDI
R33 P2 - R34 P1
R1 P2 - R2 P1
R1 P2 - R2 P1
R1 P2 - R2 P1
U10 EN - C19 P1
U10 VOUT - C20 P1
U2 ~{RESET} - R24 P2
R31 P2 - R32 P1
U2 DOUT - J9 JTDO
U11 OUTPUT_A - R27 P2
J1 1 - R1 P1
R29 P2 - R30 P1
U6 SIG_D_OUT/IN - U3 INPUTS_A_1
U1 IN - C27 P1
U2 ~{RDY} - J9 NJTRST
R31 P1 - U1 IN
R2 P2 - R3 P1
U2 ~{RESET} - R24 P2
C26 P1 - U1 dVdT
J10 02 - U10 VIN
U10 VOUT - C20 P1
J1 1 - R1 P1
U10 VOUT - C20 P1
R31 P2 - R32 P1
U4 QB - U6 CONTROL_B
R1
Resistance
1kΩ
Y1
U11 OUTPUT_B - J10 15
U10 VOUT - C20 P1
R31 P1 - U1 IN
U3 OUTPUT_A - R25 P2
R29 P2 - R30 P1
U10 VOUT - C20 P1
U10 VOUT - C20 P1
U2 SCLK - J9 JTCK
U4 ~OE - R23 P2
R29
Resistance
100kΩ
U1 IN - C27 P1
R21 P1 - IC1 CATHODE
U4 ~OE - R23 P2
U10 VOUT - C20 P1
R32
Resistance
10kΩ
U10 VOUT - C20 P1
J1 1 - R1 P1
U4 RCLK - J10 09
U10 VOUT - C20 P1
U2 ~{CS} - J9 JTMS
U10 VOUT - C20 P1
U10 VOUT - C20 P1
U6 SIG_C_OUT/IN - R5 P1
R29 P2 - R30 P1
R1 P2 - R2 P1
U3 OUTPUT_A - R25 P2
U4 QA - U6 CONTROL_A
R35 P1 - U1 ILIM
U2 ~{RDY} - J9 NJTRST
U4 QA - U6 CONTROL_A
U10 VOUT - C20 P1
U10 VOUT - C20 P1
U10 VOUT - C20 P1
U4 QB - U6 CONTROL_B
J10 02 - U10 VIN
R21 P1 - IC1 CATHODE
Y1 P1 - U2 XTAL1
U2 DIN - J9 JTDI
U4 QC - U6 CONTROL_C
R23
Resistance
100kΩ
U6 SIG_D_OUT/IN - U3 INPUTS_A_1
R36
Resistance
20kΩ
U2 ~{CS} - J9 JTMS
U10
J10
U1
IC1
U2
H2
J1
H3
U6
U4
D1
H4
H1
C22
Capacitance
47µF
C20
Capacitance
10uF
C18
Capacitance
100nF
C27
Capacitance
1µF
C24
Capacitance
12pF
C10
Capacitance
100nF
C19
Capacitance
10uF
C7
Capacitance
100nF
C3
Capacitance
100nF
C2
Capacitance
100nF
C6
Capacitance
100nF
C8
Capacitance
100nF
C4
Capacitance
100nF
C9
Capacitance
100nF
C23
Capacitance
12pF
C1
Capacitance
100nF
C21
Capacitance
100nF
C26
Capacitance
12nF
Validation Status — Universal I/O Controller
Updated: 2026-05-09
Current PCB validation state
A fresh physical-design validation was run for the Universal I/O Controller PCB.
Checks performed
  • Airwire verification
  • Overlapping copper verification
  • Dangling trace verification
  • Invalid layer verification
  • Layout inspection around the previously reported U1/R33 overlap area
Results

Table

CheckLatest stateNotes
Overlapping copperClearThe U1 IN / R33 copper overlap was resolved by moving R33 away from U1 while keeping it in the LM76202 input support area.
Dangling tracesClearNo stale/dangling trace errors were reported after the R33 move.
Invalid layer assignmentsClearNo invalid-layer errors were reported.
Airwires181 remainingThe board still has unrouted physical connections. These must be routed before fabrication.
Notable resolved item
  • The previously reported overlap participant UID 48424081-fdf4-4b9d-8f64-be8156e8842a was identified as R33.
  • R33 was moved to clear U1 while remaining close to the LM76202 input support cluster.
  • Post-move validation reports no overlapping copper, dangling-trace, or invalid-layer errors.
Remaining blocker
The PCB is not fabrication-ready because 181 airwire errors remain. Physical trace routing still needs to be completed for all remaining unrouted nets, then DRC must be re-run until airwires are zero.

  • Current PCB validation state

  • Checks performed

  • Results

  • Notable resolved item

  • Remaining blocker