Cpp
#include <SPI.h>
#include <Wire.h>
constexpr int SCK_PIN=18, MISO_PIN=19, MOSI_PIN=23, NSS_PIN=27;
constexpr int BUSY_PIN=14, DIO1_PIN=13, RESET_PIN=4;
constexpr int RXEN_PIN=16, TXEN_PIN=17;
constexpr int SDA_PIN=21, SCL_PIN=22;
constexpr int BAT_PIN=34, PG_PIN=36, STAT_PIN=39;
void initBenchInterfaces() {
  // Dummy-load bench only; does NOT define welding command policy.
  pinMode(NSS_PIN, OUTPUT); digitalWrite(NSS_PIN, HIGH);
  pinMode(RXEN_PIN, OUTPUT); digitalWrite(RXEN_PIN, LOW);
  pinMode(TXEN_PIN, OUTPUT); digitalWrite(TXEN_PIN, LOW);
  pinMode(BUSY_PIN, INPUT); pinMode(DIO1_PIN, INPUT);
  pinMode(PG_PIN, INPUT); pinMode(STAT_PIN, INPUT);
  pinMode(BAT_PIN, INPUT);
  SPI.begin(SCK_PIN, MISO_PIN, MOSI_PIN, NSS_PIN);
  Wire.begin(SDA_PIN, SCL_PIN); Wire.setClock(100000);
  // RESET sequence and interrupts require reviewed E22 driver timings.
  // No DAC command, EEPROM write or machine actuation here.
}
int readBatteryRaw() { return analogRead(BAT_PIN); }
int readPgRaw() { return digitalRead(PG_PIN); }
int readStatRaw() { return digitalRead(STAT_PIN); }

1. Validate rails and continuity; keep machine physically disconnected.
2. Initialize bench GPIO and bus clocks; confirm charger-status inputs and calibrated battery measurement.
3. Initialize radio using reviewed E22 timings, BUSY handshake and legal region settings. Validate transport on dummy setup before application command handling.
4. Probe approved DAC address and read status/configuration including EEPROM power-up behavior. Do not automatically write a presumed safe analog value.
5. Gate any diagnostic DAC sweep behind explicit operator authorization and isolated dummy load. Calculate output code only after reference/gain/load calibration.
6. Application startup/link-loss/brownout/watchdog/stale-command behavior remains USER DECISION. No placeholder zero/hold/full-scale policy may be shipped; reject production enable until policy and tests exist.