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Mixed-voltage logic in one script

Every one of the 32 I/Os carries its own programmable output levels and input thresholds, anywhere from 1.0 V logic to 24 V industrial signalling. That means a board with a 1.8 V controller on one side and 24 V field I/O on the other is tested by a single AT1032S, with no level shifters, no interface relays and no second instrument.

The AT1032S drives and reads 1.8 V logic on DA4 and DA5 while driving and reading 24 V field I/O on DA8 and DA9, with no level shifters between it and the board.

Four pins, two voltage worlds, one device. Each pin's levels are set in software.

Wiring​

AT1032SDevice under testLevels
DA4Controller inputoutput, 1.8 V logic
DA5Controller outputinput, 1.8 V thresholds
DA8Field inputoutput, 24 V logic
DA9Field outputinput, 24 V thresholds

The test sequence​

import { AT1000 } from '@ikalogic/at1000';

// ---- The two voltage domains on the board ---------------------------------
const LOW = {                       // 1.8 V controller side
  name: '1.8 V controller',
  out_io: 4, in_io: 5,
  voh: 1.8, vol: 0.0,               // what we drive
  vih: 1.2, vil: 0.6,               // how we read the board back
};
const HIGH = {                      // 24 V field side
  name: '24 V field I/O',
  out_io: 8, in_io: 9,
  voh: 24.0, vol: 0.0,
  vih: 11.0, vil: 5.0,
};
const PROPAGATION_MS = 50;          // time the board needs to react
// ---------------------------------------------------------------------------

const sleep = (ms) => new Promise((resolve) => setTimeout(resolve, ms));

const devices = await AT1000.findDevices();
const tester = await AT1000.open(devices[0]);
await tester.reset();

// Configure both domains up front. Each pin keeps its own levels.
for (const domain of [LOW, HIGH]) {
  await tester.gpio.digital(domain.out_io).configure_output({
    voh: domain.voh, vol: domain.vol,
    vih: domain.vih, vil: domain.vil,
    value: false,
  });
  await tester.gpio.digital(domain.in_io).configure_input({
    vih: domain.vih, vil: domain.vil,
  });
}

// Drive each level on the domain's output and confirm the board's output follows.
async function checkDomain(domain) {
  const driver = tester.gpio.digital(domain.out_io);
  const reader = tester.gpio.digital(domain.in_io);
  const results = [];

  for (const level of [false, true, false]) {
    await driver.write(level);
    await sleep(PROPAGATION_MS);
    const seen = await reader.read();
    const ok = seen === level;
    results.push(ok);
    console.log(
      `${domain.name}: drove ${level ? 'HIGH' : 'LOW '} ` +
      `at ${level ? domain.voh : domain.vol} V, ` +
      `read back ${seen ? 'HIGH' : 'LOW '} -> ${ok ? 'ok' : 'MISMATCH'}`);
  }

  await driver.write(false);
  return results.every(Boolean);
}

const lowOk = await checkDomain(LOW);
const highOk = await checkDomain(HIGH);

console.log('');
console.log(`1.8 V side: ${lowOk ? 'PASS' : 'FAIL'}`);
console.log(`24 V side:  ${highOk ? 'PASS' : 'FAIL'}`);

await tester.reset();

Adapting it to your board​

  • Change voh and vol to the levels your board expects to be driven with, and vih and vil to the thresholds that decide how its outputs are read. Outputs cover 0 to 24 V and input thresholds cover −25 V to +25 V.
  • Add a third domain the same way. Every pin is independent, so 5 V, 12 V and 3.3 V sections can all be driven from the same run.
  • PROPAGATION_MS is the settling time the board needs between the drive and the read.

API used on this page​