Array 3311 RS-232C to TTL Adapter for Array 364X/371X

Overview

Array instruments expose a TTL-level serial port. The 3311 translates PC RS-232C to TTL, ensuring correct logic levels and robust communication for scripting, automation and data logging.

Where It Fits

• 3644A/3645A/3646A Array 364X PSU series
• 3710A/3711A/3715A Array 371X DC loads

Why It Matters

Choosing Alternatives in the Series

Competitive Landscape

Getting Started

1. Set instrument address and baud (e.g., 9600 8-N-1) via the instrument menu.
2. Use a straight-through DB9 RS-232 cable PC ⇄ 3311. The 3311 connects to the instrument’s TTL-level port.
3. Send a status query frame to confirm communication, then enable remote control and output/load as needed.

Wiring Quick-Start (364X & 371X)

Minimum Signals You Need

RTS/DTR hardware flow control is not used by these models; leave it disabled in software. If you get no replies, swap to a null-modem RS-232 cable only on the PC⇄3311 leg and retest.

Serial Defaults (Factory)

Command Frames & Code Snippets

These models use a simple 26-byte binary frame (header 0xAA, address, command, payload, checksum). Checksum is the unsigned sum of bytes 1–25 (mod 256). Below are safe “first actions” you can send to verify comms and toggle control.

364X Power Supplies — Read Status & Enable Output

• Query status: Command 0x81 (26-byte frame). Returns V, I, P and flags.
• Set control: Command 0x82 with Byte4 bits: b1=1 Remote, b0=1 Output ON.

# Python 3 + pyserial
import serial

def make_frame(addr, cmd, payload=b""):
    frame = bytearray(26)
    frame[0] = 0xAA
    frame[1] = addr & 0xFE          # instrument address
    frame[2] = cmd & 0xFF
    payload = (payload or b"")[:22] # bytes 4..25 available
    frame[3:3+len(payload)] = payload
    frame[25] = sum(frame[:25]) & 0xFF
    return bytes(frame)

def send_recv(port, frame):
    with serial.Serial(port, 9600, bytesize=8, parity='N', stopbits=1, timeout=1) as s:
        s.write(frame)
        return s.read(26)

ADDR = 0x00  # default
# 1) Read PSU status
resp = send_recv("COM3", make_frame(ADDR, 0x81))
# bytes 4..11 carry I (mA), V (mV), P (mW) little-endian groups
I_mA = resp[3] | (resp[4] & 0xFF) << 8
V_mV = (resp[5] | (resp[6] & 0xFF) << 8 | (resp[7] & 0xFF) << 16 | (resp[8] & 0xFF) << 24)
P_mW = resp[9] | (resp[10] & 0xFF) << 8

# 2) Remote + Output ON (Byte4 = 0b00000011)
resp = send_recv("COM3", make_frame(ADDR, 0x82, bytes([0x03])))
print("PSU status read; output enabled.")

To set limits and a voltage setpoint, use command 0x80 (max current, max voltage, max power, Vset). Start by reading status first to confirm framing and checksum handling.

371X Electronic Loads — Read Status & Turn Load On

• Query status: Command 0x91 (returns I, V, P and limit fields).
• Set control: Command 0x92 with Byte4 bits: b1=1 Remote, b0=1 Load ON.

# Read 371X status then enable load
ADDR = 0x01  # example non-default address
resp = send_recv("COM3", make_frame(ADDR, 0x91))
I_mA = resp[3] | (resp[4] & 0xFF) << 8
# Voltage is reconstructed little-endian 32-bit then scaled
V_mV = (resp[5] | (resp[6] & 0xFF) << 8 | (resp[7] & 0xFF) << 16 | (resp[8] & 0xFF) << 24)
P_mW = resp[9] | (resp[10] & 0xFF) << 8

# Remote + ON
resp = send_recv("COM3", make_frame(ADDR, 0x92, bytes([0x03])))
print("Load status read; load enabled.")

Typical Troubleshooting

• No response: Confirm baud, address, straight-through cable on PC⇄3311, and shared GND. Try a different COM port.
• Framing errors: Replace cable with shielded DB9; keep total run short; ensure only one level shifter (the 3311) is in the path.
• Wrong instrument responds: Each unit has an address; set unique addresses via the front panel.

Why This Helps You Ship Faster

With the 3311 handling level translation and the example frames above, you can verify communications in minutes, then wrap higher-level control in your preferred language or NI-VISA workflow for regression tests, sweeps and long-duration logging.