Fixed barcode scanner to DeltaV: serial interface and reader choice

You have a bench station to build. A bin lands in a fixture with its barcode label in the same spot every cycle, the label face sits 100-150 mm from the lens, and the decoded lot number has to reach DeltaV for comparison against the batch record. Two decisions carry the whole job. The electrical one: which serial signal the reader hands the controller, and how it is wired. The optical one: how much reader the label's mil width actually demands at that standoff. This guide gives the wiring, the dataset mapping and the sizing arithmetic with real numbers, then a bench test that proves the pair before you commit hardware.

The decision in one paragraph

Buy a fixed-mount reader with an RS-232 output from the fixed code readers range, wire it to the DeltaV serial interface card on shielded low-capacitance cable, and print the label at 20 mil if you own the artwork. Hold the standoff at 110 mm, mid-band of the 100-150 mm you have, with a 120 mm field of view; a 1.2 MP class sensor then puts 5 pixels on every 20 mil module. Run 9600 baud, 8 data bits, no parity, 1 stop bit, and land the string in one dataset sized to the lot code plus 2 bytes. A 10 mil label is the one case that changes hardware: hold the field to 90 mm, or take a 2560-pixel sensor and keep the tolerance.

What the DeltaV serial card expects

The S-series Serial Interface card is the target: the controller auto-senses the card and presents its configuration options, so the work sits in two places — the serial settings and the dataset that receives the string. Set both ends identically:

• Baud: 9600 to start; 115200 when the cable run is short and you want headroom.
• Frame: 8 data bits, no parity, 1 stop bit.
• Handshake: none. A static bin sends one short burst per cycle; nothing overruns.
• Dataset: one ASCII string, length set to the longest lot code plus 2 for the CR/LF terminator — a 10-character code needs 12 bytes, so allocate 16 and leave growth room.

The reader's only job is clean, terminated ASCII. Strip any preamble or suffix before the string leaves the reader — barcode scanner capture without a prefix covers the framing traps that corrupt dataset mapping. If your controller were a PLC instead of a DCS, serial integration on a CompactLogix controller walks the same mapping exercise on that platform.

Size the reader by mil width and standoff

Mil width is the label's narrowest bar, X, in thousandths of an inch: 20 mil is 0.508 mm, 10 mil is 0.254 mm. A decoder needs at least 3 pixels across that bar to find its edges, and 5 to decode with margin. That one rule converts the label into a field-of-view budget:

Worked example: 10-character Code 128 at 20 mil

Take a 10-character lot code, X = 0.508 mm:

• Symbol width: (11 x 10 + 35) x 0.508 = 145 x 0.508 = 73.7 mm
• Quiet zones: 20 x 0.508 = 10.2 mm, so the printed label is 73.7 + 10.2 = 83.9, call it 84 mm
• Fixture tolerance: the bin lands within ±18 mm, so the field of view is 84 + 36 = 120 mm
• A 1.2 MP class sensor spans 1280 pixels: pixel footprint = 120 / 1280 = 0.094 mm
• Pixels per module: 0.508 / 0.094 = 5.4 — above the 5 you want, nearly double the 3 you need

Print the bars 25 mm (1 in) tall. At 0.094 mm per pixel that is 266 pixels of bar, so a tilted bin or an off-angle scan line gives up nothing.

The same math at 10 mil

Halve X to 0.254 mm and the label shrinks to about 42 mm, but the same 120 mm field now puts 0.254 / 0.094 = 2.7 pixels on each module — under the 3-pixel floor, and marginal codes read intermittently rather than failing outright. Pick one fix:

• Tighten the field to 90 mm: 90 / 1280 = 0.070 mm per pixel, and 0.254 / 0.070 = 3.6 pixels per module. Works, but the placement tolerance drops from ±18 mm to about ±8 mm, so the fixture must grip harder.
• Keep the 120 mm field and double the pixels: 120 / 2560 = 0.047 mm per pixel, and 0.254 / 0.047 = 5.4 pixels per module — the margin the 20 mil label had, tolerance intact.

Module width sets decode margin wherever barcodes are read; barcode module width for document scanning shows the same floor from the print side.

Wire the RS-232 link

Three signals do the job: reader TX to card RX, card TX to reader RX — crossed, not straight — and one signal ground common to both. Land the shield on ground at the controller end only. RS-232 is single-ended with a capacitance budget near 2500 pF, which in practice means 15 m of cable at 9600 baud and less at 115200. Run low-capacitance shielded cable the whole way; unshielded general-purpose cable routed near drives picks up enough noise to turn clean reads into framing errors at the card.

On the reader end, one family covers the mechanical side. The MV-IDA-PE-M12A17pF-openRJ45DB9-HF-5m runs from a 17-pin M12 at the reader to open leads, RJ45 or DB9 at the host, 5 m, high-flex. Match the host-side pins to the card terminal per the reader's serial pinout.

If the run exceeds 15 m or shares a tray with drive cables, switch both ends to RS-422/485 and set the card to its 485 mode: differential pairs ignore induced noise and run well past 100 m. RS-232 scanner wiring to an embedded host shows the pinout side of the same link, and a worked serial scanner interface setup on a PLC port covers the controller-side exercise step by step. Browse code reader cables for lengths beyond 5 m.

Trigger and dataset mapping

Trigger the reader from a photoeye that sees the bin land, debounced 100 ms, rather than free-running: one frame per cycle, one string per frame, and the controller compares a value that changes once per bin. If the host must command the reader, the same serial line carries the trigger — diagnosing silent serial scan commands covers the handshake failures that follow. In the logic, compare each incoming string to the previous one before acting; planning a barcode reader PLC communication link applies the same discipline to PLC targets.

Interface paths compared

For one bin station feeding a lot comparison, the decision is RS-232 direct. In the fixed code reader finder, filter Interface to Serial and shortlist from that subset — the compact body that matches your standoff is the one.

The readers for this station

Distance fit first, standoff fixed at 110 mm. The LS-CRD-0047 is a 1.2 MP compact fixed reader with a 60-120 mm reading distance and a USB 2.0 interface. That window puts the standoff in its middle; the USB side makes it a bench bring-up tool while the production link lands over serial. A bin that must sit at the far end of the band needs a longer-distance body instead.

For the 10 mil label, step up in pixels. The LS-CRD-0028 carries a 2560 x 2048 sensor behind an 8 mm lens and decodes up to 60 codes/s. At 2560 pixels across the same 120 mm field it holds 5.4 pixels per module — full placement tolerance on the tighter label. The 30 fps capture rate leaves room for retry logic if a PC ever joins the path.

For the serial output itself, the native example is bigger than the job but shows the pattern. The MV-ID6200PM-00C-NNG is a 20 MP logistics code reader with a Serial interface, a 1-inch sensor and a C-mount. That is tunnel-grade hardware for one bin station; take it as the shape of the Serial subset, then pick the compact equivalent that fits your standoff.

For glare off a glossy label, a polarizing lens cover from reader accessories does at the lens what barcode preprocessing for rotation, blur and glare does in software — and the lens fix needs no PC in the loop.

Bench test before you commit

1. Print the production label — same printer, same substrate, 20 mil, 25 mm bars — and fix it in the real fixture at 110 mm.
2. Capture 50 hand placements. Accept 50 of 50 clean decodes: a static bin at 5.4 pixels per module has no excuse for a miss.
3. Put a scope on the reader's TX line: idle near -12 V, swinging to +12 V on data, clean bit edges, no ringing.
4. Watch the dataset for 50 cycles: 50 strings, right length, terminator present, no split reads.
5. Move the bin to the tolerance extremes, ±18 mm on both axes, and repeat 10 placements at each — 10 of 10 at every extreme.
6. Save the reader configuration to disk and version it; vision reader configuration backup before anything else changes on the station.

When the usual answer is wrong

• A 10 mil label on glossy paper over a 120 mm field fails quietly at 2.7 pixels per module — fix the field or the pixel count, not the lighting.
• The cable run crosses a drive cabinet or exceeds 15 m: RS-232 is the wrong pair. Go RS-422/485 at both ends.
• More stations join later on one 485 trunk: give every reader a fixed address and identify scanners by serial number after reconnects so a swapped unit never writes to the wrong dataset.
• Someone hands you a handheld scanner instead: it is a keyboard-style device, and getting a handheld scanner to a PLC without Ethernet is the closest analogue for a wired desk job.
• The bins arrive already moving on a conveyor: a static-station reader class will not freeze motion. Budget for a reader rated at the line speed and strobe at 1 ms or faster.

Checklist before you order

• Label X measured with a loupe — 20 mil or 10 mil decides the sensor class on the 3-pixel floor.
• Standoff fixed by the fixture and inside the reader's printed reading window; 110 mm for this band.
• Serial subset shortlisted; RS-232 run under 15 m, or RS-485 from day one.
• Lot code length known; dataset sized to code plus 2 bytes — 16 for a 10-character code.
• 9600 8N1, no handshake, photoeye trigger debounced 100 ms, written into both configuration sheets.
• 50 of 50 static decodes and 10 of 10 at each tolerance extreme before the purchase order is final.
• Shield grounded at the controller end only; laser beam below sight line or shielded.

When the station is sized, build it in the configurator or send the label artwork with a quote request — and if the DeltaV side needs a hand, contact the applications team.