DB9 cables with your pinout, not ours.
set every pin-to-pin connection yourself — crossovers, skipped pins, twisted pairs, flying leads — and the price follows each change. the null modems below open ready to edit. genuine Amphenol parts · priced instantly · free 2-day shipping.
Price
start from a preset, change any pin.
| build | qty 1, each | qty 10, each | qty 50, each | configure |
|---|---|---|---|---|
| null modem, 3 wires (2↔3, 5–5), 12 in (305 mm) | $40.00order minimum | $21.43 | $20.30 | configure |
| null modem, RTS/CTS crossed too, 12 in (305 mm) | $40.00order minimum | $26.60 | $25.20 | configure |
| null modem, RTS/CTS crossed too, 48 in (1219 mm) | $40.00order minimum | $36.86 | $34.92 | configure |
| straight through, all 9 pins, plug to receptacle, 12 in (305 mm) | $40.00order minimum | $36.90 | $34.96 | configure |
| RS-232 RXD, TXD and ground to 12 in (305 mm) leads with ferrules | $40.00order minimum | $15.67 | $14.84 | configure |
each · free UPS 2-day shipping · $40 order minimum (a smaller order is charged $40) · ships in 10 business days. these are example builds: change the length, pinout and colors in the configurator and it prices the result the same way.
Drawing
the three-wire null modem, pin for pin.
3 wires between two DB9s, 22 AWG in the standard color order. the configurator draws the same diagram for your own pin map and exports it as a PDF.
| end A | end B | wire |
|---|---|---|
| pin 2 RXD | pin 3 TXD | black |
| pin 3 TXD | pin 2 RXD | white |
| pin 5 GND | pin 5 GND | blue |
Pinouts
DB9 pinouts: RS-232, CAN, RS-485.
the same nine pins, four ways. RS-232's is the PC serial port's, standardized as TIA-574, shown from the computer's side; CAN's is CiA 303-1; RS-485 has no standard DB9 pinout, so both published conventions are shown. signals in brackets are optional. pins are numbered on the connector face: 1–5 across the wide row, 6–9 across the narrow one.
| pin | RS-232 | CAN | RS-485 (PROFIBUS) | RS-485 (MODBUS) |
|---|---|---|---|---|
| 1 | DCD | reserved | not connected | Common |
| 2 | RXD | CAN_L | (M24) | (VP) |
| 3 | TXD | CAN_GND | B | (PMC) |
| 4 | DTR | reserved | (CNTR-P) | RXD1 |
| 5 | GND | (CAN_SHLD) | DGND | D1 |
| 6 | DSR | (GND) | VP | not used |
| 7 | RTS | CAN_H | (P24) | not used |
| 8 | CTS | reserved | A | RXD0 |
| 9 | RI | (CAN_V+) | (CNTR-N) | D0 |
sources: Linux Serial HOWTO §19.1, the PC's DB9 serial port; Wikipedia, RS-232 (TIA-574; null modems not in the standard); CiA 303-1 v1.9.0 (2017) §6.1, table 4; CiA now keeps pin assignments in CiA 106; Wikipedia, RS-485 ("does not specify any connector or pinout"); PROFIBUS Interconnection Technology guideline v1.4 (2007), table 3.1-1; MODBUS over Serial Line v1.02 (2006) §3.5.1 and §3.5.2.
Null modem
two computers, one cable.
a straight-through cable joins a computer to a modem; joining two computers means crossing each one's transmit to the other's receive. RS-232 doesn't define that cable, so wirings vary. the three-wire preset crosses TXD and RXD and runs ground straight through; the five-wire one crosses RTS and CTS as well, for hardware flow control.
| pin | signal | what it is | in this build |
|---|---|---|---|
| 1 | DCD | data carrier detect, in | not wired |
| 2 | RXD | receive data, in | black wire → pin 3 |
| 3 | TXD | transmit data, out | white wire → pin 2 |
| 4 | DTR | data terminal ready, out | not wired |
| 5 | GND | signal ground | blue wire → pin 5 |
| 6 | DSR | data set ready, in | not wired |
| 7 | RTS | request to send, out | red wire → pin 8 |
| 8 | CTS | clear to send, in | green wire → pin 7 |
| 9 | RI | ring indicator, in | not wired |
sources: Linux Text-Terminal-HOWTO §12.3, null modem cable pin-out; Wikipedia, RS-232 (TIA-574; null modems not in the standard).
Connector
DB9 (DE-9)
Wire
20–24 AWG
Length
5–48 in (127–1219 mm)
Lead time
10 business days
Questions
about the DB9 custom pinout.
- can I order just one?
- yes, there's no minimum quantity, but there is a $40 order minimum. one 12 in (305 mm) three-wire null modem comes to $22.56, so an order of just that is $40; add more and the minimum is covered. shipping is free (UPS 2-day). prices drop at 10 and 50 units.
- how do I set my own pinout?
- open any row above in the configurator and use the rewire panel: each pin on end A can go to any pin on end B, to a flying lead (with or without a ferrule), or nowhere. wires between the two connectors can be put into twisted pairs. the price and the drawing update with each change, and the share link keeps the whole pin map.
- can one pin connect to two others?
- not in the configurator: each pin takes one wire. that's why the full-handshake null modem, which runs DTR on one end to both DSR and DCD on the other, isn't a preset. jumpers between two pins on the same connector are allowed, as long as neither pin also has a wire.
- is a null modem part of the RS-232 standard?
- no. the standard doesn't cover null modem cables, so there's no official wiring. the presets follow the Linux Text-Terminal-HOWTO: TXD and RXD crossed with ground straight through, and in the second version RTS and CTS crossed too. check what your equipment expects before you order.
- can you build a loopback plug?
- not in the configurator. every build needs at least one wire leaving the connector, and a loopback plug is only jumpers. email the shop and we'll quote it by hand.
- how is it made?
- each wire is tinned and soldered into its contact's solder cup with lead-free solder, then a hood goes over the joints, plastic or zinc, with 4-40 screws to lock it to the mating connector. every cable gets a continuity test.
- what wire gauges and lengths?
- 20, 22, 24 AWG UL1007 hook-up wire, any length, 5–48 in (127–1219 mm). the prices above are at 22 AWG unless a row says otherwise.
- how fast does it ship?
- it's built and shipped in 10 business days, then goes out UPS 2-day.
more in the FAQ, including returns (custom cables are non-returnable; defects replaced).
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