# Using Two Sensors on One RS232 Port (Alternating Power?)

**URL:** <https://bristlemouth.discourse.group/t/using-two-sensors-on-one-rs232-port-alternating-power/529>\
**Category:** Dev Kit Support\
**Created:** [July 21, 2025, 2:41pm UTC](https://bristlemouth.discourse.group/t/using-two-sensors-on-one-rs232-port-alternating-power/529 "2025-07-21T14:41:17Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![Everardo](https://avatars.discourse-cdn.com/v4/letter/e/278dde/32.png) [@Everardo](https://bristlemouth.discourse.group/u/Everardo)\
**Post date:** [July 21, 2025, 2:41pm UTC](https://bristlemouth.discourse.group/t/using-two-sensors-on-one-rs232-port-alternating-power/529/1 "2025-07-21T14:41:17Z")

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Hey everyone,

I’m working on integrating two sensors into a Bristlemouth Dev Kit, but I only have one RS232 port available. I understand RS232 is a point-to-point protocol and not meant for multiple devices on the same bus, but I’m wondering if this approach could work:

- **Sensors I’m using:**
  - Mini CO₂ Pro sensor (4-pin RS232)
  - ANB pH sensor (6-pin, supports both RS232 and RS485—but I’m using RS232 for now)

The pH sensor seems to require all six pins connected to work properly, and the CO₂ sensor is just standard RS232.

Here’s my idea:

- Connect both sensors’ RS232 TX/RX lines in parallel to the Dev Kit’s RS232 port.
- Only **power one sensor at a time** , leaving the other completely off (so its TX line isn’t active).
- Alternate them on a 5-minute sampling cycle. So CO₂ runs for 5 minutes, then powers off, and the pH sensor powers on for the next 5 minutes.
- I can extend the sampling window from 10 to 13 minutes if I need to account for warm-up time between transitions.

**Questions:**

- Is this “one-powered-sensor-at-a-time” approach safe or viable for RS232?
- Could having both TX lines connected (even if one sensor is off) cause bus contention, reflections, or other issues?
- Is there a better way to handle this if I don’t have hardware support for a second RS232 port?

Any insight would be super helpful. I don’t have deep experience with RS232 at the electrical level, so I’m trying to avoid causing issues by wiring things incorrectly.

Thanks!

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<div class="post-metadata">

**Author:** ![luk](https://avatars.discourse-cdn.com/v4/letter/l/e480ec/32.png) [@luk](https://bristlemouth.discourse.group/u/luk)\
**Post date:** [July 26, 2025, 12:27am UTC](https://bristlemouth.discourse.group/t/using-two-sensors-on-one-rs232-port-alternating-power/529/2 "2025-07-26T00:27:01Z")

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In case someone would like to do something similar.

Not going too much into the details I think it may be possible to have two RS232 devices connected in parallel and power one of them at a time assuming that both of them have high input impedance on the transmitter’s output when they are turned off, but that may be bit of a stretch.

I think I would try to multiplex UART TX/RX lines before two RS232 transceivers.