Serial + Power Adapter

  • Overview
  • Support
  • FAQ's

Serial + Power Adapter

Connects an iPhone or iPad to an RS-232 serial device and to power.

This adapter is used in conjunction with the Redpark Serial SDK to create iOS apps that communicate with a serial device. It is licensed through the Made for iPhone (MFI) program for use in private deployments under the terms of an enterprise, education or personal iOS developers license.

Under current Apple policy apps may not be deployed via the public App Store for use with this cable. However apps may be deployed via Apple Business Manager and Apple School Manager.

  • L4-SERP
  • $99
  • 013964221251
  • One year
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Serial Interface

  • Male DB9 connector
  • Max Baud Rate:  115 Kbps


  • 12V 1.6A power adapter
  • barrel jack


  • For use with all iOS devices with Lightning connector
  • Requires iOS 12 or later


  • Length  6 ft


If your Redpark cable is not working properly try these troubleshooting steps below. 

Power your iPhone OFF and then ON again. (Do not simply put the iPhone to sleep. Power it completely OFF and then ON.)

If the problem continues to exist…

Confirm that your iPhone/iPad detects the cable:

  • Connect your cable to the iPhone
  • Open the Settings app on your iPhone
  • Select “General” then select “About”
  • Scroll down the list.   “Serial+Power Adapter” will appear near the bottom of the list if the cable is detected by iOS).

If the iPhone IS detecting the cable:

Check whatever app you are using to make sure that the communication settings (baud rate, parity, etc.)  are properly configured. Check with the app developer if you have questions about the proper configuration.

If the iPhone is detecting the cable and the communication settings are correct but you are still experiencing a problem — perhaps the cable has developed a short in its wiring.   If the cable is within the one year warranty please return the cable to Redpark to be tested.  

If the iPhone IS NOT detecting the cable:

  • Make sure the case on your iPhone is not preventing the cable from being fully inserted into the connector of your iPhone.
  • Use a toothpick or safety pin to remove any debris that might have accumulated in the connector of your iPhone.
  • Try the cable on a 2nd iPhone or iPad to see if you get the same results. If the cable works OK on the 2nd iOS device then it is likely that cable is good.  If the cable does not work on the 2nd iOS device and the cable is within the one year warranty please return the cable to Redpark to be tested. 

 If you choose to email Redpark for assistance, please email “”.

Serial + Power Adapter FAQ

What kinds of devices have serial ports these days?

Point of sale devices, scientific instrumentation, data loggers, RFID readers, automobile engines, routers and other networking devices, glucose meters, fire alarm panels, irrigation controllers, weather stations, specialty printers, scales, temperature sensors, flight loggers, satellite radios, ham radios, model cars (models boats, planes and rockets too), CNC machines and more…

What version of iOS is required?

iOS 12.x or later.

Is there a way to connect to serial devices using TTL (logic level)?

Yes, by connecting an external RS-232 to TTL adapter to the DB-9 connector on the Adapter.

What is the maximum baud rate supported by this adapter?

460 Kbps

How does the adapter connect to an iOS device?

The adapter provides a USB A port. A standard Lightning to USB A cable is used to connect the adapter to an iOS device. A USB-C to USB-A cable is used to connect to an iPad that has a USB-C port.

Why isn’t a Lightning or USB-C cable included with the adapter?

Leaving the choice of cable up to the user allows the user to select the length, color and style of Lightning or USB-C cable that best fits the use case.

What are the specifications of the power supply provided with this adapter?

The power supply that is provided with the Serial+Power Adapter is a 12V 19.2W power supply. Many factors including ripple and noise, switching frequency and efficiency were critical to the selection of this power supply. (You should not assume that any 12V power source is acceptable.)

Doesn’t the iOS device require a 5V power source?

The Serial+Power Adapter converts the incoming 12V power to 5V in order to charge the iOS device.

Can the power adapter be used in markets outside of the United States?

Yes, the power supply is a switching power supply (100-240v). In the United States the Serial+Power Adapter is shipped with a USA style power cord. Our reseller partners in other markets (i.e. Europe, Japan, Australia) offer power cords that are appropriate for their local markets.

Can the adapter be used without the power supply?

No. The adapter must be connected to power in order to operate.

Can I provide power to the serial device using this Adapter?

Some very low power devices make use of the RS232 signal lines to supply power. This usage of the RS232 connection is outside of the RS232 specification and may not work in every instance. It is left up to the user to determine if the RS232 output signals will supply enough power for a particular application. Currently, the L4-SERP uses a MAX3243 or similar driver to convert logic level signals to RS232 level signals. The specifications for the MAX3243 may be used as a rough guide to determine if the signal levels are appropriate for your application. Redpark reserves the right to change the RS232 driver circuitry at any time.

What apps does this adapter work with?

The adapter and SDK are provided to you so that you may write your own apps.

Does the Adapter work with apps available at the App Store?

Apple allows apps to be deployed via Apple Business Manager and Apple School Manager for use with the Serial+Power Adapter. Apps may not be deployed via the public Apple App Store at this time.

How can I tell if my iOS device recognizes the adapter?

Open the “Settings” app on your iOS device. Select “General”, then “About”. If the Serial+Power Adapter is connected properly, it will appear in the list shown.

How do I know what version of firmware the adapter is using?

Once you have located the Serial+Power Adapter in the “Settings” App, select the Serial+Power Adapter to view its parameters.