Welcome to the new FlexRadio Community! Please review the new Community Rules and other important new Community information on the Message Board.
If you are having a problem, please check the Help Center for known solutions.
Need technical support from FlexRadio? It's as simple as Creating a HelpDesk ticket.

FRStack and Remote PTT

Mike-VA3MWMike-VA3MW FlexRadio Employee, Community Manager admin
edited November 2020 in Third-Party Software

FRStack does support remote PTT since FRStack is SmartLink aware.

Mark provided the information required to use local foot switch.


For the FRStack feature to control MOX via a serial port:

MOX tab

  • MOX Com Port Selection and MOX mode; Toggle or Hold

You can choose to use

  1. DTR DSR pair or
  2. RTS CTS pair

You select which pair on the operations tab.

When operating SmartSDR Remotely you do not have access to the PPT hardware on the Radio. The MOX COM Port feature allows you to use a hand or foot switch to key the transmitter using your remote PC's serial port (or USB port using an inexpensive USB to RS232 Converter).

This feature has two modes;

Hold and Toggle. Hold mode keys the transmitter when the switch is closed and un-keys the transmitter when the switch opens. Toggle mode keys the transmitter on the switch's transition from open to closed and continues to transmit when the switch opens. A second switch transition from open to closed un-keys the transmitter.

Using a standard RS232 serial port; the switch contacts should be connected as follows:

Switch shield / ground to DB9 Ground Pin 5

  1. Switch PPT line to DB9 DSR Pin 6. Connect a 2K resistor between DB9 DSR Pin 6 and DTR Pin 4
  2. Switch PPT line to DB9 CTS Pin 8. Connect a 2K resistor between DB9 CTS Pin 8 and RTS Pin 7

*** I think you will find the resistor value (pull up) is not very critical. Anything from about 1K to 5K should work ***

Note: When you enable this feature (or start FRStack with this feature enabled) without the resistor in place between the DTR and DSR pins of the selected COM Port OR the hand or foot switch in the closed state; FRStack will report an error and disable the feature.

*** The following is for TTL Devices Only - most of you can ignore this part as an RS232 connection is not TTL ***

Using a FTDI TTL (5 Volt) serial port; the switch contacts should be connected as follows:

Switch shield to ground (black); Switch PPT to the CTS line (brown). Connect a 5K resistor between 5V (red) and CTS line (brown)

Note: When my switch was closed the FTDI CTS line is 0 volts which is signal state true.

Leave a Comment

Rich Text Editor. To edit a paragraph's style, hit tab to get to the paragraph menu. From there you will be able to pick one style. Nothing defaults to paragraph. An inline formatting menu will show up when you select text. Hit tab to get into that menu. Some elements, such as rich link embeds, images, loading indicators, and error messages may get inserted into the editor. You may navigate to these using the arrow keys inside of the editor and delete them with the delete or backspace key.