I have bluetooth module rn42 I need to configure it to 7-bit data mode. Data sheets says that I should use command S7,1 to enable 7-bit data mode, but it does not work. I receive ERR when sending s7,1 or s7,0. Also, i noticed that command SB,1 also returns ERR.

Module lists all available commands when you send him "H" command, and in my case commands S7, and SB, are not in the list… Maybe anybody has some more info about this strange case. I really need to make it work with 7 bit data mode. Firmware version is 6.15 Other commands works fine. Thanks for answers.

  • \$\begingroup\$ Pure guess but what happens if you send a SL,E first to enable even parity? Maybe it doesn't like 7 bits without parity. \$\endgroup\$
    – PeterJ
    Dec 27, 2013 at 13:12
  • \$\begingroup\$ At first glance it looks like a firmware version issue, i.e. the S7 command may have been deprecated by v6.15. Have you checked the v6.15 manual? Also, even if you can't get the RN42 to do 7-bit data, if you explain your problem in more detail someone may be able to offer an alternate solution. \$\endgroup\$
    – markt
    Dec 27, 2013 at 23:08
  • \$\begingroup\$ I checked the Firmware revision history on the manual, it says nothing about 7 bit data mode. The problem is quite simple, i want to connect this module to Crouzet PLC, and Crouzet PLC uses 7 bit data mode for all connections. Crouzet offers their own bluetooth module but its not available, Crouzet says it will be available only in April. \$\endgroup\$
    – PauliusM
    Dec 30, 2013 at 6:30

1 Answer 1


I contacted microchip support team, here are their answer:

Problem Resolution: Hello,

I found that 7-bit data mode does not appear to be supported by v6.15 firmware. This has been captured as a bug, though I don't know if or when it will be added to future firmware. I'll ask that the release notes be modified to include this limitation.

If 7-bit data mode is required, I'd recommend ordering modules with v4.77 firmware. This can be done by contacting your local Microchip sales office. The part number is: RN42-I/RM477

Best regards,


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