# Cannot enter command mode on RN41

**URL:** <https://community.sparkfun.com/t/cannot-enter-command-mode-on-rn41/14404>\
**Category:** Wireless & IoT\
**Created:** [February 7, 2010, 9:30pm UTC](https://community.sparkfun.com/t/cannot-enter-command-mode-on-rn41/14404 "2010-02-07T21:30:41Z")\
**Posts on this page:** 7\
**Page:** 1

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**Author:** ![arjan](https://avatars.discourse-cdn.com/v4/letter/a/278dde/32.png) [@arjan](https://community.sparkfun.com/u/arjan)\
**Post date:** [February 7, 2010, 9:30pm UTC](https://community.sparkfun.com/t/cannot-enter-command-mode-on-rn41/14404/1 "2010-02-07T21:30:41Z")

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I’m trying to get into remote (i.e. over BT) command mode on a RN41 bluetooth module, but cannot get in.

The module is integrated on a PCB, where the baud pin is high (force 9600 baud) and CTS and RTS pins are bridged.

After pairing i can connect to the RN41 using PuTTY on my PC, and the BT status window says “3 bytes sent” after typing ‘$$$’ (within 60 seconds). I expect a ‘CMD’ response now, but nothing happens…

PuTTY settings are 9600, 8, 1, no parity.

I’ve also tried the default 115k2, which doesn’t work either.

I am out of clues now, can anybody hint me?

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**Author:** ![arjan](https://avatars.discourse-cdn.com/v4/letter/a/278dde/32.png) [@arjan](https://community.sparkfun.com/u/arjan)\
**Post date:** [February 8, 2010, 9:00pm UTC](https://community.sparkfun.com/t/cannot-enter-command-mode-on-rn41/14404/2 "2010-02-08T21:00:01Z")

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Follow up:

I do get data accross and the connect status pin also makes sense, so the module is definitely working.

Could it be that forcing 9600 baud disables (remote) cmd mode?

Next test is to see if I can get into commend mode from teh wired side. This requires some more PIC programming though…

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**Author:** ![leshan](https://avatars.discourse-cdn.com/v4/letter/l/e68b1a/32.png) [@leshan](https://community.sparkfun.com/u/leshan)\
**Post date:** [April 20, 2010, 4:17pm UTC](https://community.sparkfun.com/t/cannot-enter-command-mode-on-rn41/14404/3 "2010-04-20T16:17:40Z")

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Same here. I can’t enter command mode.

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<div class="post-metadata">

**Author:** ![arjan](https://avatars.discourse-cdn.com/v4/letter/a/278dde/32.png) [@arjan](https://community.sparkfun.com/u/arjan)\
**Post date:** [April 20, 2010, 5:41pm UTC](https://community.sparkfun.com/t/cannot-enter-command-mode-on-rn41/14404/4 "2010-04-20T17:41:02Z")

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Let me know if you get any further, I gave up.

Pulled the bitrate to 9600 electronically and shorted CTS/RTS. This brings me what I needed so I get the data connection up, which is nice. However still no command mode. Did not try it from the wired side though…

Arjan

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**Author:** ![mcogill](https://avatars.discourse-cdn.com/v4/letter/m/a4c791/32.png) [@mcogill](https://community.sparkfun.com/u/mcogill)\
**Post date:** [March 26, 2011, 1:06am UTC](https://community.sparkfun.com/t/cannot-enter-command-mode-on-rn41/14404/5 "2011-03-26T01:06:13Z")

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I have had some grief with these modules also. If you put them in master mode, they essentially “brick up”

I broke through this and reset it to factory using an arduino script and having it attached to the tx/rx on the arduino. I did something like this: (and it worked)

void setup()

{

Serial.begin(115200);

Serial.println(“+++”);

delay(20);

Serial.println(“ATFRST”);

delay(100);

Serial.println(“SM,0”);

delay(130);

}

void loop()

{

delay(10);

Serial.println(“$$$”);

delay(100);

Serial.println(“$$$”);

delay(100);

Serial.println(“$$$”);

delay(100);

Serial.println(“$$$”);

delay(100);

Serial.println(“$$$”);

delay(100);

Serial.println(“$$$”);

delay(100);

Serial.println(“ST,255”);

delay(200);

Serial.println(“SM,0”);

delay(120);

Serial.println(“SF,1”);

delay(16000);

Serial.println(“Z”);

}

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<div class="post-metadata">

**Author:** ![arjan](https://avatars.discourse-cdn.com/v4/letter/a/278dde/32.png) [@arjan](https://community.sparkfun.com/u/arjan)\
**Post date:** [March 26, 2011, 6:50am UTC](https://community.sparkfun.com/t/cannot-enter-command-mode-on-rn41/14404/6 "2011-03-26T06:50:13Z")

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> mcogill:  
> …
> 
> I did something like this: (and it worked)
> 
> …

Thanks for posting this. It’s been a while since I worked on my project, but I might give it a try.

Are the delays you mention critical? I don’t know Arduino code, but assume they are msec.

. . . Arjan

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<div class="post-metadata">

**Author:** ![XorLor](https://avatars.discourse-cdn.com/v4/letter/x/8c91f0/32.png) [@XorLor](https://community.sparkfun.com/u/XorLor)\
**Post date:** [April 4, 2011, 6:42am UTC](https://community.sparkfun.com/t/cannot-enter-command-mode-on-rn41/14404/7 "2011-04-04T06:42:34Z")

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Accessing command mode at 9600 shouldn’t be a problem. I got it to work with Putty via my laptop’s internal Bluetooth. Here’s my setup:

reset pin = high

force 9600 pin = high

Auto master pin = low

Auto discovery = high

Once connected, you just send three ‘$’ characters in a row and it immediately replies with “CMD”.