Problem w. Bluetooth module: No response to AT commands

Wireless & IoT
1

I do not get any response when sending AT commands to the BT module. It treats the commands as if they were data (i.e. ATMC is treated as data and appears at the UART’s TX pin).

According to the datasheet this happens in “fast data mode”, which I did not enable. Moreover, I resetted the module to the factory settings (which I did never change in the first place) via a 10K resistor to Vdd on PIO4. This did not help.

I can send and receive data via Bluetooth and via the hardware UART. Everything works fine as far as data transmission is concerned.

But if I am not able to change e.g. the baudrate, then the module is pretty useless.

Does anyone have another suggestion on how to enable AT command mode ( I tested “ATMC” plus both via BT and UART (in connected and unconnected state) and I also tested resetting the device via PIO4)?

2

Are you sending the string to jump into command mode? The factory default is “+++” followed by a CR as it was on most modems. You should get something like the following (sent strings start wtih >, received with <)

+++

< OK

ATSI,1

< 112233445566

ATMD

< OK

At this point you’re back in data mode, and characters go through the UART.

3

I did only send “ATMC” plus carriage return. This is what the “AT command Rev. 1.2.7” datasheet for the BlueRadios SMT Module says is required to enter command mode when in data mode.

The datasheet does not say anything about “+++”. But I just checked the “BlueSmirf” datasheet and voila: There is your suggested +++ to enter command mode. Do I have an old version of the AT command datasheet :?:

I’ll try out the +++ tonight. Thank you for the suggestion!

4

The copy of the docs I have is labeled “Rev. 2.8.1.0.0”, which is the same version returned by sending “ATVER,ver1” to the module.

The only reference to “ATMC” I see in my copy of the documentation is under “3.3 Command/Data Modes” “1) Fast Data Mode”

…

To verify you are in fast data mode type +++ it will pass directly through the UART because the AT Command

parser is off. Else the +++ will be accepted because the AT Command parser is still on and returns “OKâ€

5

Many thanks daemondust!

Obviously BlueRadios changed the firmware and replaced ATMC with +++, rendering my datasheet useless. And without getting into command mode, the device didn’t tell me that my docs from last fall didn’t match the firmware version…