TZT AT-09 Android IOS BLE 4.0 Bluetooth module

Well I bought one of these modules from Aliexpress as I was tired of running around connecting up the serial port with wires and the device was relatively inexpensive to experiment with. Most people will be familiar with the FTDI USART to TTL module but this obvioulsy works in limited range over a Bluetooth wireless link.

So how good is it and was it worth the money? Looking underneath we can see the pinout. I also note some form of switch near the molex connection ;  a reset button perhaps?  I have little data on this but I can see a couple of gotcha's already.  I see on th elower pin of the molex an EN pin . Presumably this is tied either high to supply or to 0V. Given its next to VCC I suspect tied high. VCC is between 3.6V and 6V so 5V sounds a good choice. The main device is CC2541 and purports to be a Texas instruments chip.  CC2541

Link to datasheet URL above.

I am also downloading  Serial bluetooth terminal and this can be used to communicate with the module.  Normal trick with serial communication is that we loopback RXD and TXD and whatever we type we received back on the RXD input. I had installed others but the BLE versions seemed to be more easier to use and it may just have been conflicts. The serial bluetoot terminal worked immediately and provides the loopback copy in a different colour so it is easier to see this has been repeated.

One of the issues I thought I had was the soldering of the BLE module onto the board and I have included some pictures. It seems that themodule connections are not all required to be soldered. But I have asked.  At present the AT commands don't seem to be working.

 

First power up the module with 5V. An LED will flash to show connectivity. Activate Serial Bluetooth Terminal and ensure the bluetooth link is on. The device should be broadcasting as  "MLT-BT05" and you should pair with this.

When pairing the module it was rejected by my phone, so I moved to another software type. I managed to find a basic diagram but I think this module is a later design and you can program the module through the AT commands

The pin-out is therefore:

• CC: +3.3V - 6V but not to exceed 7V.
• GND: Ground  or 0V pin
• TXD: Transmit out Serial Data 
• RXD: Receive in Serial Data
• STATE: The STATE pin is normally LOW and goes active HIGH when link established.
• EN (Enable): Enables or disables module and places into low power state. ( Not sure what current setting).

These last two can be interrogated by an AT command.

So I have loopback working but I would like the PC to communicate via the bluetooth module to my phone.  To do this we will use the FTDI UART to TTL module and cross connect to bluetooth.

Black is GND or 0V
RXD goes to TXD
TXD goes to RXD

The VCC should be set to 3.3V or 5V the FTDI requires a jumper connector for either volyage. The USB then powers the FTDI and the FTDI powers the BLE module.

We then use PuTTY or another PC based terminal program to send out ASCII to your phone.

I am using USART terminal from Mikroelektronika and it allows me to repeatedly send a text message every second.

The result can be seen  on my phone.

This is the final layout... Don't worry about the black lead that is my stereo jack RS232 connection and its not connected. This also works both ways as I can send from bluetooth as would be expected.

The mystery of the AT commands awaits another episode.