BTM511 Series Audio Bluetooth Module

In general, cleaning the populated modules is strongly discouraged. Residuals under the module cannot be easily removed with any cleaning process. 

• Cleaning with water can lead to capillary effects where water is absorbed into the gap between the host board and the module. The combination of soldering flux residuals and encapsulated water could lead to short circuits between neighboring pads. Water could also damage any stickers or labels.
• Cleaning with alcohol or a similar organic solvent will likely flood soldering flux residuals into the RF shield, which is not accessible for post-washing inspection. The solvent could also damage any stickers or labels.
• Ultrasonic cleaning could damage the module permanently.

However, if water washing is required you will need to use deionized water. We do not recommend chemical cleaning and cannot guarantee it will not damage the modules. If you MUST clean PCB with chemicals it is recommended that you test on one board and then confirm the module still works after the process, prior to adding it to production, while understanding the above affects washing the populated PCBs can have on the module.

Our fully-embedded modules have a throughput of around 300-360 kbps.  They have an on-board Bluetooth stack and do all of the Bluetooth processing themselves. Bluetooth 2.1 + EDR has a practical transfer rate of 2.1 Mbit/s, but this is not possible on a small embedded module that does not have a powerful PC-type processor.

Yes, the BTM511 can act as either an A2DP source or an A2DP sink but not both at the same time.

For more information, see our list of  Bluetooth Profiles.

The BTM511 firmware contains AAC technology which incorporates intellectual property owned by numerous third parties. Supply of this product does not convey a license under the relevant intellectual property of those third parties nor imply any right to use this product in any finished end user or ready-to-use final product. An independent license for such use is required.  A license is not required for development purposes. For details, please visit http://www.vialicensing.com.

The BTM511 comes with a full aptX licence included in the price of the module.

For more information, see the BTM51X page.

Currently the BTM511 supports , A2DP, SPP, HFP, HF and AVRCP 1.0.

No, not generally. The DSP in the BTM511 is used for certain audio processing algorithms supplied by CSR such as Clear Voice Capture (CVC) and Music Manager. If you have a specific DSP requirement please contact support.

Based on a scenario between two BTM41x modules (referenced in the BTM41x Low Power Modes Application Note), the role of a device (master/slave) does not have an impact on sniff mode. In the scenario, sniff mode requests were accepted with requested parameters and were applied on the link, regardless of which end they were initiated from. Thus, at least one end must actively request sniff mode at some point after a connection has been created and the other end must at least not reject sniff mode. If the other end requests sniff mode as well, then the parameters of the most recent request will apply to the link.

Again, this has been done between two BTM41x modules. The relevant source code from this scenario was later ported across to the BTM51x. Confirming tests and measurements have not been carried out on the BTM51x. However, there is no obvious reason why it should behave differently on the BTM51x.

Please note that sniff configuration refers to Rfcomm based links :SPP, HSP, HFP. For AVRCP/A2DP there are some a default setting.

It should be possible to evaluate if a remote device requests sniff mode: Disable local sniff mode by setting Sniff parameters to zero (S561- S564, by default these are zero) and while in a connection check ATi13 repeatedly. If the response is ‘1: b,c,d,e’ then sniff mode has been entered, caused by the remote end. The resulting sniff parameters (b,c,d,e) are likely to be the ones requested by the remote end.

When the module is held in RESET, it is considered to be in a deep sleep mode.

Yes, the external I2S circuit should be slave and BTM511 should be I2S master. In addition, the external I2S circuit should not require a high frequency synchronization clock (12 MHz or 24 MHz). The BTM511 is not capable of creating this.

Unfortunately, BTM51x cannot provide such MCLK signal. Laird recommends you select an external codec IC which has the capability of creating the MCLK internally from the bit clock signal (SCK). Such capability is referred to as “PLL” (phase locked loop) or “FLL” (frequency locked loop) functionality of the codec device.

The class of device (COD) format is defined by the Bluetooth SIG on the following webpage:

https://www.bluetooth.org/en-us/specification/assigned-numbers/baseband

The following site can be useful when generating a COD:

http://bluetooth-pentest.narod.ru/software/bluetooth_class_of_device-se…

A good way of understanding COD is to perform an at+btin command and discover the COD of devices around you. For example if you are working on a Bluetooth speaker, use the command at+btin to find out what COD other Bluetooth speakers are using and then refer back to the web pages linked to above.

This article is designed to illustrate the process of Simple Secure Pairing (SSP) when initiated from a BTM module. Introduced in Bluetooth v2.1, SSP creates a bond in a very different way than the legacy PIN pairing many users are familiar with. This is demonstrated both for security level 2 (default) and security level 3.

Security Level = 2

Assumptions:

peer device is BT2.1 (supporting secure simple pairing)

security level of BTM device is

security level of peer device is

the pairing initiating device is aware of the peer device's Bluetooth Device Address

Note:  Connections in Bluetooth v2.1 are always encrypted.

Figure 1:  BTM vs BTM

Figure 2:  BTM vs PC

Security Level = 3

Assumptions:

peer device is BT2.1 (supporting secure simple pairing)

at least one device with security level = 3 (MITM protection / authentication enabled)

the pairing initiating device is aware of the peer device's Bluetooth Device Address

Remarks:

Connections with BT2.1 are always encrypted

"MITM" = Man-In-The-Middle. "MITM protection" means "protection against a MITM attack".

MITM protection is equivalent with authentication

Figure 3:  BTM vs BTM, security level 3

Figure 4: BTM vs PC, security level 3

On the Laird BTM51x, certain profiles can be used simultaneously (with restrictions) for various use cases. For example, A2DP (stereo audio) can be used at the same time as AVRCP (remote control) so that a Bluetooth speaker (audio sink) can control the music player (audio source) while streaming music.

The following are a few examples of simultaneous profile scenarios on the BTM51x.

1. A2DP, AVRCP, and SPP with one device

Note: A2DP is the Advanced Audio Distribution Profile. AVRCP is the Audio / Video Remote Control Profile. SPP is the Serial Port Profile.

2. A2DP, AVRCP, and SPP with two devices (any combination is possible)

3. A2DP, AVRCP, and SPP with three devices

Use of the LC3 codec is included in the Bluetooth product licence when you qualify your product. No additional licence fees are required.