2.1 Operation with External MCU

The BM20/23 stereo module supports a UART command set to make an external MCU control the module. The following figure illustrates the interface between the BM20/23 module and an external MCU.

Figure 2-1. Interface Between MCU and BM20/23 Module

The MCU controls the module by the UART interface and wakes up the module by the PWR pin. The stereo module provides a wake-up MCU function that connects to P0_0 pin of the module.

Refer to the UART Command Set document for a list of functions the BM20/23 module supports and how to use the UI tool to configure the UART and UART Command Set tool.

For a more detailed description, refer to the UART_CommandSet_v154 document and the IS20XXS_UI tool. A UART control signal timing sequence is illustrated in the following figure.

Figure 2-2. Power ON/OFF Sequence

A timing sequence of RX indication after power-on is illustrated in the following figure.

Figure 2-3. Timing Sequence of RX Indication After Power-On

A timing sequence of RX indication after power-off is illustrated in the following figure.

Figure 2-4. Timing Sequence of RX Indication After Power-Off

A timing sequence of power-on (Nack) is illustrated in the following figure.

Figure 2-5. Timing Sequence of Power-On (Nack)

If the module is hanged, the reset timing sequence must be as illustrated in the following figure.

Figure 2-6. Reset Timing Sequence if Module is Hanged

If the MCU sends a UART Command and Bluetooth does not respond within X-ms, then the MCU sends a reset signal to BT to perform the hardware reset.

A timing sequence of power drop protection is illustrated in the following figure.

Figure 2-7. Timing Sequence of Power Drop Protection

If the Bluetooth BAT uses an adapter that translates voltage by LDO, it is recommended to use “Reset IC” to avoid power-off suddenly. The Rest IC output pin must be “Open Drain” with a delay time ≦ 10 ms and the recommended part is TCM809SVNB713 or G691L263T73.