User's Manual
The above schematic shows a typical application of BC865RPA module with PIOs running at 1.8v. Double click
on the diagram to see the detail drawings.
Power supply
The whole module shall be powered by a single cell 3.7v Li-ion rechargeable battery (VBAT, pin#34). A coupling
capacitor of 2.2uF should be placed as close to this pin as possible. The module will output 1.8v at VPAD (pin #9). All
PIO pins, SPI programming port and UART port will run at this power rail.
Differential Audio Outputs
The output stage digital circuitry converts the signal from 16-bit per sample, linear PCM of variable sampling frequency to
bit stream, which is fed into the analogue output circuitry. The output stage circuit comprises a DAC with gain setting and class AB
output stage amplifier. The output is available as a differential signal between SPK_LN and SPK_LP for the left channel, as the
schematic shows, and between SPK_RN and SPK_RP for the right channel. The output stage is capable of driving a speaker directly
when its impedance is at least 8Ω.
UART Port
BC865RPA has a standard UART serial interface that provides a simple mechanism for communicating with other serial
devices using the RS232 protocol. A typical application will be connecting to an external HCI host. When BC865RPA is connected
to another digital device, RX and TX transfer data between the 2 devices. UART configuration parameters, such as baud rate and
packet format, are set by configuration of the BC8645 ROM chip.
To communicate with the UART at its maximum data rate using a standard PC, an accelerated serial port adapter card is required for
the PC.
Possible UART Settings
Parameter Possible values
Minimum 1200 baud (≤2%Error) Baud rate
Maximum 9600 baud (≤1%Error)
Parity None, Odd or Even
Number of stop bits 1 or 2
Bits per byte 8
SPI Programming Port
The SPI is used to program and configure the ROM firmware inside BC8645 chip. It is required in production. Ensure the 4
SPI signals are brought out to either test points or a header. Note that these four signals will run at 1.8v power rail.
Mic Inputs
The microphone bias, MIC_BIAS, provides power to external mic circuitry, and is configurable from 1.8v to 2.4v. The
MIC_BIAS is like any voltage regulator and requires a minimum load to maintain regulation. The MIC_BIAS maintains regulation
within the limits 0.200mA to 1.230mA. The input impedance at MIC_A_N, MIC_A_P, MIC_B_N and MIC_B_P is typically
6.0kΩ
.
LED Drivers
BC865RPA includes 2 pads dedicated to driving LED indicators. Both terminals can be controlled by firmware, The
terminals are open-drain outputs, so the LED must be connected from a positive supply rail to the pad in series with a current
limiting resistor. It is recommended that the LED pad, LED[0] or LED[1] pins, operate with a pad voltage below 0.5V. In this case,
the pad is like a resistor, RON . The resistance together with the external series resistor sets the current in the LED.
Buttons
The example application has assigned the following functions to each PIO pins:
PIN
NAME
Function Descriptions
13
PIO17 REV Select previous song, fast rewind.
29
PIO21
FWD Select next song, fast forward
14
PIO18 PLAY_PAUSE
Play / pause toggle
18
PIO20
VOL- Volume decrease
15
PIO19
VOL+ Volume decrease
33
VBAT_SENSE
BAT_SENSE Battery level detection
39
VREG VREG_EN Power on, sleep mode