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Music Shield User Manual
Audio output: The I2S pins and earphone are used for audio output from VS1053. The
LEFT/RIGHT pads are used for Left/Right channel output. The GBUF pad is used for Common buffer for
headphones. The I2S output pins (LOROUT, MCLK, SCLK, SDTA) are retained on the Music shield.
Recording: MICP/MICN, the differential mic input; LINE1/LINE2, the Line-in 1/2. The mic on
Music Shield is connected to MICP/MICN and the earphone is connected to LINE2.
Note: please refer to the section Packages and Pin Descriptions of VS1053b datasheet.
2.2. Serial Protocol for Serial Command Interface (SCI)
The serial bus protocol for the Serial Command Interface SCI (Chapter 8.6) consists of an
instruction byte, address byte and one 16-bit data word. Each read or write operation can read or
write a single register. Data bits are read at the rising edge, so the user should update data at the
falling edge. Bytes are always send MSb first. XCS should be low for the full duration of the operation.
The operation is specified by an 8-bit instruction opcode. The supported instructions are read
and write. See table below.
SCI Read
XCS
0
1
2
SCK
SI
0
0
0
instruction (read)
SO
0
0
0
DREQ
VS1053b registers are read from using the following sequence. First, XCS line is pulled low to
select the device. Then the READ opcode (0x3) is transmitted via the SI line followed by an 8-bit word
Revision 1.1. Date: December 7, 2015. Author: W. L. Yan. Editor: Felix.
Instruction
Name
Opcode
READ
0b0000 0011
WRITE
0b0000 0010
3
4
5
6
7
8
9
10 11 12 13
0
0
0
1
1
0
0
0
0
0
0
0
0
0
0
0
(See the Figure 6 of VS1053b datasheet)
Operation
Read data
Write data
14 15 16 17
3
2
1
0
don't care
0
address
15 14
0
0
0
0
0
share awesome hardware
30 31
don't care
data out
1
0
X
execution
3
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