ST X-NUCLEO-AMICAM1 User manual

Introduction
The X-NUCLEO-AMICAM1 expansion board allows synchronized acquisition and streaming of up to 4 microphones at a
maximum sampling rate of 192 KHz.
It represents a quick and easy solution to develop microphone-based applications and start implementing audio algorithms.
The expansion board is designed around the MP23ABS1 analog MEMS microphone and is compatible with the ST morpho
connector layout and with analog microphone coupon boards (e.g., STEVAL-MIC004V1).
The X-NUCLEO-AMICAM1 embeds three MP23ABS1 microphones: two connected to an external ADC and one directly routed
to the STM32 embedded ADC.
The analog amplification stage is achieved thanks to ST TSV91x wide bandwidth operational amplifiers.
Figure 1. X-NUCLEO-AMICAM1 expansion board
Getting started with the X-NUCLEO-AMICAM1 analog MEMS microphone
expansion board based on MP23ABS1 for STM32 Nucleo
UM2649
User manual
UM2649 - Rev 2 - March 2020
For further information contact your local STMicroelectronics sales office.
www.st.com

1Overview
The X-NUCLEO-AMICAM1 expansion board is a comprehensive tool designed for the evaluation of MP23ABS1
analog MEMS microphones.
It features:
•3 on-board MP23ABS1 analog MEMS microphones
• 5 slots to plug analog microphone coupon boards (e.g., STEVAL-MIC004V1)
• Synchronized acquisition and streaming of up to 4 microphones
• Amplification stage based on TSV91x wide bandwidth operational amplifiers
• On-board external ADC
• Direct acquisition of a single microphone exploiting STM32 embedded ADC
• Up to 192 KHz sampling frequency
• Free comprehensive development firmware library and audio capture plus USB streaming sample
application compatible with STM32Cube
• Compatible with STM32 Nucleo boards
• Equipped with ST morpho connectors (top and bottom) and Arduino UNO R3 connectors (top) to allow
stacking of multiple boards
• RoHS and WEEE compliant
The X-NUCLEO-AMICAM1 expansion board implements an amplification stage for each microphone, based on
TSV91x operational amplifiers, and allows microphone recording using either a dedicated third-party external
analog to digital converter, mounted on-board, or the embedded STM32 ADC.
Figure 2. X-NUCLEO-AMICAM1, STM32 Nucleo and STEVAL-MIC004V1 stack
As shown in the figure above, three microphones are mounted on the X-NUCLEO-AMICAM1 expansion board: 2
of them (M1OB, M2OB) are connected to the external ADC while the third one (M3OB) is directly connected to
STM32 embedded ADC.
Five additional headers are available for external analog microphone coupon boards (e.g. STEVAL-MIC004V1).
The external ADC is controlled through a SPI interface.
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Overview
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The expansion board provides also USB streaming using the STM32 Nucleo microcontroller USB peripheral; a
USB connector is available for data and power supply.
Solder bridges allow choosing from different options, depending on the number of microphones and the MCU
peripherals involved.
Figure 3. X-NUCLEO-AMICAM1 expansion board block diagram
High bandwidth Op
MP23ABS1
Microphone
External
Ext MIC
I2S
Analog
TSV91x
Internal
High bandwidth Op
High bandwidth Op
High bandwidth Op
DFSDM Microphone
MP23ABS1
Analog
Microphone
Analog
Analog
Amp
TSV91x
MP23ABS1
High bandwidth Op
ADC
Amp
connector
TSV91x
Amp
TSV91x
Amp
TSV91x
ADC
SPI
USB
Sensing
Connectivity
Amp
Processing Ext MIC
connector
Ext MIC
connector
Ext MIC
connector
Ext MIC
connector
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Overview
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2Hardware description
Two different solutions are implemented on the X-NUCLEO-AMICAM1 expansion board to allow MP23ABS1
evaluation in different scenarios:
• a low power and low cost solution using STM32 embedded ADC and TSV912 operational amplifier
• the use of a third party external ADC and TSV914 amplifier
Acoustic quality, power consumption hardware requirements (power supply and amplification circuits) differ on the
basis of the chosen solution.
2.1 Amplification stage and signal acquisition - internal ADC
The STM32 analog to digital converter is used in single ended configuration: the microphone signal, in this case,
is amplified around a common mode which is equal to half the VREF provided to the STM32 analog supply input
(for further details on the power scheme, see Figure 6. X-NUCLEO-AMICAM1 expansion board: power supply
scheme).
Figure 4. X-NUCLEO-AMICAM1 expansion board: amplification of a single microphone
R1
A2V5
R2
INTREF_BUFF
M1
R3
R4
R5
C1
M1+
INTREF_BUFF (1.25 V)
The first operational amplifier is used as a buffer for the bias signal generated by a voltage divider (with R1 equal
to R2); the second one adds a gain equal to 1 + R4
R3 to the microphone signal which is then routed to the STM32
ADC.
Depending on the STM32 Nucleo development board, different ADC configurations are possible, enabling several
acquisition strategies which may include oversampling, filtering and decimation using DFSDM hardware
peripheral to gain in SNR and bit depth.
2.2 Amplification stage and signal acquisition - external ADC
The adopted third party analog to digital converter has a differential interface: the microphone amplification stage
performs both gain addition and single to differential conversion to exploit the ADC dynamics.
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Hardware description
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Figure 5. X-NUCLEO-AMICAM1 expansion board: amplification and conversion to differential
M1+
M1-
COMM COMM
COMM
M1
R1
R2
R3
R4
R5
C1
The first operational amplifier adds a gain equal to 1 + R2
R1, while the second one, configured in inverting
configuration with R3 equal to R4, simply adds a phase shift of 180 degrees to the amplified signal.
The COMM represents the bias provided by the external ADC, which is controlled by an SPI interface, and
microphone data are acquired by the STM32 through an I²S interface.
2.3 Power scheme
Power scheme is designed to provide separate supplies to the critical analog parts, which you can find on both
the X-NUCLEO-AMICAM1 and the STM32 Nucleo boards.
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Power scheme
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Figure 6. X-NUCLEO-AMICAM1 expansion board: power supply scheme
USB
X-NUCLEO-AMICAM1
U1
3.0 LDO
U5V
E5V
+5V
STM32 NUCLEO
USB
JP5
U4
3V3 LDO
J1
3V3
J2
VREF
U2
2.5 LDO
EXT ADC
All the analog supplies are generated starting from the 3V3 coming from the LDO on the STM32 Nucleo boards.
Starting from this source, two different regulators are used on the X-NUCLEO-AMICAM1 expansion board:
• U1 LDO which outputs 3 volts used by the microphones connected to the external ADC and all the relevant
components
• U2 LDO which generates 2.5 volts and feeds the single microphone connected to the internal STM32 ADC
as well as the STM32 analog reference
Note: in the standard board configuration, the single microphone (M3OB) connected to the STM32 ADC is disabled by
default; to enable this feature two actions are required:
• unsolder a solder bridge on the STM32 Nucleo (the solder bridge depends on the STM32 Nucleo type, as
detailed in Section 3.1.2 Single microphone acquisition configuration)
• close J2 header
Caution: Do not close J2 if the proper solder bridge is not open on the STM32 Nucleo board, as the STM32 Nucleo and
the X-NUCLEO-AMICAM1 expansion board could be damaged (refer to Section 3.1 Board setup for further
information).
The on-board USB connector supports audio streaming to the host PC and can also be used to power the whole
system up, including the STM32 Nucleo board, by:
• closing jumper J1 on the X-NUCLEO-AMICAM1 expansion board
• placing JP5 in position E5 on the STM32 Nucleo development board
2.4 Solder bridges
Solder bridges allow you to choose among different configurations and enable or disable on-board microphones
versus microphone coupon boards.
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Solder bridges
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Table 1. X-NUCLEO-AMICAM1: solder bridge functions
Function Solder bridge
I²S serial data 2 from external ADC SB1
I²S bit clock to external ADC SB2
I²S serial data 1 from external ADC SB3
I²S word select SB4
Amplified single microphones to STM32 ADC pin SB6
NRST signal to external ADC reset pin SB7
NRST signal to external ADC reset pin SB8
Microphone coupon M5 connected to STM32 ADC SB9
On-board microphone M3OB connected to STM32 ADC SB10
I²S master clock to external ADC SB11
SPI CS to external ADC SB12
SPI MOSI to external ADC SB13
SPI MISO from external ADC SB14
SPI clock SB15
I²S bit clock to external ADC SB16
I²S master clock to external ADC SB18
USB DP signal SB19
USB DM signal SB20
I²S serial data 2 from external ADC SB21
I²S bit clock to external ADC SB22
Microphone coupon M1 connected to external ADC SB23
On-board microphone M1OB connected to external ADC SB24
Microphone coupon M2 connected to external ADC SB25
On-board microphone M2OB connected to external ADC SB26
2.5 Connectors
Table 2. X-NUCLEO-AMICAM1 expansion board: ST morpho connectors
Connector Pin Signal Remarks
CN7
1 I2S_CK
2 I2S_SD2
3 I2S_SD1
4 NRST
6 E5V
8 GND
12 3V3
14 NRST
16 3V3
17 I2S_WS
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Connectors
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Connector Pin Signal Remarks
CN7
18 5V
19 GND
20 GND
22 GND
28 M5+
CN10
1 SPI_CS
4 I2S_MCLK
7 A2V5 If J2 is closed
9 GND
11 SPI1_SCK
12 OTG_FS_DP_NUCLEO
13 SPI_MISO
14 OTG_FS_DM_NUCLEO
15 SPI1_MOSI
19 I2S_MCLK
20 GND
25 I2S_CK
26 I2S_SD2
30 I2S_CK
32 AGND
Table 3. X-NUCLEO-AMICAM1 expansion board: Arduino connectors
Connector Pin Signal Remarks
CN6
2 3V3
3 NRST
4 3V3
5 5V
6 GND
7 GND
8 V_IN
CN8 1 M5+
CN5
2 I2S_MCLK
4 SPI_MOSI
5 SPI_MISO
6 SPI_SCK
7 GND
8 A2V5 If J2 is closed
CN9 7 I2S_CK
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Connectors
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3System requirements
To use the X-NUCLEO-AMICAM1 expansion board, you need the same hardware and software resources of
STM32 Nucleo boards (for details, refer to UM1724 on www.st.com) as well as 40 MB of free space on your hard
disk and at least 128 MB of RAM to run the firmware package.
3.1 Board setup
The X-NUCLEO-AMICAM1 expansion board can be connected to any STM32 Nucleo board. However, the related
firmware offers an out-of-the-box package for some STM32 Nucleo boards.
When mounting the X-NUCLEO-AMICAM1 on the STM32 Nucleo, align all the pins with their corresponding
connector.
Caution: Handle the boards carefully during this operation and implement ESD prevention measures to avoid damaging
(or bending) the male/female pins, connectors and the expansion board components.
The default X-NUCLEO-AMICAM1 configuration allows the acquisition of two on-board microphones (M1OB and
M2OB) through the external ADC mounted on the board.
The following configurations and use cases can also be implemented:
• 4 microphone acquisition using coupon boards (e.g. STEVAL-MIC004V1) and the external ADC
• single microphone acquisition using STM32 embedded ADC
3.1.1 4 microphone acquisition configuration
Step 1. Open SB24 and SB26 to disconnect M1OB and M2OB on-board microphones from the ADC
Step 2. Close SB23 and SB25 to connect M1 and M2 external headers to the ADC
Step 3. Mount coupon boards on the headers
Caution: Do not close SB23 and SB24 at the same time to avoid potential shortcircuit between M1OB on-board
microphone and M1 external microphone if the coupon is mounted.
Do not close SB25 and SB26 at the same time: it will result in a potential shortcut between M2OB onboard
microphone and M2 external microphone if the coupon is mounted.
3.1.2 Single microphone acquisition configuration
Step 1. Change the solder bridge configuration on the STM32 Nucleo to allow VREF routing to the appropriate
STM32 pin as follows:
–On STM32 Nucleo-XXXXRX 64-pin boards (MB1136): open SB57
– On STM32 Nucleo-LXXXZX 144-pin boards (MB1312): open SB149, close SB 119
– On STM32 Nucleo-XXXXZX 144-pin boards (MB1137): open SB12
Step 2. Close J2 on the X-NUCLEO-AMICAM1 board.
Caution: Do not close J2 if the proper solder bridge is not open on the STM32 Nucleo board, as the STM32 Nucleo and
the X-NUCLEO-AMICAM1 expansion board could be damaged.
Step 3. Check SB9 and SB10 on the X-NUCLEO-AMICAM1.
– SB10 closed, SB9 open: acquisition of the on-board M3OB microphone
– SB10 open, SB9 closed: acquisition of an external coupon plugged onto M5 header
Caution: Do not close SB9 and SB10 at the same time as a potential shortcircuit could occur between M3OB on-board
microphone and M5 external microphone if the coupon board is mounted.
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System requirements
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4Bill of materials
Table 4. X-NUCLEO-AMICAM1 bill of materials
Item Q.ty Ref. Part / Value Description Manufacturer Order code
1 1 CN5 HEADER 10 Arduino connector Samtec or
equivalent SSQ-110-21-F-S
2 2 CN6, CN9 HEADER 8 Arduino connectors Samtec or
equivalent SSQ-108-21-F-S
3 2 CN7, CN10 HEADER 19x2 Morpho connectors Samtec or
equivalent SSQ-119-01-L-D
4 1 CN8 HEADER 6 Arduino connector Samtec or
equivalent SSQ-106-21-F-S
5 20
C1, C2, C4, C5,
C8, C11, C12, C13,
C19, C22, C25,
C28, C33, C35,
C37, C38, C39,
C40, C43, C44
1 µF X5R ±10%
0402 (1005 Metric) Ceramic capacitors Kemet C0402C105K8PAC7411
6 11
C3, C14, C15, C16,
C17, C18, C24,
C31, C34, C41,
C42
100 nF 16 V X7R
±10% 0402 (1005
Metric)
Ceramic capacitors Kemet C0402C104K4RAC7411
7 8
C6, C7, C9, C10,
C26, C29, C30,
C32
10 nF 16 V X7R
±10% 0402 (1005
Metric)
Ceramic capacitors
(not mounted) Yageo CC0402KRX7R7BB103
8 1 C20
39 nF 25 V X7R
±10% 0402 (1005
Metric)
Ceramic capacitor Murata GRM155R71E393KA88D
9 1 C21
47 µF 10 V X5R
±20% 0805 (2012
Metric)
Ceramic capacitor Taiyo Yuden LMK212BBJ476MG-T
10 1 C23
2.2 nF 16 V X7R
±10% 0402 (1005
Metric)
Ceramic capacitor Wurth Elektronik 885000000000
11 1 C27
10 µF 10 V X5R
±10% 0805 (2012
Metric)
Ceramic capacitor Samsung Electro-
MechanicsMurata CL21A106KPFNNNG
12 1 C36
10 nF 16 V X7R
±10% 0402 (1005
Metric)
Ceramic capacitor Yageo CC0402KRX7R7BB103
13 1 D1 ESDA7P60-1U1M High junction
temperature Transil ST ESDA7P60-1U1M
14 1 D2 STPS160A Schottky diode ST STPS160A
15 2 J1, J2 HEADER 2 Stripline TH 2 pin Harwin M20-9773646
16 3 M1OB, M2OB,
M3OB MP23ABS1
High performance
MEMS audio
sensor single
ended analog
bottom-port
microphone
ST MP23ABS1TR
17 5 M1, M2, M3, M4,
M5 HEADER 3X2 Analog microphone coupon connector
Fischer Elektronik
or equivalent BL1/36Z
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Bill of materials
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