ESP32-LyraT V4.3 Hardware Reference

This guide provides functional descriptions, configuration options for ESP32-LyraT V4.3 audio development board. As an introduction to functionality and using the LyraT, please see ESP32-LyraT V4.3 Getting Started Guide. Check section Other Versions of LyraT if you have different version of the board.

In this Section

Overview 

The ESP32-LyraT development board is a hardware platform designed for the dual-core ESP32 audio applications, e.g., Wi-Fi or BT audio speakers, speech-based remote controllers, smart-home appliances with audio functionality(ies), etc.

The block diagram below presents main components of the ESP32-LyraT.

ESP32 LyraT V4.3 Electrical Block Diagram — ESP32-LyraT V4.3 Electrical Block Diagram

Functional Description 

The following list and figure describe key components, interfaces and controls of the ESP32-LyraT board.

ESP32-WROVER-E Module: The ESP32-WROVER-E module contains ESP32 chip to provide Wi-Fi / Bluetooth connectivity and data processing power as well as integrates 4 MB external SPI flash and an additional 8 MB PSRAM for flexible data storage.
Green LED: A general purpose LED controlled by the ESP32-WROVER-E Module to indicate certain operation states of the audio application using dedicated API.
Function DIP Switch: Used to configure function of GPIO12 to GPIO15 pins that are shared between devices, primarily between JTAG Header and MicroSD Card. By default, the MicroSD Card is enabled with all switches in OFF position. To enable the JTAG Header instead, switches in positions 3, 4, 5 and 6 should be put ON. If JTAG is not used and MicroSD Card is operated in the one-line mode, then GPIO12 and GPIO13 may be assigned to other functions. Please refer to ESP32 LyraT V4.3 schematic for more details.
JTAG Header: Provides access to the JTAG interface of ESP32-WROVER-E Module. It may be used for debugging, application upload, as well as implementing several other functions, e.g., Application Level Tracing. See JTAG Header / JP7 for pinout details. Before using JTAG signals to the header, Function DIP Switch should be enabled. Please note that when JTAG is in operation, MicroSD Card cannot be used and should be disconnected because some of JTAG signals are shared by both devices.
UART Header: Serial port: provides access to the serial TX/RX signals between ESP32-WROVER-E Module and USB-UART Bridge Chip.
I2C Header: Provides access to the I2C interface. Both ESP32-WROVER-E Module and Audio Codec Chip are connected to this interface. See I2C Header / JP5 for pinout details.
MicroSD Slot: The development board supports a MicroSD card in SPI/1-bit/4-bit modes, and can store or play audio files in the MicroSD card. Note that JTAG cannot be used and should be disconnected by setting Function DIP Switch when MicroSD Card is in operation, because some of signals are shared by both devices.
I2S Header: Provides access to the I2S interface. Both ESP32-WROVER-E Module and Audio Codec Chip are connected to this interface. See I2S Header / JP4 for pinout details.
Left Microphone: Onboard microphone connected to IN1 of the Audio Codec Chip.
AUX Input: Auxiliary input socket connected to IN2 (left and right channel) of the Audio Codec Chip. Use a 3.5 mm stereo jack to connect to this socket.
Headphone Output: Output socket to connect headphones with a 3.5 mm stereo jack.

Note

The socket may be used with mobile phone headsets and is compatible with OMPT standard headsets only. It does work with CTIA headsets. Please refer to Phone connector (audio) on Wikipedia.

ESP32 LyraT V4.3 Board Layout — ESP32-LyraT V4.3 Board Layout

Right Microphone: Onboard microphone connected to IN1 of the Audio Codec Chip.
Left Speaker Output: Output socket to connect a speaker. The 4-ohm and 3-watt speaker is recommended. The pins have a 2.00 mm / 0.08” pitch.
Right Speaker Output: Output socket to connect a speaker. The 4-ohm and 3-watt speaker is recommended. The pins have a 2.00 mm / 0.08” pitch.
PA Chip: A power amplifier used to amplify stereo audio signal from the Audio Codec Chip for driving two speakers.
Boot/Reset Press Keys: Boot button: holding down the Boot button and momentarily pressing the Reset button to initiate the firmware download mode. Then you can download firmware through the serial port. Reset button: pressing this button alone resets the system.
Touch Pad Buttons: Four touch pads labeled Play, Sel, Vol+ and Vol-. They are routed to ESP32-WROVER-E Module and intended for development and testing of a UI for audio applications using dedicated API.
Audio Codec Chip: The Audio Codec Chip, ES8388, is a low power stereo audio codec with a headphone amplifier. It consists of 2-channel ADC, 2-channel DAC, microphone amplifier, headphone amplifier, digital sound effects, analog mixing and gain functions. It is interfaced with ESP32-WROVER-E Module over I2S and I2S buses to provide audio processing in hardware independently from the audio application.
Automatic Upload: Install three jumpers on this header to enable automatic loading of application to the ESP32. Install all jumpers together on all three headers. Remove all jumpers after upload is complete.
Function Press Keys: Two key labeled Rec and Mode. They are routed to ESP32-WROVER-E Module and intended for developing and testing a UI for audio applications using dedicated API.
USB-UART Bridge Chip: A single chip USB-UART bridge provides up to 1 Mbps transfers rate.
USB-UART Port: Functions as the communication interface between a PC and the ESP32 module.
USB Power Port: Provides the power supply for the board.
Standby / Charging LEDs: The Standby green LED indicates that power has been applied to the Micro USB Port. The Charging red LED indicates that a battery connected to the Battery Socket is being charged.
Battery Socket: Two pins socket to connect a single cell Li-ion battery.

Note

Please verify if polarity on the battery plug matches polarity of the socket as marked on the board’s soldermask besides the socket.
Battery Charger Chip: Constant current & constant voltage linear charger for single cell lithium-ion batteries AP5056. Used for charging of a battery connected to the Battery Socket over the Micro USB Port.
Power On LED: Red LED indicating that Power On Switch is turned on.

Note

The Power On Switch does not affect / disconnect the Li-ion battery charging.
Power Switch: Power on/off knob: toggling it to the left powers the board on; toggling it to the right powers the board off.

Hardware Setup Options 

There are a couple of options to change the hardware configuration of the ESP32-LyraT board. The options are selectable with the Function DIP Switch.

Enable MicroSD Card in 1-wire Mode 

DIP SW	Position
1	OFF
2	OFF
3	OFF
4	OFF
5	OFF
6	OFF
7	OFF ¹
8	n/a

AUX Input detection may be enabled by toggling the DIP SW 7 ON. Note that the AUX Input signal pin should not be be plugged in when the system powers up. Otherwise the ESP32 may not be able to boot correctly.

In this mode:

JTAG functionality is not available
Vol- touch button is available for use with the API

Enable MicroSD Card in 4-wire Mode 

DIP SW	Position
1	ON
2	ON
3	OFF
4	OFF
5	OFF
6	OFF
7	OFF
8	n/a

In this mode:

JTAG functionality is not available
Vol- touch button is not available for use with the API
AUX Input detection from the API is not available

Enable JTAG 

DIP SW	Position
1	OFF
2	OFF
3	ON
4	ON
5	ON
6	ON
7	ON
8	n/a

In this mode:

MicroSD Card functionality is not available, remove the card from the slot
Vol- touch button is not available for use with the API
AUX Input detection from the API is not available

Using Automatic Upload 

Entering of the ESP32 into upload mode may be done in two ways:

Manually by pressing both Boot and RST keys and then releasing first RST and then Boot key.
Automatically by software performing the upload. The software is using DTR and RTS signals of the serial interface to control states of EN, IO0 and IO2 pins of the ESP32. This functionality is enabled by installing jumpers in three headers JP23, JP24 and JP25. For details see ESP32 LyraT V4.3 schematic. Remove all jumpers after upload is complete.

Allocation of ESP32 Pins 

Several pins ESP32 module are allocated to the on board hardware. Some of them, like GPIO0 or GPIO2, have multiple functions. Please refer to the table below or ESP32 LyraT V4.3 schematic for specific details.

GPIO Pin	Type	Function Definition
SENSOR_VP	I	Audio Rec (PB)
SENSOR_VN	I	Audio Mode (PB)
IO32	I/O	Audio Set (TP)
IO33	I/O	Audio Play (TP)
IO27	I/O	Audio Vol+ (TP)
IO13	I/O	JTAG MTCK, MicroSD D3, Audio Vol- (TP)
IO14	I/O	JTAG MTMS, MicroSD CLK
IO12	I/O	JTAG MTDI, MicroSD D2, Aux signal detect
IO15	I/O	JTAG MTDO, MicroSD CMD
IO2	I/O	Automatic Upload, MicroSD D0
IO4	I/O	MicroSD D1
IO34	I	MicroSD insert detect
IO0	I/O	Automatic Upload, I2S MCLK
IO5	I/O	I2S SCLK
IO25	I/O	I2S LRCK
IO26	I/O	I2S DSDIN
IO35	I	I2S ASDOUT
IO19	I/O	Headphone jack insert detect
IO22	I/O	Green LED indicator
IO21	I/O	PA Enable output
IO18	I/O	I2C SDA
IO23	I/O	I2C SCL

(TP) - touch pad
(PB) - push button

Pinout of Extension Headers 

There are several pin headers available to connect external components, check the state of particular signal bus or debug operation of ESP32. Note that some signals are shared, see section Allocation of ESP32 Pins for details.

UART Header / JP2 

	Header Pin
1	3.3V
2	TX
3	RX
4	GND

I2S Header / JP4 

	I2C Header Pin	ESP32 Pin
1	MCLK	GPI0
2	SCLK	GPIO5
1	LRCK	GPIO25
2	DSDIN	GPIO26
3	ASDOUT	GPIO35
3	GND	GND

I2C Header / JP5 

	I2C Header Pin	ESP32 Pin
1	SCL	GPIO23
2	SDA	GPIO18
3	GND	GND

JTAG Header / JP7 

	ESP32 Pin	JTAG Signal
1	MTDO / GPIO15	TDO
2	MTCK / GPIO13	TCK
3	MTDI / GPIO12	TDI
4	MTMS / GPIO14	TMS

Notes of Power Distribution 

The board features quite extensive power distribution system. It provides independent power supplies to all critical components. This should reduce noise in the audio signal from digital components and improve overall performance of the components.

Power Supply Separation 

The main power supply is 5V and provided by a USB. The secondary power supply is 3.7V and provided by an optional battery. The USB power itself is fed with a dedicated cable, separate from a USB cable used for an application upload. To further reduce noise from the USB, the battery may be used instead of the USB.

Three Dedicated LDOs 

ESP32 Module

To provide enough current the ESP32, the development board adopts LD1117S33CTR LDO capable to supply the maximum output current of 800mA.

MicroSD Card and Audio Codec

Two separate LDOs are provided for the MicorSD Card and the Audio Codec. Both circuits have similar design that includes an inductor and double decoupling capacitors on both the input and output of the LDO.

ESP32 LyraT V4.3 - Dedicated LDO for the MicroSD Card

Separate Power Feed for the PAs 

The audio amplifier unit features two NS4150 that require a large power supply for driving external speakers with the maximum output power of 3W. The power is supplied directly to both PAs from the battery or the USB. The development board adds a set of LC circuits at the front of the PA power supply, where L uses 1.5A magnetic beads and C uses 10uF aluminum electrolytic capacitors, to effectively filter out power crosstalk.

ESP32 LyraT V4.3 - Power Supply for the PAs

Selecting of the Audio Output 

The development board uses two mono Class D amplifier ICs, model number NS4150 with maximum output power of 3W and operating voltage from 3.0V to 5.25V.

The audio input source is the digital-to-analog converter (DAC) output of the ES8388. Audio output supports two external speakers.

An optional audio output is a pair of headphones feed from the same DACs as the amplifier ICs.

To switch between using headphones and speakers, the board provides a digital input signal to detect when a headphone jack is inserted and a digital output signal to enable or disable the amplifier ICs. In other words selection between speakers and headphones is under software control instead of using mechanical contacts that would disconnect speakers once a headphone jack is inserted.

Other Versions of LyraT 

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