Tactile Morse Speech Translator, a ESP32 project

This project builds a wearable Morse code communication system with two independent ESP32-S3 units that communicate wirelessly via ESP-NOW. One unit features a microphone and speaker for audio feedback, while the glove-mounted unit provides tactile Morse input through vibration motors and button controls, allowing users to send and receive messages in real time.

The guide includes a complete parts list for both units, wiring diagrams for the microphone and amplifier circuits, battery charging setup, and step-by-step assembly instructions for mounting the components comfortably. Firmware is provided to handle Morse encoding, wireless pairing, message queuing, and tactile feedback via the vibration motor.

Wiring diagram

Gather all the parts

Qty	Component
1	ESP32-S3 Dev Module (Unit A) The speaker-side ESP32-S3 board that sends audio to the phone and text to the glove.
1	HiLetgo INMP441 I²S Microphone Module Omnidirectional 24-bit I²S MEMS microphone module based on the TDK InvenSense INMP441 IC. Outputs digital audio over a 3-wire I²S bus (SCK/BCLK, WS/LRCLK, SD/DOUT). Supply 1.8–3.3 V; native 3.3 V operation with no level shifting required. L/R channel select pin: tie to GND for left-channel mono output or VDD for right-channel mono output. Use the ESP32 Arduino core or ESP-IDF I2S peripheral API; no separate PlatformIO library is required.
1	MAX98357A I2S Class-D Mono Amplifier Breakout I2S-input Class-D mono audio amplifier IC on a compact breakout board. Accepts I2S digital audio input (BCLK, LRC, DIN) and drives a small speaker or transducer directly. No I2C/SPI control bus is needed. The amplifier supply range is 2.5V-5.5V, and the I2S input pins are compatible with 3.3V logic. SD/MODE controls shutdown and channel selection; GAIN selects 3 dB, 6 dB, 9 dB, 12 dB, or 15 dB gain.
1	8Ω Speaker 28 mm, 8 Ω, 1 W Generic small 8Ω 0.5-3W loudspeaker (~28mm typical). Pair with an I2S amp (MAX98357A) or class-D amp (TPA3116D2) for usable volume; do not drive directly from a GPIO pin. Audio output for music/voice playback.
1	3.7 V 1200 mAh protected LiPo battery The rechargeable battery that powers the speaker-side wearable.
1	Unit A USB-C LiPo charger module with protection The USB-C module that safely charges and protects Unit A's LiPo battery.
1	SPST slide power switch (Unit A) The small slide switch that turns the speaker-side wearable on and off.
1	MCP1700-3302 3.3 V LDO regulator The low-dropout regulator that makes a safe 3.3 V supply from the LiPo battery.
1	3.7 V 500 mAh protected LiPo battery The rechargeable battery that powers the glove wearable.
1	Glove USB-C LiPo charger module with protection The USB-C module that safely charges and protects the glove LiPo battery.
1	SPST slide power switch (glove) The small slide switch that turns the glove unit on and off.
1	MCP1700-3302 3.3 V LDO regulator The low-dropout regulator that makes 3.3 V for the ESP32-C3 from the LiPo battery.
1	10 mm 3 V coin ERM vibration motor — DOT The coin motor on the back of the hand that makes the short Morse dot tap.
1	10 mm 3 V coin ERM vibration motor — DASH The coin motor at the wrist that makes the longer Morse dash tap.
1	AO3400A 30V 5.7A N-channel enhancement-mode logic-level MOSFET in SOT-23-3L. Vgs(th) typically ~0.7V (max 1.45V at Id=250 uA), fully enhanced at Vgs=2.5V-4.5V. RDS(on) ~26 mOhm at Vgs=4.5V, ~38 mOhm at Vgs=2.5V. Driven directly by 3.3V or 5V microcontroller GPIO/PWM as a low-side switch for loads up to its Id and VDS limits. No firmware library required.
1	AO3400A 30V 5.7A N-channel enhancement-mode logic-level MOSFET in SOT-23-3L. Vgs(th) typically ~0.7V (max 1.45V at Id=250 uA), fully enhanced at Vgs=2.5V-4.5V. RDS(on) ~26 mOhm at Vgs=4.5V, ~38 mOhm at Vgs=2.5V. Driven directly by 3.3V or 5V microcontroller GPIO/PWM as a low-side switch for loads up to its Id and VDS limits. No firmware library required.
1	Push Button Yes Momentary push button switch
1	Push Button No Momentary push button switch
1	Push Button Please repeat Momentary push button switch
1	Push Button Thank you Momentary push button switch
1	100 ohm gate resistor — DOT motor 100 Ω The resistor between the ESP32-C3 pin and the DOT motor MOSFET gate.
1	100 ohm gate resistor — DASH motor 100 Ω The resistor between the ESP32-C3 pin and the DASH motor MOSFET gate.
1	100 kilohm gate pulldown — DOT motor 100 kΩ The resistor that keeps the DOT motor off while the ESP32-C3 starts.
1	100 kilohm gate pulldown — DASH motor 100 kΩ The resistor that keeps the DASH motor off while the ESP32-C3 starts.
1	1N5819 flyback diode — DOT motor 1N5819 The diode that safely absorbs the voltage spike from the DOT vibration motor.
1	1N5819 flyback diode — DASH motor 1N5819 The diode that safely absorbs the voltage spike from the DASH vibration motor.
1	1 microfarad ceramic capacitor — Unit A regulator input 1 µF, 6.3 V or higher The capacitor that keeps Unit A's regulator input steady.
1	1 microfarad ceramic capacitor — Unit A regulator output 1 µF, 6.3 V or higher The capacitor that keeps Unit A's 3.3 V supply steady.
1	1 microfarad ceramic capacitor — glove regulator input 1 µF, 6.3 V or higher The capacitor that keeps the glove regulator input steady.
1	1 microfarad ceramic capacitor — glove regulator output 1 µF, 6.3 V or higher The capacitor that keeps the glove 3.3 V supply steady.
1	Unit A USB-C charge socket The USB-C socket where Unit A's charging cable plugs in.
1	Glove USB-C charge socket The USB-C socket where the glove charging cable plugs in.

Assemble it in 5 steps

1. Build the two protected battery supplies

With both switches OFF, connect each LiPo battery BAT+ and BAT− to its own charger B+ and B− pads. Connect charger OUT+ through that unit's slide switch. Send the switched Unit A line to a 3.3 V regulator, and send the switched glove line both to its 3.3 V regulator and to the two motor positive leads.

Never connect a LiPo backwards or charge it without the protection/charger module; reversed battery wiring can overheat or damage the cells.

2. Wire the microphone and speaker unit

Connect Unit A GPIO12 to SCK/BCLK on both audio modules, GPIO13 to WS/LRC on both, INMP441 SD to GPIO14, and GPIO15 to MAX98357A DIN. Connect the microphone L/R pin to GND. Connect MAX98357A SPK+ and SPK− directly to the two speaker tabs; do not connect either speaker tab to ground.

Keep microphone wires short and place the microphone opening away from the speaker to reduce feedback.

3. Build each motor switch

Put each coin motor's negative lead on its AO3400A Drain and the Source on GND. Place a 1N5819 across each motor: striped cathode to motor positive, unstriped anode to the Drain/motor negative. Put a 100 ohm resistor from GPIO3 to the DOT Gate and GPIO4 to the DASH Gate, then place a 100 kilohm resistor from each Gate to GND.

Make sure the striped end of each flyback diode goes to battery positive; reversing it creates a battery short when the motor turns on.

4. Add the glove controls

Connect one side of every tactile button to GND. Connect the other sides to GPIO0 for Yes, GPIO1 for No, GPIO5 for Please repeat, and GPIO6 for Thank you. The firmware turns on each pin's internal pull-up, so no separate button resistor is needed.

5. Mount it comfortably

Sew or bond the DOT motor on the back of the hand and the DASH motor about 3 to 4 cm away at the wrist. Put the C3, drivers, battery, and strain-relieved wires in a soft back-of-hand or wrist pouch. Keep LiPo cells flat, protected from sharp bends, and removable for inspection.

Test motor locations with loose tape before sewing; the two sensations must be easy to tell apart.

Review all connections

1. Connections between "unit_a_s3" and "ESP32"

Function	unit_a_s3	ESP32
`power`	3V3 → MCP1700-3302 3.3 V LDO regulator OUT	EXT
`ground`	GND → Unit A common ground	GND
`digital`	GPIO12_BCLK → HiLetgo INMP441 I²S Microphone Module SCK	EXT
`digital`	GPIO12_BCLK → MAX98357A I2S Class-D Mono Amplifier Breakout BCLK	EXT
`digital`	GPIO13_LRCLK → HiLetgo INMP441 I²S Microphone Module WS	EXT
`digital`	GPIO13_LRCLK → MAX98357A I2S Class-D Mono Amplifier Breakout LRC	EXT
`digital`	GPIO15_AMP_DOUT → MAX98357A I2S Class-D Mono Amplifier Breakout DIN	EXT

2. Connections between "mic" and "ESP32"

Function	mic	ESP32
`data`	SD → ESP32-S3 Dev Module (Unit A) GPIO14_MIC_DIN	EXT
`power`	VDD → ESP32-S3 Dev Module (Unit A) 3V3	EXT
`ground`	GND → Ground	GND
`ground`	L/R → Select left microphone channel	GND

3. Connections between "amp" and "ESP32"

Function	amp	ESP32
`power`	VIN → ESP32-S3 Dev Module (Unit A) 3V3	EXT
`ground`	GND → Ground	GND
`digital`	SD → ESP32-S3 Dev Module (Unit A) 3V3	EXT
`data`	SPK+ → 8Ω Speaker POS	EXT
`data`	SPK- → 8Ω Speaker NEG	EXT

4. Connections between "a_battery" and "ESP32"

Function	a_battery	ESP32
`power`	BAT+ → Unit A USB-C LiPo charger module with protection B+	EXT
`ground`	BAT- → Unit A USB-C LiPo charger module with protection B-	EXT

5. Connections between "a_charger" and "ESP32"

Function	a_charger	ESP32
`ground`	GND → Common ground	GND
`power`	OUT+ → SPST slide power switch (Unit A) IN	EXT
`ground`	OUT- → Protected battery ground	GND

6. Connections between "a_switch" and "ESP32"

Function	a_switch	ESP32
`power`	OUT → MCP1700-3302 3.3 V LDO regulator IN	EXT

7. Connections between "a_regulator" and "ESP32"

Function	a_regulator	ESP32
`ground`	GND → Regulator ground	GND

8. Connections between "a_in_cap" and "ESP32"

Function	a_in_cap	ESP32
`power`	Positive → MCP1700-3302 3.3 V LDO regulator IN	EXT
`ground`	Negative → Ground return	GND

9. Connections between "a_out_cap" and "ESP32"

Function	a_out_cap	ESP32
`power`	Positive → MCP1700-3302 3.3 V LDO regulator OUT	EXT
`ground`	Negative → Ground return	GND

10. Connections between "glove_battery" and "ESP32"

Function	glove_battery	ESP32
`power`	BAT+ → Glove USB-C LiPo charger module with protection B+	EXT
`ground`	BAT- → Glove USB-C LiPo charger module with protection B-	EXT

11. Connections between "glove_charger" and "ESP32"

Function	glove_charger	ESP32
`ground`	GND → Common ground	GND
`power`	OUT+ → SPST slide power switch (glove) IN	EXT
`ground`	OUT- → Protected battery ground	GND

12. Connections between "glove_switch" and "ESP32"

Function	glove_switch	ESP32
`power`	OUT → MCP1700-3302 3.3 V LDO regulator IN	EXT
`power`	OUT → 10 mm 3 V coin ERM vibration motor — DOT M+	EXT
`power`	OUT → 10 mm 3 V coin ERM vibration motor — DASH M+	EXT

13. Connections between "glove_regulator" and "ESP32"

Function	glove_regulator	ESP32
`power`	OUT → ESP32-C3 regulated power	3V3
`ground`	GND → Regulator ground	GND

14. Connections between "g_in_cap" and "ESP32"

Function	g_in_cap	ESP32
`power`	Positive → MCP1700-3302 3.3 V LDO regulator IN	EXT
`ground`	Negative → Ground return	GND

15. Connections between "g_out_cap" and "ESP32"

Function	g_out_cap	ESP32
`power`	Positive → Output stabilizer	3V3
`ground`	Negative → Ground return	GND

16. Connections between "motor_dot" and "ESP32"

Function	motor_dot	ESP32
`power`	M- → AO3400A Drain (D)	EXT

17. Connections between "motor_dash" and "ESP32"

Function	motor_dash	ESP32
`power`	M- → AO3400A Drain (D)	EXT

18. Connections between "fet_dot" and "ESP32"

Function	fet_dot	ESP32
`ground`	Source (S) → Ground return	GND

19. Connections between "fet_dash" and "ESP32"

Function	fet_dash	ESP32
`ground`	Source (S) → Ground return	GND

20. Connections between "dot_diode" and "ESP32"

Function	dot_diode	ESP32
`power`	Anode → AO3400A Drain (D)	EXT
`power`	Cathode → 10 mm 3 V coin ERM vibration motor — DOT M+	EXT

21. Connections between "dash_diode" and "ESP32"

Function	dash_diode	ESP32
`power`	Anode → AO3400A Drain (D)	EXT
`power`	Cathode → 10 mm 3 V coin ERM vibration motor — DASH M+	EXT

22. Connections between "dot_gate_r" and "ESP32"

Function	dot_gate_r	ESP32
`digital`	A → DOT PWM signal	GPIO 3
`digital`	B → AO3400A Gate (G)	EXT

23. Connections between "dash_gate_r" and "ESP32"

Function	dash_gate_r	ESP32
`digital`	A → DASH PWM signal	GPIO 4
`digital`	B → AO3400A Gate (G)	EXT

24. Connections between "dot_pulldown" and "ESP32"

Function	dot_pulldown	ESP32
`digital`	A → AO3400A Gate (G)	EXT
`ground`	B → Ground return	GND

25. Connections between "dash_pulldown" and "ESP32"

Function	dash_pulldown	ESP32
`digital`	A → AO3400A Gate (G)	EXT
`ground`	B → Ground return	GND

26. Connections between "button_yes" and "ESP32"

Function	button_yes	ESP32
`ground`	GND → Ground return	GND
`digital`	SIGNAL → Yes reply input	GPIO 0

27. Connections between "button_no" and "ESP32"

Function	button_no	ESP32
`ground`	GND → Ground return	GND
`digital`	SIGNAL → No reply input	GPIO 1

28. Connections between "button_repeat" and "ESP32"

Function	button_repeat	ESP32
`ground`	GND → Repeat reply input	GND
`digital`	SIGNAL → Please repeat reply input	GPIO 5

29. Connections between "button_thanks" and "ESP32"

Function	button_thanks	ESP32
`ground`	GND → Ground return	GND
`digital`	SIGNAL → Thank you reply input	GPIO 6

30. Connections between "a_charge_port" and "ESP32"

Function	a_charge_port	ESP32
`power`	5V → Unit A USB-C LiPo charger module with protection USB-C 5V	EXT
`ground`	GND → USB ground	GND

31. Connections between "g_charge_port" and "ESP32"

Function	g_charge_port	ESP32
`power`	5V → Glove USB-C LiPo charger module with protection USB-C 5V	EXT
`ground`	GND → USB ground	GND

Deploy the firmware

main.cppOpen in Schematik

#include <Arduino.h>
#include <WiFi.h>
#include <esp_now.h>
#include <esp_wifi.h>

#define DOT_PIN 3
#define DASH_PIN 4
#define YES_PIN 0
#define NO_PIN 1
#define REPEAT_PIN 5
#define THANKS_PIN 6
constexpr uint8_t ESPNOW_CHANNEL=6, QUEUE_SIZE=192;
enum Kind:uint8_t{HELLO=1,TEXT=2,ACK=3,REPLY=4};
struct __attribute__((packed)) Packet { uint8_t kind; uint16_t seq; uint8_t len; char text[200]; };
char q[QUEUE_SIZE]; uint8_t head=0,tail=0; bool active=false,dash=false; uint32_t nextAt=0; uint16_t dotMs=120,lastSeq=0; bool keywordsOnly=false; uint8_t peer[6]; bool paired=false;
const char* morse(char c){ switch(c){case 'A':return ".-";case 'B':return "-...";case 'C':return "-.-.";case 'D':return "-..";case 'E':return ".";case 'F':return "..-.";case 'G':return "--.";case 'H':return "....";case 'I':return "..";case 'J':return ".---";case 'K':return "-.-";case 'L':return ".-..";case 'M':return "--";case 'N':return "-.";case 'O':return "---";case 'P':return ".--.";case 'Q':return "--.-";case 'R':return ".-.";case 'S':return "...";case 'T':return "-";case 'U':return "..-";case 'V':return "...-";case 'W':return ".--";case 'X':return "-..-";case 'Y':return "-.--";case 'Z':return "--..";case '0':return "-----";case '1':return ".----";case '2':return "..---";case '3':return "...--";case '4':return "....-";case '5':return ".....";case '6':return "-....";case '7':return "--...";case '8':return "---..";case '9':return "----.";case '.':return ".-.-.-";case ',':return "--..--";case '?':return "..--..";case '/':return "-..-.";case '-':return "-....-";default:return "";} }
void push(char c){uint8_t n=(head+1)%QUEUE_SIZE;if(n==tail)tail=(tail+1)%QUEUE_SIZE;q[head]=c;head=n;}
bool pop(char &c){if(tail==head)return false;c=q[tail];tail=(tail+1)%QUEUE_SIZE;return true;}
void sendPacket(uint8_t kind,uint16_t seq,const char* text=""){if(!paired)return;Packet p={};p.kind=kind;p.seq=seq;p.len=min((size_t)200,strlen(text));memcpy(p.text,text,p.len);esp_now_send(peer,(uint8_t*)&p,sizeof(p.kind)+sizeof(p.seq)+sizeof(p.len)+p.len);}
void onRecv(const esp_now_recv_info_t* info,const uint8_t* data,int len){if(len<4)return;Packet p={};memcpy(&p,data,min(len,(int)sizeof(p)));memcpy(peer,info->src_addr,6);paired=true;if(p.kind==TEXT){sendPacket(ACK,p.seq);if(p.seq==lastSeq)return;lastSeq=p.seq;for(uint8_t i=0;i<p.len;i++){char c=toupper((unsigned char)p.text[i]);if(!keywordsOnly || strchr(" YESNOHELPSTOPREPEATTHANKYOU",c))push(c);}}}
void schedule(){static const char* symbols="";static uint8_t i=0;uint32_t now=millis();if(now<nextAt)return;if(active){ledcWrite(DOT_PIN,0);ledcWrite(DASH_PIN,0);active=false;nextAt=now+dotMs;return;}if(symbols&&symbols[i]){dash=symbols[i++]== '-';ledcWrite(dash?DASH_PIN:DOT_PIN,180);active=true;nextAt=now+(dash?3*dotMs:dotMs);return;}char c; if(!pop(c))return;if(c==' '){nextAt=now+7*dotMs;return;}symbols=morse(c);i=0;if(*symbols)nextAt=now+2*dotMs;}
void buttons(){static uint32_t down[4]={};static bool held[4]={};int pins[4]={YES_PIN,NO_PIN,REPEAT_PIN,THANKS_PIN};for(int i=0;i<4;i++){bool low=!digitalRead(pins[i]);if(low&&!down[i])down[i]=millis();if(low&&down[i]&&!held[i]&&millis()-down[i]>900){held[i]=true;if(i==2){head=tail=0;}if(i==3){dotMs=dotMs==240?80:dotMs+20;}}if(!low&&down[i]){if(!held[i]){const char* r[]={"YES","NO","PLEASE_REPEAT","THANK_YOU"};sendPacket(REPLY,0,r[i]);}down[i]=0;held[i]=false;}}}
void setup(){for(int p:{YES_PIN,NO_PIN,REPEAT_PIN,THANKS_PIN})pinMode(p,INPUT_PULLUP);ledcAttach(DOT_PIN,180,8);ledcAttach(DASH_PIN,180,8);WiFi.mode(WIFI_STA);esp_wifi_set_channel(ESPNOW_CHANNEL,WIFI_SECOND_CHAN_NONE);if(esp_now_init()!=ESP_OK)return;esp_now_register_recv_cb(onRecv);esp_now_peer_info_t b={};memset(b.peer_addr,0xFF,6);b.channel=ESPNOW_CHANNEL;b.ifidx=WIFI_IF_STA;esp_now_add_peer(&b);Packet h={};h.kind=HELLO;esp_now_send(b.peer_addr,(uint8_t*)&h,4);}
void loop(){schedule();buttons();delay(1);}