A great option for applications that require connectivity redundancy, since with this ESP32 you can establish connections via Bluetooth, Wifi or 2G GSM / GPRS networks. With USB-C connector and a boost converter that will control the power and battery charge managed by the integrated IP5306 with controllable behavior through I2C

Hardware Specifications

• Chipset:ESPRESSIF-ESP32 240MHz Xtensa® single-/dual-core 32-bit LX6 microprocessor
• FLASH:QSPI flash 4MB / PSRAM 8MB
• SRAM : 520kB SRAM
• Button Reset
• USB to TTL：CP2104
• Modular interface：UART、SPI、SDIO、I2C、LED PWM、TV PWM、I2S、IRGPIO、capacitor touch sensor, ADC, DACLNA pre-amplifier
• On-board clock：40MHz crystal oscillator
• Working voltage ：2.7V-3.6V
• Working current :About 70mA
• Sleep current: About 1.1mA
• SIM card: Only supports Nano SIM card
• Working temperature range:-40℃ ~ +85℃
• Size&Weight:78.83mm28.92mm8.06mm(11.77g)

Power Supply Specifications

• Power Supply: USB 5V/1A
• Charging current:500mA
• Battery:3.7V lithium battery
• JST Connector:2Pin 1.25mm
• USB: Type-C

Wi-Fi

• Standard: FCC/CE-RED/IC/TELEC/KCC/SRRC/NCC(esp32 chip)
• Protocol:802.11 b/g/n(802.11n，speed up to150Mbps)A-MPDU and A-MSDU polymerization support 0.4μS Protection interval
• Frequency range:2.4GHz~2.5GHz(2400M~2483.5M)
• Transmit Power:22dBm
• Communication distance:300m

GPRS

Band: quad-band GSM/GPRS

Frequency: GSM850MHz, EGSM900MHz, DCS1800MHz and PCS1900MHz

Transmitting power: 

• Class 4 (2W) at GSM 850 and EGSM 900 z
• Class 1 (1W) at DCS 1800 and PCS 1900

GPRS connectivity: GPRS multi-slot class 12（default）

Bluetooth

• Protocol: meet bluetooth v4.2BR/EDR and BLE standard
• Radio frequency with -97dBm sensitivity NZIF receiver Class-1,Class-2&Class-3 emitter AFH Audio frequency CVSD&SBC audio frequency

Software specification

• Wi-Fi Mode: Station/SoftAP/SoftAP+Station/P2P
• Security mechanism :WPA/WPA2/WPA2-Enterprise/WPS
• Encryption Type: AES/RSA/ECC/SHA
• Firmware upgrade UART download/OTA Through network/host to download and write firmware）
• Software Development Support cloud server development /SDK for user firmware development
• Networking protocol：IPv4、IPv6、SSL、TCP/UDP/HTTP/FTP/MQTT
• User Configuration AT + Instruction set, cloud server, android/iOSapp

Pinout Description

// TTGO T-Call pins
#define MODEM_RST            5
#define MODEM_PWKEY          4
#define MODEM_POWER_ON       23
#define MODEM_TX             27
#define MODEM_RX             26
#define I2C_SDA              21
#define I2C_SCL              22

Recommended Libraries: https://github.com/vshymanskyy/TinyGSM

Basic Usage examples: https://github.com/CRCibernetica/TTGO-T-Call-Examples

Advanced examples: https://github.com/Xinyuan-LilyGO/LilyGo-T-Call-SIM800/tree/master/examples