TTGO T-Call (LilyGO)
ESP32 development board with GSM/GPRS cellular connectivity, supporting SIM800H and A7670E modules for IoT and remote communication projects.
Pinout
24 pins · 2.54 mm pitch
| Pin | GPIO | Labels | Status | Capabilities | Notes |
|---|---|---|---|---|---|
| 1 | 0 | IO0GPIO0 | strapping | - | GPIO0, Boot Mode Selection |
| 2 | 2 | IO2GPIO2 | strapping | - | GPIO2, General Purpose I/O |
| 3 | 4 | IO4GPIO4 | control | - | SIM800L modem PWRKEY (MODEM_PWRKEY); GPIO4 / ADC10 / TOUCH4 on header |
| 4 | 5 | IO5GPIO5 | control | - | SIM800L modem reset (MODEM_RST); GPIO5 / VSPI_SS on header |
| 5 | 12 | IO12GPIO12 | strapping | adc | GPIO12, ADC or GPIO |
| 6 | 13 | IO13GPIO13 | strapping | adc | GPIO13, ADC or GPIO |
| 7 | 14 | IO14GPIO14 | strapping | adc | GPIO14, ADC or GPIO |
| 8 | 15 | IO15GPIO15 | strapping | adc | GPIO15, ADC or GPIO |
| 9 | 16 | IO16GPIO16 | strapping | - | GPIO16, General Purpose I/O |
| 10 | 3 | RXD0GPIO3 | uart | uart | UART0 Receive |
| 11 | 1 | TXD0GPIO1 | uart | uart | UART0 Transmit |
| 12 | 17 | IO17GPIO17 | strapping | - | GPIO17, General Purpose I/O |
| 13 | 18 | IO18GPIO18 | safe | - | GPIO18, General Purpose I/O |
| 14 | 19 | IO19GPIO19 | safe | - | GPIO19, General Purpose I/O |
| 15 | 21 | IO21GPIO21 | safe | i2c | GPIO21, I2C SDA |
| 16 | 22 | IO22GPIO22 | safe | i2c | GPIO22, I2C SCL |
| 17 | 23 | IO23GPIO23 | control | - | SIM800L modem power enable (MODEM_POWER_ON); GPIO23 / VSPI_MOSI on header |
| 18 | 25 | IO25GPIO25 | safe | dac | GPIO25, DAC1 |
| 19 | 26 | IO26GPIO26 | uart | dac · uart | SIM800L modem UART, MODEM_RX define (GPIO26 / DAC2) |
| 20 | 27 | IO27GPIO27 | uart | adc · uart | SIM800L modem UART, MODEM_TX define (GPIO27 / ADC17 / TOUCH7) |
| 21 | 32 | IO32GPIO32 | safe | adc | GPIO32, ADC |
| 22 | 33 | IO33GPIO33 | safe | adc | GPIO33, ADC |
| 23 | 34 | IO34GPIO34 | strapping | adc | GPIO34, ADC Input Only |
| 24 | 35 | IO35GPIO35 | strapping | adc | GPIO35, ADC Input Only |
Start with these
10 pins with no boot or system involvementFreely assignable - no strapping, flash, USB or JTAG duties. Ideal first picks for buttons, sensors and LEDs.
Fine - with a little care
sampled at boot or shared with debug/serial| Pin | Label | What to know | Role |
|---|---|---|---|
| IO0 | GPIO0 | Must be HIGH during boot for normal startup; if held LOW on reset, forces flash programming mode. | Strapping |
| IO2 | GPIO2 | If driven HIGH on reset (while IO0 is LOW), selects an unsupported SDIO boot mode, causing boot failure. | Strapping |
| IO4 | GPIO4 | Sampled at reset for boot config; should not be driven at boot (affects boot mode timing). | Strapping |
| IO5 | GPIO5 | Must be HIGH during boot; if pulled LOW at reset, alters SDIO slave timing and may prevent normal boot. | Strapping |
| IO12 | MTDI (GPIO12) | Keep LOW during boot (internal PD); pulling HIGH at reset selects 1.8V flash mode, causing flash brownout if 3.3V flash is used. | Strapping |
| IO13 | MTCK (GPIO13) | Used for JTAG debugging (TCK); avoid using as GPIO if JTAG is needed. | Other |
| IO14 | MTMS (GPIO14) | Used for JTAG debugging (TMS); driving it as GPIO may interfere with JTAG or produce spurious signals at boot. | Other |
| IO15 | MTDO (GPIO15) | Keep HIGH during boot (internal PU); if LOW on reset, bootloader log is silenced and boot mode may change. | Strapping |
| IO34 | GPIO34 | Cannot be used as output (no drive capability); only suitable for analog/digital input. | Other |
| IO35 | GPIO35 | Cannot be used as output; only suitable for input. | Other |
Only if you know the tricks
wired to flash or USB - expect a fight| Pin | Label | What to know | Role |
|---|---|---|---|
| IO16 | GPIO16 | Connected to internal PSRAM on PSRAM-enabled modules; not usable as GPIO on those modules. | Flash |
| RXD0 | U0RXD (GPIO3) | Used for receiving data from USB-UART (programming); also pulled HIGH at boot for console communication, so using as GPIO can disrupt uploads. | USB |
| TXD0 | U0TXD (GPIO1) | Connected to on-board USB-UART for uploading and logs; drives serial output at boot, so using as GPIO can disrupt programming or console. | USB |
| IO17 | GPIO17 | Connected to internal PSRAM on PSRAM-enabled modules; not usable as GPIO on those modules. | Flash |
Pinout notes Across 24 pins (2.54 mm pitch), the TTGO T-Call (LilyGO) exposes 21 GPIO. On the analog side there are 9 ADC-capable pins for sensors and battery monitoring…
Across 24 pins (2.54 mm pitch), the TTGO T-Call (LilyGO) exposes 21 GPIO.
On the analog side there are 9 ADC-capable pins for sensors and battery monitoring and 2 true DAC outputs.
If you want zero surprises, IO18, IO19, IO21, IO22 and 6 more are free of any such role - the safest first picks. 10 of the exposed pins carry boot-time or system duties on the ESP32 (IO0, IO2, IO4 and 7 more).
The TTGO T-Call pinout provides extensive connectivity options for cellular IoT projects. Power management includes 5V input, 3.3V regulated output, and battery charging circuitry.
Cellular connectivity features dedicated SIM card slot and GSM ANT antenna connector. Communication interfaces include multiple UART channels for cellular module communication, plus standard ESP32 GPIO pins.
GPIO pins support digital I/O, ADC (18 channels), PWM, and multiple protocols. The board includes EN reset button and comprehensive peripheral interfaces for sensor integration and external device connectivity.
Getting started
flash your first firmware in ~2 minutesBoard: Esp32 Dev
Flash Size: 4MB · DIO
Upload Speed: 921600
// blink
pinMode(18, OUTPUT);
digitalWrite(18, LOW); // on (often inverted)[env:ttgo-t-call]
platform = espressif32
board = esp32dev
framework = arduino
monitor_speed = 115200
upload_speed = 921600esp32:
board: esp32dev
variant: esp32
framework:
type: esp-idf
# blink - GPIO18
output:
- platform: gpio
pin: 18
id: led_out
light:
- platform: binary
name: "LED"
output: led_outesptool.py --chip esp32 --port /dev/ttyACM0 \
write_flash 0x0 firmware.binGood to know
board-specific quirks worth 60 seconds
TTGO T-Call Cellular Modules Available Models SIM800H: 2G GSM/GPRS module supporting quad-band GSM (850/900/1800/1900MHz) and GPRS data transmission A7670E: LTE Cat.1 module with global LTE bands, ideal for IoT applications requiring higher data speeds SIM800L: Compact 2G module option for basic cellular connectivity Important Notes The A7670E module has LTE band limitations in some regions (e.g., US LTE…
TTGO T-Call Cellular Modules
Available Models
- SIM800H: 2G GSM/GPRS module supporting quad-band GSM (850/900/1800/1900MHz) and GPRS data transmission
- A7670E: LTE Cat.1 module with global LTE bands, ideal for IoT applications requiring higher data speeds
- SIM800L: Compact 2G module option for basic cellular connectivity
Important Notes
The A7670E module has LTE band limitations in some regions (e.g., US LTE bands may not be fully supported). Check cellular band compatibility for your location. SIM800H provides reliable 2G connectivity but limited data speeds.
Perfect For
Ideal for remote monitoring, asset tracking, smart agriculture, and any IoT project requiring cellular connectivity with WiFi/Bluetooth backup options.
Specifications
ESP32 · 51.52 × 25.04 mmAbout this board
At its core is the ESP32 - a dual-core Xtensa with both Bluetooth Classic and BLE.
Expect to pay about $26.52 - above the ~$20 typical for ESP32 boards.
Onboard you'll find 8MB (QSPI) PSRAM, cellular connectivity (SIM800L), battery charging (IP5306) via JST-PH 2.0 and Reset/Power buttons.
The TTGO T-Call is a powerful ESP32 development board designed for cellular IoT applications, featuring integrated GSM/GPRS connectivity alongside Wi-Fi 802.11 b/g/n and Bluetooth 4.2 + BLE.
Powered by an ESP32 dual-core processor at 240 MHz, with 4MB/8MB flash memory and 8MB PSRAM, it's optimized for demanding IoT projects requiring reliable remote connectivity.
The board features a SIM800L 2G GSM/GPRS modem for cellular communication (sibling T-Call boards use the SIM800H or the 4G A7670E). It includes a nano SIM card slot, GSM antenna connector, and comprehensive cellular interfaces.
Features USB Type-C for programming, Li-Po battery support with charging circuit, and extensive GPIO pins supporting ADC, DAC, PWM, I2C, SPI, UART, I2S, and CAN interfaces. Operating at 3.3V with robust power management.
- Cellular Connectivity
- Li-Po Battery Support
- Nano SIM Slot
- ESP32-WROVER-B with 8MB PSRAM
- u.FL (IPEX) GSM antenna connector
Where to buy
prices are typical street prices
Resources
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