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RoboHeart Hercules
ESP32-powered robotics board with motor drivers and sensor inputs - great for educational robotics kits.
61 × 61 mm
ESP32
MCU
240MHz
clock
4MB
flash
520KB
SRAM
26· 16 ADC
GPIO
BLE 4.2+ WiFi
radio
Pinout
26 pins · 2.54 mm pitch| Pin | GPIO | Labels | Status | Capabilities | Notes |
|---|---|---|---|---|---|
| 1 | 0 | BUTTON_ROBOHEARTG0A11 | strapping | adc | |
| 2 | 1 | G1PWM | uart | - | |
| 3 | 2 | SLEEP_MOTOR_ABCG2A12PWM | strapping | adc | |
| 4 | 3 | G3PWM | uart | - | |
| 5 | 4 | MOTOR_C_IN2A10PWM | strapping | adc | |
| 6 | 5 | SSG5PWM | strapping | spi | |
| 7 | 12 | GSM_PWRKEYG12A15PWM | strapping | adc | |
| 8 | 13 | GSM_DTRG13A14PWM | strapping | adc | |
| 9 | 14 | LED_ROBOHEARTGSM_RTSA16PWM | strapping | adc | |
| 10 | 15 | GSM_CTSG15A13PWM | strapping | adc | |
| 11 | 16 | RXD1RXD2G16PWM | strapping | - | |
| 12 | 17 | TXD1TXD2G17PWM | strapping | - | |
| 13 | 18 | SCKG18PWM | safe | spi | |
| 14 | 19 | MISOG19PWM | safe | spi | |
| 15 | 21 | IMU_SDASDAG21PWM | safe | i2c | |
| 16 | 22 | IMU_SCLSCLG22PWM | safe | i2c | |
| 17 | 23 | MOSIG23PWM | safe | spi | |
| 18 | 25 | MOTOR_A_IN1G25DAC1A18PWM | safe | adc · dac | |
| 19 | 26 | MOTOR_A_IN2G26DAC2A19PWM | safe | adc · dac | |
| 20 | 27 | MOTOR_B_IN1A17PWM | safe | adc | |
| 21 | 32 | MOTOR_B_IN2A4PWM | safe | adc | |
| 22 | 33 | MOTOR_C_IN1A5PWM | safe | adc | |
| 23 | 34 | RXG34A6 | strapping | adc · uart | |
| 24 | 35 | TXG35A7 | strapping | adc · uart | |
| 25 | 36 | BATTERY_PING36A0 | strapping | adc | |
| 26 | 39 | A3 | strapping | adc |
Start with these
10 pins with no boot or system involvementSCKG18MISOG19IMU_SDASDAIMU_SCLSCLMOSIG23MOTOR_A_IN1G25MOTOR_A_IN2G26MOTOR_B_IN1A17MOTOR_B_IN2A4MOTOR_C_IN1A5
Freely 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 |
|---|---|---|---|
| BUTTON_ROBOHEART | GPIO0 | Must be HIGH during boot for normal startup; if held LOW on reset, forces flash programming mode. | Strapping |
| SLEEP_MOTOR_ABC | GPIO2 | If driven HIGH on reset (while IO0 is LOW), selects an unsupported SDIO boot mode, causing boot failure. | Strapping |
| MOTOR_C_IN2 | GPIO4 | Sampled at reset for boot config; should not be driven at boot (affects boot mode timing). | Strapping |
| SS | GPIO5 | Must be HIGH during boot; if pulled LOW at reset, alters SDIO slave timing and may prevent normal boot. | Strapping |
| GSM_PWRKEY | 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 |
| GSM_DTR | MTCK (GPIO13) | Used for JTAG debugging (TCK); avoid using as GPIO if JTAG is needed. | Other |
| LED_ROBOHEART | MTMS (GPIO14) | Used for JTAG debugging (TMS); driving it as GPIO may interfere with JTAG or produce spurious signals at boot. | Other |
| GSM_CTS | MTDO (GPIO15) | Keep HIGH during boot (internal PU); if LOW on reset, bootloader log is silenced and boot mode may change. | Strapping |
| RX | GPIO34 | Cannot be used as output (no drive capability); only suitable for analog/digital input. | Other |
| TX | GPIO35 | Cannot be used as output; only suitable for input. | Other |
| BATTERY_PIN | GPIO36 (SENSOR_VP) | Cannot be used as output; only suitable for input (e.g., analog read). | Other |
| A3 | GPIO39 (SENSOR_VN) | 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 |
|---|---|---|---|
| G1 | 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 |
| G3 | 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 |
| RXD1 | GPIO16 | Connected to internal PSRAM on PSRAM-enabled modules; not usable as GPIO on those modules. | Flash |
| TXD1 | GPIO17 | Connected to internal PSRAM on PSRAM-enabled modules; not usable as GPIO on those modules. | Flash |
These are recommendations, not hard rules - with the right pull-ups, timing and boot-state awareness most pins can be made to work. When in doubt, start green.
Pinout notes The RoboHeart Hercules pinout brings out 26 GPIO pins at a 2.54 mm pitch - every one of them usable in your project. For peripherals, I²C is mapped to SDA on…
The RoboHeart Hercules pinout brings out 26 GPIO pins at a 2.54 mm pitch - every one of them usable in your project.
For peripherals, I²C is mapped to SDA on GPIO21 and SCL on GPIO22; the SPI bus (MOSI, MISO, SCK, SS) is broken out in full; TX/RX on GPIO35 and GPIO34 cover serial logging and flashing.
On the analog side there are 16 ADC-capable pins for sensors and battery monitoring and 2 true DAC outputs.
If you want zero surprises, SCK, MISO, IMU_SDA, IMU_SCL and 6 more are free of any such role - the safest first picks. 12 of the exposed pins carry boot-time or system duties on the ESP32 (BUTTON_ROBOHEART, SLEEP_MOTOR_ABC, MOTOR_C_IN2 and 9 more).
Getting started
flash your first firmware in ~2 minutes1
Connect over USB
Serial chip: onboard. Not detected? Hold BOOT while plugging in.
2
Flash with your tool
Arduino IDE, PlatformIO, ESPHome or esptool - copy the settings on the right.
3
Verify it runs
The blink example uses GPIO18 - swap for your board's LED pin if different.
Board: Roboheart Hercules
Flash Size: 4MB · DIO
Upload Speed: 921600
// blink
pinMode(18, OUTPUT);
digitalWrite(18, LOW); // on (often inverted)[env:roboheart_hercules]
platform = espressif32
board = esp32dev
framework = arduino
monitor_speed = 115200
upload_speed = 921600esp32:
board: esp32dev
variant: roboheart_hercules
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.binBuild details: sketch space 1310720 B · data 327680 B · DIO
Specifications
ESP32 · 61 × 61 mmCompute
MCU
ESP32
Clock
240 MHz
SRAM · Flash
520 KB · 4MB
Radio
Wi-Fi
802.11 b/g/n
Bluetooth
4.2 LE
Antenna
PCB
I/O
GPIO · ADC
26 · 16
UART · I²C · SPI
3 · 2 · 4
PWM
16 channels
Power
USB
USB-C
Serial
-
Boot address
0x1000
Flashing
Upload · OTA
esptool_py · esp_ota
Flash · Boot mode
DIO · DIO
Sketch · Data
1.25 MB · 320 KB
61 × 61 mm · pin pitch 2.54 mm
The RoboHeart Hercules uses esptool_py for firmware uploads, esp_ota for over-the-air (OTA) updates. Flash mode is DIO with DIO boot mode. The maximum sketch size is 1.25 MB with 320 KB available for data.
About this board
At its core is the ESP32 - a dual-core Xtensa with both Bluetooth Classic and BLE.
Expect to pay about $42.00 - above the ~$20 typical for ESP32 boards.
Onboard you'll find a Grove connector, an IMU, battery charging via JST-PH and status LEDs (User).
- 3-channel DC motor driver (Texas Instruments DRV8836); drives up to 3 DC motors or 1 stepper motor
- JTAG debug connector for hardware debugging
- 1S LiPo support: onboard charging with reverse-battery, over-charge and over-discharge protection
- Two Grove connectors (one UART, one I2C)
- Built on the ESP32-WROOM-32 module
Where to buy
prices are typical street pricesRoboHeart Hercules
$42.00per unit, typical
Resources
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