ESP32-H2

Why remove Wi-Fi

Wi-Fi is expensive in every sense: die area, peak current, average current, and the RAM the stack consumes. A Wi-Fi transmission can draw a few hundred milliamps in bursts, and even an idle associated station must wake periodically to listen for beacons.

For a door sensor, a temperature probe or a light switch, none of that is wanted. What is wanted is a radio that can send twenty bytes, occasionally, using as little energy as possible, on a network that routes around dead nodes. That radio is IEEE 802.15.4 — the physical layer beneath both Thread and Zigbee — and the H2 is Espressif’s part built entirely around it.

The H2 also carries Bluetooth LE 5 with Long Range (coded PHY), advertising extensions and mesh support, which covers commissioning from a phone and BLE beacon use cases.

The consequences of no Wi-Fi

An H2 cannot reach the internet on its own. There is no IP-over-Wi-Fi path and no Ethernet MAC. Every H2 deployment requires something else on the network to act as a border router (for Thread) or a coordinator/gateway (for Zigbee) — commonly an ESP32-C6, a commercial hub, or a Home Assistant installation with a compatible radio.

That is not a flaw; it is the architecture. Mesh end devices are supposed to be dumb, cheap and long-lived, with the intelligence and the mains power at the border. But it does mean the H2 is never a one-chip solution.

Architecture and power

A single RISC-V core at up to 96 MHz — the slowest in the current family, deliberately. 320 KB of SRAM plus 4 KB of LP SRAM that survives deep sleep.

Deep-sleep current is 7 µA. There is no LP core, only LP peripherals — timers and sensors that can run and wake the main core, but no coprocessor executing your code during sleep. For the duty cycles these devices use (wake, read, transmit, sleep for ten minutes) that is usually sufficient.

Security is better than the price implies: hardware AES-128/256 with DPA protection, SHA, RSA, ECC and HMAC, an ECDSA digital signature peripheral with eFuse-held keys, and — notably — ECC-based secure boot, which is more modern than the RSA-based secure boot on the older parts and produces smaller signatures.

Peripherals

• 19 GPIOs — enough for a sensor node, not for much else
• 2 SPI (one dedicated to flash), 2 UART, 2 I2C, 1 I2S
• USB Serial/JTAG for flashing and debugging
• 4 RMT channels (2 TX, 2 RX) — so unlike the C2 and C61, IR and addressable LEDs work
• TWAI (CAN), MCPWM, PCNT, GDMA
• 5-channel 12-bit ADC, temperature sensor
• No SD/MMC, no touch sensing, no camera or LCD interface

Modules and boards

ESP32-H2-MINI-1 from $2.03, with -H4S (4 MB flash) at $2.07 and U external-antenna variants at $2.13–$2.19. Bare chips: ESP32-H2 $1.39, ESP32-H2FH4S $1.46.

ESP32-H2-DevKitM-1-N4S is $10. Espressif’s longevity commitment runs from 2021.

H2 versus H21 versus H4

The H-series now has three members, and they are close together:

The H2 is the one you can actually buy in volume today. The H21 is a refinement of it (better efficiency, more range) and the H4 is a step up (two cores, newer Bluetooth, far more pins) — but both are still ramping. For a product shipping now, the H2 is the H-series.

Choose it when

• The device is battery powered and must last years
• It joins a Thread or Zigbee mesh with a border router already present
• You are building a Matter-over-Thread end device
• You need BLE mesh lighting or long-range BLE
• Wi-Fi is genuinely unnecessary — the H2 is cheaper and lower power precisely because of it

Choose something else when

• The device must reach the internet unaided → ESP32-C6
• You need more than 19 GPIOs → ESP32-H4 when available, or ESP32-C6
• You need the absolute lowest sleep current → ESP32-H21 at 5 µA
• You need Bluetooth 5.4 or LE Audio → ESP32-H4 or ESP32-S31
• You want one chip that does both Wi-Fi and Thread → ESP32-C6