ESP32-H4

Why it is more than an H2 refresh

The H2 and H21 are sensor-node chips: one slow core, 19 pins, minimal peripherals. The H4 keeps the H-series radio philosophy — 802.15.4 plus Bluetooth LE, no Wi-Fi — but scales everything else up enough to build a device rather than a sensor.

Two RISC-V cores instead of one, at 96 MHz, with a dedicated low-power domain for selected peripherals. Two cores in a mesh device is more useful than it sounds: the 802.15.4 stack and the Bluetooth stack are both timing-sensitive, and separating protocol work from application work removes a class of jitter problem.

35 GPIOs, nearly double the H2’s 19, plus 14 capacitive touch channels — enough for a remote control with buttons, or a panel.

Bluetooth 5.4 (LE), fully implementing the 5.4 core specification and certified against Bluetooth 6.0. This is a significant jump: every other H-series part is on BLE 5.0/5.3. 5.4 brings Periodic Advertising with Responses and Encrypted Advertising Data, and the version level is what unlocks LE Audio with the LC3 codec.

USB OTG and CAN FD, neither of which the H2 or H21 has. Espressif’s published peripheral tables list USB OTG for the H4; some secondary summaries disagree, so confirm against the final datasheet before committing a design that depends on it.

384 KB of SRAM with up to 4 MB of PSRAM support, versus the H2’s 320 KB and no PSRAM. Combined with I2S and a DC-DC converter, this is what makes audio applications feasible.

The applications this unlocks

Espressif positions the H4 for a distinctly different set of products than the H2:

• LE Audio devices — earbuds, hearing devices, broadcast audio receivers. LC3 with multi-stream needs the 5.4 stack, the buffer memory and the I2S path.
• Remote controls with displays — 35 GPIOs, touch, low power, and a Thread or BLE link back to a hub.
• Smart-home hubs — two cores let one chip run a Zigbee coordinator and BLE simultaneously.
• Indoor positioning — Bluetooth direction-finding and 802.15.4 ranging.
• Low-power BLE peripherals generally, where the H2 would be too pin-constrained.

What it still cannot do

No Wi-Fi. This remains the defining constraint of the H-series. An H4 cannot reach an IP network without a border router, a gateway, or a companion chip. If your product needs to talk to a cloud service directly over the home network, it needs a Wi-Fi part — either instead of, or alongside, the H4.

96 MHz. Two cores at 96 MHz is not a lot of compute. There are no SIMD extensions and no AI acceleration. Audio decode and mesh routing are within reach; image processing is not.

No display or camera interface. Screens attach over SPI, which caps you at small panels.

On security the H4 has hardware AES, SHA, RSA and ECC plus an ECDSA digital signature peripheral, but — like the H2 — no APM or TEE isolation.

Where it sits in the family

The H4’s closest competitor is not another H-series part but the S31 , which also has Bluetooth 5.4 with LE Audio and 802.15.4 — plus Wi-Fi 6, plus gigabit Ethernet, plus 320 MHz dual cores, plus real display and camera interfaces. The S31 is a much bigger chip in every sense, including price and power.

The H4 wins where power discipline matters. It is a 96 MHz part with a single-digit-microamp sleep current designed to run from a battery; the S31 is a mains-powered hub chip. If your LE Audio device needs to last a day on a small cell, the H4 is the right family. If it is plugged into a wall, the S31 gives you far more.

Choose it when

• You are building an LE Audio product on a battery
• You need Bluetooth 5.4 features specifically, at low power
• You need more pins and touch than the H2 offers, without Wi-Fi’s power cost
• You need CAN FD in a low-power, non-Wi-Fi device
• You are building a hub that must run Zigbee and BLE concurrently

Choose something else when

• You need volume production today → ESP32-H2
• You need Wi-Fi → ESP32-C6 or ESP32-S31
• You need the lowest possible sleep current on a simple sensor → ESP32-H21
• You need real compute, a display or a camera → ESP32-S3 or ESP32-P4