Inside the Bitaxe: How an Open-Source ASIC Miner Goes from Schematic to Solo Block

Source: Dev.to

Introduction

If you have spent any time in Bitcoin circles over the past year, you have probably seen the photos: a tiny circuit board, roughly the size of a credit card, with a single ASIC chip, a small fan, and an OLED screen showing a live hashrate. It sits on someone’s desk next to a monitor, pulling 18 W from a USB‑C power supply.

That device is a Bitaxe, and it is one of the most interesting open‑source hardware projects to emerge in the Bitcoin ecosystem.

What makes Bitaxe worth paying attention to is not the mining output. At 1.2 TH/s, a single Bitaxe Gamma 602 represents a vanishingly small fraction of Bitcoin’s 800+ EH/s network hashrate. What makes it interesting is the engineering: a fully open‑source Bitcoin ASIC miner built around a reverse‑engineered Bitmain chip, an ESP32‑S3 microcontroller, and a firmware stack that anyone can audit, modify, and flash.

For developers and hardware tinkerers, there is a lot to unpack here.

The Architecture

Every Bitaxe model shares the same core architecture:

Current models

All schematics, PCB layouts, Gerber files, and bill of materials are published at bitaxe.org and on Skot’s GitHub repository. The firmware, ESP‑Miner, is also fully open source—every copper trace on the board is documented.

The Firmware: AxeOS

AxeOS is where the Bitaxe becomes genuinely useful as a developer platform. The firmware runs on the ESP32‑S3 and exposes a full web interface accessible from any browser on the local network. From AxeOS you can configure:

• Stratum pool URL and port
• Bitcoin wallet address (stratum user)
• ASIC frequency and core voltage (overclocking)
• Fan speed and thermal thresholds
• Autotune mode – automatic frequency/voltage optimization
• OTA firmware updates

Autotune

The autotune feature incrementally adjusts ASIC frequency and voltage, monitors temperature and hashrate stability, and settles on an optimal operating point for your specific chip. Because of the silicon lottery (natural variance in chip manufacturing), two identical Bitaxe units will often stabilize at slightly different frequencies. Autotune handles this automatically.

The entire AxeOS codebase lives at github.com/skot/ESP‑Miner. It is written in C using the ESP‑IDF framework, and pull requests are active. If you want to contribute, the ASIC driver layer and the Stratum V1 implementation are the two most impactful areas.

What Actually Happens When It Mines

1. Boot – AxeOS connects to your configured Wi‑Fi network.
2. Pool connection – Opens a TCP connection to the Stratum pool and requests work.
3. Work receipt – The pool sends a block template (transaction data, previous block hash, target difficulty).
4. ASIC processing – The ESP32‑S3 passes this work to the BM1370 via a serial interface. The ASIC iterates through nonce values at ~1.2 trillion attempts per second (Gamma 602), computing a double SHA‑256 hash for each.
5. Share submission – If the resulting hash is below the target difficulty, the Bitaxe submits it back to the pool as a valid share.

• Pool mining – Any share meeting the pool’s difficulty earns proportional credit toward the next block reward.
• Solo mining – Only a share meeting the full network difficulty counts. As of February 2026, that difficulty exceeds 114 trillion.

The probability math is straightforward: a 1.2 TH/s device against a network of 800+ EH/s has roughly a 1‑in‑850,000 chance of solving a block on any given day. Each hash is an independent Bernoulli trial; there is no “building toward” a solution—every hash is equally likely to be the winning one.

When the Improbable Happens

Despite those odds, Bitaxe devices have found confirmed Bitcoin blocks:

These finds demonstrate that even low‑hashrate, open‑source miners can contribute to Bitcoin’s security and earn real value.

Closing Thoughts

Bitaxe showcases what is possible when a community‑driven, fully open‑source approach is applied to Bitcoin mining hardware. For developers, it offers:

• A transparent hardware stack (schematics, PCB files, BOM)
• An extensible firmware platform (AxeOS) with OTA updates and autotuning
• A real‑world testbed for experimenting with ASIC drivers, Stratum protocols, and low‑power mining strategies

Whether you’re looking to contribute code, design a custom board, or simply understand the inner workings of a Bitcoin ASIC miner, Bitaxe provides a solid, documented foundation to build upon.

Running on Umbrel

The reward was 3.141 BTC, roughly $347,000. The miner was running a fully sovereign stack: his own hardware, his own node, his own pool software. No third‑party was involved at any point in the process.

In total, open‑source mining hardware has found at least five confirmed blocks since July 2024, with combined rewards exceeding $1 million in BTC. The interval between finds has been compressing: 229 days, 179 days, 52 days, 25 days. More devices in the field mean more aggregate hashrate, which means more statistically expected wins.

The Protocol Layer: DATUM and Stratum V2

The Bitaxe currently communicates with mining pools using Stratum V1, the protocol that has been the industry standard since 2012. In the V1 model, the pool constructs the block template and sends it to the miner. The miner hashes it and has no say in which transactions are included.

Two newer protocols are changing this dynamic.

DATUM

Developed by Ocean.

• Miners build their own block templates using their own Bitcoin node’s mempool data.
• The miner selects which transactions to include, constructs the coinbase transaction, and submits the completed work to the pool.
• The pool handles coordination and payout, but the miner retains editorial control over block contents.

Stratum V2

• Pursues a similar goal with a different architecture.
• Introduces encrypted communication between miner and pool.
• Reduces bandwidth requirements.
• Supports a “job declaration” mode where the miner can propose its own block templates.

For Bitaxe owners running a home node (via Umbrel, Start9, or a bare‑metal setup), these protocols transform the device from a passive hash generator into an active participant in Bitcoin’s consensus process. You are not just submitting hashes—you are deciding what goes in the block.

Note: Neither protocol is fully integrated into AxeOS at the time of writing, but development is active. The OSMU (Open Source Miners United) community on Discord is the primary coordination point.

Building or Buying

Build it yourself

1. Order the PCB from JLCPCB or PCBWay using the published Gerbers.
2. Source the BM1370 from NBTC on AliExpress (≈ $15 per chip).
3. Order the remaining BOM from Digi‑Key.
4. Solder it yourself – the BM1370 is a BGA package that requires reflow soldering; the passives are 0402 and 0201 size. You’ll need a stencil, solder paste, and either a reflow oven or a hot‑air station with steady hands.

Buy a pre‑assembled unit

• Solo Satoshi assembles and tests every unit in the USA, ships same‑day, and includes a 90‑day warranty.
  • Bitaxe Gamma 602: ≈ $98
  • NerdQaxe++ Rev 6.1 (four BM1370 chips, 6+ TH/s): ≈ $382

The open‑source nature of the project means you are not locked into any vendor. If you buy a Bitaxe from any seller, you can flash it with the latest AxeOS firmware, point it at any pool, and configure it however you want. The hardware is yours. The firmware is yours. The keys are yours.

Bitaxe 600 PCB 3‑D Render

Why Developers Should Care

Bitaxe sits at the intersection of embedded systems, cryptographic protocols, network engineering, and economic incentive design. It is a real‑world system that combines:

• Low‑level ASIC driver development (C, ESP‑IDF)
• Networking protocol implementation (Stratum V1/V2, TCP sockets)
• Cryptographic hashing (SHA‑256 double hash, nonce iteration)
• Hardware design (4‑layer PCB, BGA soldering, thermal management)
• Distributed systems (pool coordination, block propagation, difficulty adjustment)

If you are looking for an open‑source project where your contribution has tangible, measurable impact on a live production network processing billions of dollars in value daily, this is one of the few that qualifies.

• The ESP‑Miner repo accepts pull requests.
• The OSMU Discord has active hardware and firmware channels.
• The BM1370 register map is partially documented but still has gaps—one of the highest‑impact reverse‑engineering opportunities available in the Bitcoin hardware space right now.

Eighteen watts. One chip. A live connection to the most valuable computational network on earth.
The code is open. The schematics are public. The blocks keep getting found.

Matt Howard is the Founder and CEO of Solo Satoshi, a Bitcoin home‑mining hardware retailer based in Houston, Texas, that has shipped over 40 000 open‑source mining devices to 70+ countries.