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Arduino Bitcoin Miner (plain C and AVR assembly versions)
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README.md

arduino-bitcoin-miner

Arduino Bitcoin Miner

Video

Arduino Bitcoin Miner

Software

Hardware

Usage

Build and upload sketch in Arduino IDE. Arduino will work as a serial port Bitcoin miner (namely Icarus, device id ICA 0). Run BFGMiner from the command line using testnet-in-a-box address and an Arduino COM port, e.g. for COM5 that would be:

bfgminer -o http://localhost:19001 -u admin1 -p 123 -S icarus:\\.\COM5

Or, for the mining pool (e.g. btc.com):

bfgminer -o stratum+tcp://us.ss.btc.com:25 -u test.001 -p 123 -S icarus:\\.\COM5

Hashrate

Current hash speed is pretty abysmal, considering the 16 MHz Arduino Pro Micro (ATmega32U4 at 5v):

  • ~ 50 hashes a second for arduino-bitcoin-miner.ino
  • ~ 150 hashes a second for the AVR assembly version

At this rate you would need about an year to find a single share. For the commercial Cryptovia library (42744 cycles per 50 bytes) it would be roughly the same number of hashes (16MHz / 42744 / 2 ~ 187Hz), maybe even less. All given values are for double hashing the 80-byte block header, so every hash takes two 64-byte SHA256 blocks, consdering midstate optimization.

What if

According to Mining Profitability Calculator, mining $1 a day needs 1.5 TH/s, 1 BTC a year needs 42 TH/s (numbers may vary).

  • At 150 hashes a second per Arduino, mining one dollar a day would need 10 billion Arduinos
  • Pro Micro consumes 200 mA, mining $1 a day with a 10 billion Arduino rig will need 2 gigawatts of power (Great Scott!)
  • With an average price $0.2 per kWh, 2 gigawatt mining rig will cost you about $10M a day (minus one dollar you make)
  • If you prefer a single AVR chip, mining 1 Bitcoin on ATmega32U4 will theoretically take about 280 billion years

Emulator

There is also a PC version of the serial port miner (see pc_version directory). You will need a serial port emulator, e.g. com0com. It creates COM port pairs, e.g. you listen on COM8 and specify COM9 for the BFGMiner. Emulator hash speed is currently about 1.14 million hashes a second (could be improved, maybe 6-7 million hashes per CPU core).

Testnet-in-a-box

To debug solo mining on the localhost you'd need testnet-in-a-box. Get the setup here: https://github.com/freewil/bitcoin-testnet-box. There are two debug modes - testnet and regtest, edit configuration files and set testnet=1 or regtest=1 accordingly.

Testnet mode mining works with old bitcoin-core releases only. I use bitcoin-qt 0.5.3.1 (coderrr mod with a coin control feature). Get it here: https://luke.dashjr.org/~luke-jr/programs/bitcoin/files/bitcoind/coderrr/coincontrol/0.5.3.1/

Regtest (regression test mode) is a preferred method for debugging new bitcoin-core versions (I've used 0.16.0). You need to download or generate at least 1 block to enable mining or you get RPC error 500 "Bitcoin is downloading blocks". Either use "generate 1" in bitcoin-qt (Help - Debug Window - Console) or use a Python script to run commands via RPC:

import requests
requests.post('http://admin1:123@localhost:19001', data='{"method": "generate", "params": [1]}')

Both testnet and regtest work well with cpuminer (and it supports fallback from getblocktemplate to getwork for old clients):

minerd -a sha256d -o http://localhost:19001 -O admin1:123 --coinbase-addr=<solo mining address>

CGMiner 3.7.2 also supports testnet and getwork, use --gpu-platform 1 for laptop nvidia cards (1030 gives about 200 Mh/s):

cgminer -o http://localhost:19001 -O admin1:123 --gpu-platform 1

Protocol

This miner uses Icarus protocol via USB serial port emulation (there is no USB autodetection, you have to specify a COM port).

Icarus

  • No detection is needed (no special command for this).
  • Wait for data. Each data packet is 64 bytes: 32 bytes midstate + 20 fill bytes (any value) + last 12 bytes of block header.
  • Send back the results, i.e. when valid share is found, send back the 4-byte result nonce immediately.

Read more about the protocol here: http://en.qi-hardware.com/wiki/Icarus#Communication_protocol_V3

BFGMiner specific

  • BFGMiner tests block with nonce 0x000187a2 first. Since we need to test only 100258 values the reply should be instant.
  • Sends work division payload 2e4c8f91(...). Expects 0x04c0fdb4, 0x82540e46, 0x417c0f36, 0x60c994d5 for 1, 2, 4, 8 cores.
  • If no data sent back in ~11.3 seconds (full cover time on 32bit range at 380MH/s FPGA), miner sends another work.

USB autodetection

Not implemented yet, you have to specify a COM port in the command line. Original Icarus uses either VID_067B & PID_2303 (USBDeviceShare) or VID_1FC9 & PID_0083 (LPC USB VCom Port driver). Default Arduino Leonardo driver uses VID_2341 & PID_8036, and neither BFGMiner nor CGMiner recognize it as an USB mining device. Changing hardware ID's requires updating bootloader and fixing the driver.

Algorithms

Sha256d

As the majority of Bitcoin miners, this one also uses midstate hashing optimization. Midstate is a 32-byte long data string, a part of the hashing function context after processing the first 64 bytes of the block header. Simply apply the state from the payload, process the remaining 16 (80-64) bytes of the block header (including nonce in the end), and hash the result.

// apply midstate
SHA256_Init(&ctx);
memcpy(&ctx.h, midstate, 32);
ctx.Nl = 512;

// set nonce and hash the remaining bytes
*(uint32_t*)(block_tail+12) = htonl(nonce);
SHA256_Update(&ctx, block_tail, 16);
SHA256_Final(hash, &ctx);

// hash the result
SHA256(hash, 32, hash);

Scrypt

Scrypt is not supported (yet). ATmega32U4 only has 2.5K RAM, so even basic Scrypt-based cryptocurrencies are not feasible, for example, Litecoin uses Scrypt with 128 KB RAM (in order to fit into a typical L2 cache). Other cryptocurrencies have even higher memory requirements, e.g. CryptoNight algorithm used in Monero requires at least a megabyte of internal memory.

References

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