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Skot Croshere 8e8cad1e39 switched out some OOS parts, generated BOM
2022-10-04 16:17:22 -04:00

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The bitaxe

an early-stage experimental bitcoin mining machine. Uses a single Bitmain BM1397 ASIC (chip).

BM1397

BM1397 pic

  • The BM1397 is a undocumented SHA256 mining ASIC from Bitmain. It's mostly used in the Antminer S17
  • Bitmain claims the BM1397 has 0.045j/Gh efficiency
  • The BM1397 is available for around $20 each in low quantities from Aliexpress
  • The BM1397 has the same footprint as the BM1387, but a very different pinout.

Current Status

  • I have not built up any or tested any of these PCBs yet. Hopefully soon!

Hardware

  • BM1397 from random AliExpress seller. I got the "AG" variant. Not really sure what the difference is.
  • 40x40mm heatsink and 5V fan from a random AliExpress seller. At least half of these arrived broken in some way. But they are cheap and the working ones do keep the BM1387's nice and cool when used with some thermal compound.
  • The serial port is 1.8V. The FTDI TTL-232RG-VREG1V8-WE USB adapter does the trick, although it's pretty expensive.
  • jim.sh Micro1v8 FT230X adapters also work.
  • Neither the FTDI cable or the jim.sh adapter breakout any of the CBUS pins that could be used for the reset line.
    • for that I'm going to try the UMFT231XE-01 breakout board.
  • I added level shifters for the interface with the ESP32-C3 (Because it has 3.3V GPIOs)
  • I added a NCT218 so that the BM1397 core temperature can be read out over I2C
  • KiCad 6 design files
  • All of the parts on the board are listed in the KiCad BOM

Software

  • still TBD

Connections

Pin Name Description
VIN ASIC VIN - ASIC core voltage. Rumor has it this should be around 1.5V for the the BM1397. This needs more experimentation.
+5V 5V input gets regulated to 1.8V and 0.8V for the BM1397. Also 5V for Fan output. Not much current required. If the ESP32 is powered by USB, you don't need to power this.
+5V (Fan) 5V output for fan .
SPD (Fan) Speed input from fan.
VIO ESP32-C3 GPIO voltage (3.3V)
RXI 1.8V Serial input
TXO 1.8V Serial output
RST Inverted reset pin to the first BM1397. Unsure how necessary this is.
GND Common ground

Goals

  • Develop some firmware for the ESP32 to connect to a stratum server/pool over WiFi and get work for the mining ASIC
    • Firmware should monitor fan speed
    • Firmware should monitor BM1397 core temperature (via NCT218)
  • Develop some software in Rust to getblocktemplate from a bitcoin node and communicate work to a fleet of bitaxes.
  • add an onboard power sensor so we can set the hashrate (ASIC requency) and therefore current to extract maximum power from a solar panel.