The bitaxehex from skot

optimize voltage regulator input and output capacitors

From a Discord chat today, there are some things on the TPS546 input and output cap filter sections that could be improved.

Switch electrolytic caps to ceramic. This isn't super straight forward because there aren't direct ceramic replacements for the 180uF el caps.

Try checking the OUTPUT_CAP_TYPE = ceramic option in Webench and see what they reccommend
check out this PDF from K1, especially the bit about Antiresonance
emi-murata.pdf
LCSC has some 100uF 16V ceramic capacitors that could work?

SMD Buttons are too small

not very practical to press. Maybe something bigger like TL3330AF260QG

Change power input to XT30

Replace the screw terminals with a PCB mount XT30

Document efficiency compared to other ASICs

I don't think this is fully accurate but I wonder if something like this could be added to the README to help users understand how this ranks compared to other ASICs:

The bitaxeHex actually seems super efficiency from a watts/terrahash perspective if it truly can hit 3.0TH/s on 50w power consumption at the wall.

I'm not sure if the $250 estiamte to build one is accurate with power supply.

My next question would be, if it really is $250 for 3.0 TH/s, what could be done to make it more efficent from a "cost input -> hash output" perspective? What would it take to support more then 6 BM1366 on a single board? Are there currently plans to support more?

change nominal TPS40305 output to 3.6V

the BM1366 wants 1.2V core voltage. for 3 in series this should be 3.6V.

the easy way to do this is change R10 from 1.54k -> 2k in the TPS40305 feedback circuit

C8 needs higher voltage rating

it's currently rated for 16V, which is very close to the nominal 12V and no good for 20V..

ESP-Miner dev status

Hi Skot. Way too remarkable to fit into accurate wordings about what I think of your project, and so I'll skip that part!

I'm going to press-on and go all-in this one. Getting ready to order the components so to rig a development board to follow along. Are we good to go on the tag:hex_v302 contribs or you advise us to wait until you've ironed it out more?

Power delivery stable on the v302? All good to go?

Use fixed LDOs and get rid of some resistors.

Suggestion:
Replace LDOs AP7331 with SGM2036s, and rid the resistors everywhere around them.
0V8 == SGM2036-0.8YN5G/TR
1V8 == SGM2036-1.8YN5G/TR

Need diode on 5V regulator output

When USB is plugged in without the main power supply attached, 5V gets fed back through the 5V regulator to VIN. This results in the 12V fans being powered by the USB 5V. The 5V regulator should have a diode after the output caps to prevent this.

Add BAP to Hex

Add the Bitaxe Accessory Port to the Hex so it's cross compatible with the Bitaxe

Level shifter Opamp Vs is outside recommended operating range

The TLV3544 used as the cross-domain level shifter is powered by VDD and -VDD which is most cases is 2.4V. The TLV3544 says the min Vs is 2.5V. (Although max operating doesn't have a min).

pmaxuw recommends setting Vs to 5V. This should be checked against the datasheet and/or tested.

Dedicated DC converter for each BM1366?

Sorry, that I use the issue tracker for this kind of generic question, but I don't know where else to put this.
I am about to build a bitaxeHex and was looking into more detail in the design and also other designs like the 0xaxe.
Everybody seems to go with a monolithic approach for providing power to all the ASICS from one source. But this doesn't seem to scale well to me. Wouldn't an approach to use a dedicated power of load regulator be more flexible and easier? Something like a 6A converter with programmable output (e.g. https://www.mouser.de/datasheet/2/1458/DS6203E_00-3104633.pdf). Costwise I don't think it makes a significant difference and it would open up the possibility to individually tune each BM1366 (not sure if that's possible at all though)?

Change the silkscreen for L1 and L2 by considering the "start of winding"

Pro tips from the doc said L1 and L2 should consider the EMI issue. i.e. the "start of winding" end should attach closer to the switch node.

R45 should be 10k

thanks to DevJune on OSMU

USB-C port needs clearance for plug enclosure

USB-C plug enclosures can be pretty chunky sometimes. I think we need some more clearance between the USB-C receptacle and the ESP32. Especially if anyones uses the built-in antenna variant.

Needs fiducials

Need to add fiducials for manufacturing.

C15 is wrong part size

C15 part is 0402 and should be 0805.

it should also be a little higher voltage. BP is 6V and the part is rated for 10V

3d model

is it possible to add the 3d model of the PCB assembled with all these components in order to draw (step) the box with the cooling circuit?

5V power from the USB-C connector

@skot Did we decide to remove the diode and 5V from the USB-C connector?

fan should be 12V

5V isn't ideal for bigger fans

Reset signals connected in parallel instead of series

As suggested on the Discord channel, perhaps we should connect the ASIC reset signal to each ASIC individually within the voltage domain instead of passing it through the ASIC chain. This should avoid any delays on the reset and have all the ASICs come out of reset at the same time.

Extender Voltage Range

As this would be a perfect Rig for PV powered mining wouldn't it be a good idea to have a greater Voltage In Range so that it could be powered from a 24 Volt Solar System? In this system you would have lower amps and it would have a better overall performance.

C20-22 are the wrong footprint

footprint is 1206, part is 0805

rackable version !

Hi

i just discover your project and imagin already a rackable version ..
i mean a daughter board with 8 ASICS and PSU and a connector to chain several boards ..
we can design a "mother board" with a single ESP32, a TFT screen and something to share / buffer links with each daughter boards..
maybe an FPGA, with 8 UARTs inside and some fifo ..
or use 8 software UART in the ESP32 ..?

a watercooling system maybe a better option too.. avoid some noise !

what is the actual status of your design ?

regards
phil

Add Efuse

For power monitoring and safety

update BM1366 footprint with latest from bitaxe v206 library

Change temperature sensors to a larger package

Some people have trouble soldering the tiny footprint of the temperature sensor. Change the temperature sensor to this part:
https://www.digikey.com/en/products/detail/texas-instruments/TMP1075DGKR/9692553
It's the same part, but a larger footprint. The software drivers can stay the same, no changes, and the larger footprint will be easier to solder.

Provide 3.3V to TPS546 for configuration

The TPS546 regulator will run on 3.3V without trying to start regulation. This mode is used for configuring the registers in the chip. If we route 3.3V over to AVIN on the TPS546, then we can use USB only to power up boards to flash the ESP32, and then reboot to allow the ESP32 to configure the TPS546 registers before applying main 12V power. Probably need a diode to prevent backfeed from the 12V rail.

Fan PWM may need a 5V pullup

Some fans require a 5V pullup on the PWM signal. Probably change layout to allow a 3.3V and/or 5V pullup... or maybe just a 5V pullup. Need to look into it.

core voltage is too high for ESP32 ADC measurement

The ESP32 measures the ASIC core voltage (TPS40305 output) via an ADC pin. 4.5V is too high to measure directly. put a voltage divider in there.

Add voltage sensing to each domain in order to check voltage balance

Add a voltage divider on each domain core voltage, and feed it back into the ESP32 so the firmware can measure the domain voltage balance and report it to the GUI.

Heatsink hole spacing

can we spread the mounting holes of the PCB Heatsink from 60.5 mm to 59,5 mm. there is a high risk of breaking the drill bit when drilling.

More heatsink mounting holes

More mounting holes are needed to prevent pcb bending and increase mounting pressure

Replace DigiKey Tape & Reel part numbers with Cut Tape ones in BOM

The current BOM references DigiKey part numbers for Tape & Reel (TR) packages with minimum order quantities of 10,000+. They can be easily substituted with the Cut Tape (CT) ones.

Ref	Current	Substitute
R2, R4	RMCF0402FT17K8TR-ND	RMCF0402FT17K8CT-ND
R5	RMCF0402FT10K0TR-ND	RMCF0402FT10K0CT-ND
R6	YAG3115TR-ND	YAG3115CT-ND
R10	311-26.1KLRTR-ND	311-26.1KLRCT-ND

Add pullup resistors to the I2C signals

It appears that the I2C signals from the ESP32 might already have pullups, but they are extremely weak. We should add our own pullups because the I2C signal goes across the entire board from end to end. Also, the PMBus spec calls out stronger pullups.

bitaxeHex-303-schematic.pdf missing

Hey guys, received all the passives and other components for assembly (less the BM1366 ofc). I've noticed the 303 gerbers are avail, which is great as I can get a dev board fab'd to follow-up with this project, however its ref schematic is missing. Any chance to have that uploaded or emailed?