Project Timeline:
August 4, 2013 - Low output capacitance reason for low overclockability, added 1000uF (from 2200uF) and achieved 350, added another 1000uF and can probably go to ~390 but software issues need to be correctedAugust 2, 2013 - Trying to hunt down a bug that is causing the miner to stop working after some random time; As temp fix, wrote python script for RPi to reset miner via GPIO when not responding
July 31, 2013 - PCB fully populated with 10 chips; Hashing at 300 MHz (having issues above 300); Second PCB populated with remaining 4 chips; Board chaining appears to work
July 30, 2013 - PCB mistake found relating to SPI (corrected); Microcontroller correctly decoding nonces;
Finally getting valid nonces!; Hashing with cgminer working (but with external FT232 chip)
July 29, 2013 - 10 chips received from zefir
July 28, 2013 - PCB populated (1 chip); PCB mistake found relating to microcontroller (corrected)
July 22, 2013 - PCBs received
July 12, 2013 - Simple prototype PCB etched and testing underway
July 11, 2013 - Heatsinks received; 4 sample chips received from zefir (Thanks!)
July 8, 2013 - Prototype PCBs shipped from manufacturer
July 3, 2013 - Components received
July 1, 2013 - Components ordered (minus heatsink)
June 30, 2013 - Board design sent out to be manufactured
June 29, 2013 - Requested 4 sample chips from zefir
June 28, 2013 - Double-sided board design mostly complete; Added microcontroller to board
June 19, 2013 - Microcontroller identified by cgminer using icarus protocol; Single layer board abandoned
June 9, 2013 - Project announced
Detailed Update Info:
July 30, 2013 -
Board fully populated...
July 22, 2013 -
PCBs received...
July 12, 2013 -
Temporary prototype testing board etched. Testing platform shown below...
June 28, 2013 -
The board design is pretty much finished. As I mentioned in the thread, I decided to abandon the single layer homemade board and I focused my effort on the double layer board. I originally was going to modify the single layer board to double layer, but I started from scratch on the double layer board to improve the layout. It was a challenge to route the traces while trying not to excessively cut up the ground and power planes. I also decided to put a microcontroller on the board, the LPC1343. It's not the cheapest option but I'm most familiar with the LPC microcontrollers. I also added a thermistor. There is also some prototype circuitry that will probably not be needed in the final design (if I decide to even make a final design). The board design will be sent off for manufacture in the next few days. Here are the front and back layers...
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Original Post -
Hello everyone. Last month I announced my intention of building my own Avalon based mining board, but I didn't make an official project thread, until now. I wasn't going to start this thread until I had the board finished, but I've been working on it pretty slowly since I won't be getting a sample chip and the main batch of chips won't be arriving for quite some time.
Originally, I was going to design a single board with both the MCU and Avalon chips on it, but I decided to first make just a board with the Avalon chips and the user can use whatever MCU they want with it. I will probably make a separate controller board eventually.
I'm calling my project the "Davalon" miner for now (Dan and Avalon mixed together). This is a DIY project, I currently don't intend to sell anything. Design will be open source.
I am designing two versions of the board. One is for etching the board at home. The board is essentially single layer with a lot of jumper wires. This is the board shown below. It has a lot of pads for soldering fine 30 gauge wire to it. The other version is a double sided board for a PCB fab to manufacture. It will not have all the pads for soldering wires and it will have proper thermal vias.
The area around the chips is pretty much finished, apart from the thermal vias. The right side of the board is still under construction. Mounting holes to be added.
Here are some board specifications:
- 10 Avalon chips
- 150mm x 50mm
- Double-sided board
- D12S05020 DC-DC Converter Module (20A)
- Stackable vertically and horizontally
- Boards can be chained together and controlled through one controller board
- 4-pin molex power or 3 wire terminal block
The board can be stacked vertically (one on top of the other) using board spacers. Now imagine you have several boards stacked on top of each other. Put this stack on its side and that's what I mean by "stackable horizontally".
The config and report lines broken out to a 2x4 pin header, apart from the main connector for the controller. This 2x4 pin header is used to chain the boards together while still using one controller. The top 4 pins are for the input and the bottom 4 are output. Using a 4-pin 0.1" female-to-female jumper cable, the output of one board is connected to the input of another to chain them. The config and report lines are also buffered similarly to the official Avalon miner.
Currently the design requires 12v and 5v, supplied by the 4-pin molex power connector. A 3-wire terminal block is added so that power can be distributed using wires in case there is not enough 4-pin molex power plugs on you power supply. The design may be changed to use only 12v.
So far the only solution I have for the heatsink is a 100mmx50mm aluminum heatsink secured to the board using adhesive thermal pads.
I was going to add variable voltage control using a programmable resistor, but there were some design issues that I didn't want to deal with. The main issues were getting the voltage back to the controller from each board to be measured and chaining I2C between all the boards to communicate with the programmable resistor. If I had a MCU on each Avalon chip board, then these issues would not be a problem.
That's all for now. Thanks for your interest.
