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Topic: Bus Pirate "Ultra" v1a & v1b with ICE40 and Icestorm :) (Read 4249 times) previous topic - next topic

Re: Bus Pirate "Ultra" v1a & v1b with ICE40 and Icestorm :)

Reply #60
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Received 100 Bus Pirate cables using our pinout colors from DirtyPCBs.com custom cable service. The cables were just over $1 each for quantity 100.
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The primary reason we ordered these now is to get a feel for how the pinout color scheme works in practice before we commit to it permanently.
The leads are 30cm long, which seems a bit unwieldy in real life. The next version will be a few centimeters shorter.

The ends are terminated with 1 pin female "Dupont" connectors. These are easy to use with breakout boards and bread boards that have 2.54mm header pins. We'll need to choose a nice probe hook and mating crimp eventually.

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While the wire quality is fine, it's a bit stiff and unpleasant to work with. We're still looking for the perfect wire. The Saleae Logic cable has really amazing tangle free wire with great flexibility. We took the Saleae cable to a bunch of wire manufacturers in Shenzhen, but none of them had anything close in terms of quality and flexibility. They did confirm that it is not silicon coated wire, so our search will continue.
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Re: Bus Pirate "Ultra" v1a & v1b with ICE40 and Icestorm :)

Reply #61
I have bought these jumper cables [1] from AliExpress and they are super nice and flexible. They are advertised as being made from silicone wire.

[1]: https://aliexpress.com/item/32811041093.html

Re: Bus Pirate "Ultra" v1a & v1b with ICE40 and Icestorm :)

Reply #62
Very nice. If you bend the wire really hard does it leave a crimp in the wire? I bought various samples of silicone insulated wire from the market in Shenzhen, and while it is a big improvement over PVC wire, they are all kind of "floppy" and easily left with a permanent crimp when bent 180 degrees.

Someone also suggested we look at multimeter probe wire and suppliers, which has been pretty promising as well. According to a few probe datasheets I've read, the wire is double insulated with silicone in two different colors so bends and abrasions are readily apparent.

Overall it feels like we are getting closer :)
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Re: Bus Pirate "Ultra" v1a & v1b with ICE40 and Icestorm :)

Reply #63
Whether it leaves a kink in the wire depends on the radius of the bend. A radius greater than ~3 mm don't seem to do anything to the cable.

Besides the material of the insulation you also have to look out for wires with very fine strands. These tend to be much nicer and more flexible.

Re: Bus Pirate "Ultra" v1a & v1b with ICE40 and Icestorm :)

Reply #64
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We received the v1d PCB, stuffed it, and tested the new power supply features :) Going great so far!

Next we'll get the ADC (went 12 bit) going from the FPGA, and then add the display board with the bigger 2.8" LCD.
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Re: Bus Pirate "Ultra" v1a & v1b with ICE40 and Icestorm :)

Reply #65
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I've located a couple suppliers with silicone coated fine strand tinned wire that look promising. I'm getting samples in 20AWG (1.80mm OD) to have a look at the colors and quality.
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Re: Bus Pirate "Ultra" v1a & v1b with ICE40 and Icestorm :)

Reply #66
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Reading the ADS4072 ADC using commands sent to the FPGA. This is great! Even with the really long delay I inserted for testing, the measurement is precisely timed. I don't see any of the extreme latency and delay that was cropping up when we paused the FPGA state machine to let the MCU take the analog measurement. Can't wait to get the DAC connected to the FPGA too.

Here's some build notes:
*R900 wrong size ()
*R15 wrong size (1210)
*many 0603 0.1uf/1uf->0402
*2 R on back current shut ddown are 0603->0402
*U101 to 208mil (128mbit flash)
*R908/910 -> 100K
*changed 909,911,912 to 1K
*C306 shoud be 0402
*According to Twitter, vcc and ground should be separated on the flex connector to avoid shorts when it moves

*add mcu ADC connection to cs, other minor changes to cs outlined in the updated schematic
*We need to replace (try) the 245/573 with 4 x 74lvc2t45s
*LED anode and cathode are reversed on the 2.8" LCD connector
*200R protection resistors from FPGA to driver nt45 ICs.
*Pull down on the MUX and 245 enable/direction pins

Things to think about:
*3volt analog reference
*move remaining control to FPGA
*Maybe remove the open drain drivers if we end up with 4x 2T45s (and associated pull-X resistors on direction pins)
*2 x 4051 instead of 4067 (cost, supply issues)
*Choose proper diodes for the op amp protection
*VREG LED and VREG status detection
*What to do with USB LED?

Things to test on this version:
*back current protection using the new ADC connections
*probe all points of the PSU
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Re: Bus Pirate "Ultra" v1a & v1b with ICE40 and Icestorm :)

Reply #67
XX We identified four factories selling highly flexible silicone coated wire with fine tinned copper stands. The smallest (common) strand size for Chinese factories seems to be 0.08mm, with 60 strands in a 22AWG wire. The first set of samples arrived this week, three more should be here next week.

The only issue seems to be purple, not much out there in purple. Also, if we want the hip unprinted wire its going to take a fairly massive MOQ. If we end up customizing the wire, at least we have the chance to get the exact colors we want.

The screenshot is from a WeChat sight that Jam and Abin sent from the Shenzhen office :) It looks really flexible and kink-free.
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