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xobs | There's still some build weirdness with valentyusb. It has about a 50% chance of not working once synthesized. Tweaking the design fixes it. Hmm... | 00:25 |
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xobs | The interesting thing is that these builds *kinda* work, they just lock up after a few packets. I should see if it's Wishbone locking up or something else. | 00:28 |
xobs | The good news is that the USB<->Wishbone bridge looks entirely doable, and yesterday I got "reading" working (i.e. I was able to transfer 4 bytes back to the host, but the "ADDRESS" field wasn't working right so unless I hardcoded the address they weren't the _correct_ 4 bytes.) | 00:47 |
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mithro | xobs: Normally if you see that behaviour I would say that you are missing a timing constraint | 01:41 |
xobs | mithro: what do you mean by timing constraint? You mean that I have a clock network that's getting identified as the wrong frequency? | 02:10 |
mithro | xobs: A clock network which is missing a timing constraint (in ISE it was common to be cause by the constraint not making it through a PLL or other similar primitive) | 02:11 |
mithro | xobs: I would expose the current state of the import FSM as registers and check their values | 02:13 |
xobs | What's the import FSM? | 02:19 |
xobs | I was under the impression that it was the FSM, yeah. I thought maybe it was getting into an "ERROR" state, but I patched it so that it immediately exits that state, but that didn't change things. | 02:19 |
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xobs | mithro: according to the nextpnr output, the timing is all correct. | 03:26 |
mithro | s/import/important/ | 03:26 |
xobs | Though some of the async stuff has awfully short timings. | 03:26 |
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mithro | xobs: My goal for latchup is to help you get the valentyusb hardware rock solid | 03:43 |
mithro | xobs: I was also pondering seeing if we refactor valentyusb to look like the second diagram -> https://docs.google.com/drawings/d/1olpdWXglPGzJdW_R1DwWviBumlCetyuSZjl-luO_Xe8/edit | 03:44 |
tpb | Title: valentyusb - Parts - Google Drawings (at docs.google.com) | 03:44 |
mithro | Anyway home time for me | 03:46 |
xobs | mithro: that's my goal, too, since I'm planning on a trip to start production right after I get back. | 03:46 |
mithro | xobs: btw you have a form2 3d printer thingy right? | 03:50 |
xobs | mithro: yes, that's what I'm using to prototype the cases. | 03:53 |
mithro | xobs: could you print up some of the little programmers that were recently posted to the Tomu list? | 04:19 |
mithro | That way I can give out a sheet to Fomu hacker boards with a programming jig | 04:20 |
mithro | It was designed to be printed with a form 2 | 04:20 |
mithro | Much more portable then the factory jig :-) | 04:22 |
xobs | mithro: do you have any idea why "If((byte_counter == 1) or (byte_counter == 2) or (byte_counter == 3) or (byte_counter == 4)" gets turned into "if ((usb_byte_counter == 3'd4)) begin" in Verilog? | 04:26 |
xobs | Looks like it's a bug in migen: https://github.com/m-labs/migen/issues/137 | 04:36 |
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xobs | mithro: also, the FSM only gets into the "ERROR" state sometimes. Not always. I think there are two failures here. One where the transfer.py FSM goes into "ERROR", and another that I still haven't figured out. | 05:01 |
* xobs uploaded an image: image.png (598KB) < https://matrix.org/_matrix/media/v1/download/matrix.org/LfHVINpgPXElltvNGzwlhbsj > | 05:03 | |
xobs | The first one/two/three packets work successfully, but then things start to fail afte rthat. | 05:04 |
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tnt | xobs: (1) the fact the core doesn't use the IOB registers is often a recipe for random build results. (2) the 'async fifo' fix I really meant as a quick hack to see if that was the issue, but depending on clock drift between host/fomu I'm pretty sure it can still go wrong some times. Ideally the architecture of the RX pipeline should be fixed. | 06:38 |
xobs | tnt: I'm actually starting to suspect it has to do with the phase difference between the 48 MHz and 12 MHz domains. If I build using "--with-pll", the problem doesn't seem to happen. | 06:39 |
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xobs | I'm reasonably certain the issue is caused by skew, since it goes away when I use the pll. Nextpnr doesn't support cross-domain timing constraints, so that makes sense. | 09:28 |
xobs | Anyway. I have Wishbone reading working reasonably reliably now! Wishbone writing isn't quite there yet, but I just need to get the sequence right. And litex_server support is delightfully easy. | 09:29 |
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futarisIRCcloud | xobs: So the bridge is semi working now? We can read from the fomu using the bridge? | 23:15 |
futarisIRCcloud | https://github.com/potentialventures/cocotb - If anyone here hasn't already seen it. I wonder if we should start writing some testbenches for foboot and the like... | 23:17 |
tpb | Title: GitHub - potentialventures/cocotb: Coroutine Co-simulation Test Bench (at github.com) | 23:17 |
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