Thursday, 2019-03-21

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mithroxobs: Did you see ?00:38
tpbTitle: Linux on VexRiscv · Issue #60 · SpinalHDL/VexRiscv · GitHub (at
futarisIRCcloudmithro: Looks like kgugala has it running on Arty.01:02
xobsmithro: I did, but I thought it was too heavy for ice40.01:04
xobsI've been concentrating more on things like the smaller, non compliant MMU, and getting hardware dsp support.01:05
xobsIt's good to know it's progressing nicely!01:05
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futarisIRCcloudmithro / xobs: I saw whitequark recently added a rgb_input module to glasgow. RGB555 parallel bus.
tpbTitle: Glasgow/ at master · GlasgowEmbedded/Glasgow · GitHub (at
xobsfutarisIRCcloud: that's using their PMOD bus, isn't it?01:33
futarisIRCcloudxobs:  / #glasgow01:37
futarisIRCcloudI think it has a 16 pin bus...01:37
futarisIRCcloud15 for pixel data, 1 for pixel clock.01:38
futarisIRCcloudSampling all 16 @ 22.5Msps, so you should be able to run 640x480x60Hz over that. 848x480x60Hz would be near the limits.01:42
futarisIRCcloudWhoops I meant 848x480x50Hz.01:42
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xobsThat's bizarre. If I touch the blue lead of the RGB LED with a high-impedence scope probe, it turns on. What might cause that?06:43
tntWith a good led, 3 uA would be visible in some condition.06:47
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xobsNo, I know why it's lighting up -- some of the soldermask got scraped away, and I'm mirroring the signal on TOUCH_2, so what I'm actually doing is connecting LED_B to TOUCH_2.  Which is interesting, because that means that the LED pins are probably floating.07:08
tntah, so bad solderjoint ?07:15
xobsI don't think so. If that were the case, it would actually be three bad solder joints (the R, G, and B pins), since the 3.3V pin is working just fine.07:16
tntbut you said you checked the RGB outputs of the fpga ?07:32
MadHackerxobs: LED output probably only pulls one way, so if it's off, it's floated rather than pulled high/low.07:55
xobsI thought I did, but I'd like to amend that statement by saying that I just checked, and it looks like it's not working.07:56
xobsThe only thing the RGB pins are doing is leaking HFOSC.  I have them hooked up to SB_IO, and they ought to be outputting values, but they're not.07:57
xobsIt's leaking HFOSC at like 20 mV, so it's not much, but I'm totally not seeing any output.07:57
tntxobs: well no .. they're open drain, so they can be floating or connected to GND.08:00
tntyou need to put an external pull up and then you can see how they behave.08:00
tntah well I guess the led should act as a pull-up so you should be reading 3v308:02
xobstnt I thought I read that it could be used as a general-purpose I/O, but you're right even in that mode it's open-drain only.08:03
xobsSo I know the LED on this one board is good.08:07
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xobsOh that's interesting on Yosys: "ERROR: cell type 'SB_IO_OD' is unsupported"08:23
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xobsOkay, I scraped away the soldermask so I could measure two of the three lines.  Green is stuck at 1.5V, and blue is stuck at 1.2V.  They should be going through a PWM.08:35
tntDo you have several boards btw or just one ?08:40
xobsI have 100 boards, though I've destroyed a few.  One poor board sacrificed itself for me to discover the crystal was installed upside-down.  (It needs to go the opposite of what the datasheet says)08:42
xobsAnd I just verified the exact same thing on a second board -- C5 is at 1.2V, and A5 is at 1.5V.  They're not pulsing.08:46
xobsAnd now I'm onto a third board.09:06
xobsrohitksingh_work/rohitksingh  (or anyone else with a working hacker board): could I have you test this bitstream to see if it works?  I'm wondering if it's my test code, or if it's maybe something else.09:10
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xobsWell, bugger.  My schematic has pin A3 labeled as "GND", when in fact it's "VCCIO_0".  Guess this batch is mostly getting scrapped.09:14
MadHackerOops. That'll break it. Could toast off the offending track before placing if you desperately needed to salvage the batch?09:16
MadHacker(assuming more than one vccio_0)09:17
xobsMadHacker: nope. via-in-pad09:17
MadHackerThat's easier, spot-face cutter.09:17
xobshow's that?09:17
MadHackerYou know the tool you use for veroboard?09:17
MadHackerLike a drill.09:17
MadHackerJust scrape off the top of the via.09:18
xobsI'm not sure how I'd do that.  These ICE40s are really hard to unsolder and solder back on.09:18
MadHackerNo use unless you have another way to get VCCIO into it though.09:18
MadHackerHow close is it to anything else? Could just run a drill straight through the via from the far side and core it out, if it's a through via.09:19
MadHackerJust don't go heavy-handed on the drill and go through the chip. :D09:19
MadHacker(Spot the person who has to deal with very very very short deadlines and rework is the only option...)09:19
xobsIt's... possible... USB_N is on the other side, and layer 3 actually has 3.3V and VCCPLL (which are basically the same thing), it's just layer 2 that has GND.09:20
tntHow does USB ever works ?!?09:20
xobstnt: I haven't gotten around to testing USB, but you're right that wouldn't work either.09:21
tntbtw vccpll is 1v2 not 3v309:23
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xobsWell, that is very sad.09:42
xobsOn the bright side, now I have 100 boards that I can use for testing NVCM programming.  And case design.09:42
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tntxobs: yeah :/09:52
tntDefinitely interested in finding your NVCM results :)10:04
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futarisIRCcloudxobs: I have 4 hacker boards.11:14
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