Wednesday, 2019-04-10

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xobsI managed to get the picorv spi block working in litex, and I think that the reason it was't working is that I need to swap endianness for riscv.  I'll give that a shot tomorrow!  If that works, then you'll be able to use Foboot to load riscv code.14:45
xobsI also got a frist draft of a 3D case done, in case people want to 3D print one of their own.14:48
CarlFKxobs: are you coming to Latch-up in Portland next month?14:55
tpbTitle: Latchup (at
AmosSamxobs: didn't you said that you use vexriscv? So, foboot will be able to load either bitstream or riscv code? Wow14:56
xobsCarlFK: I wasn't planning on it. It does seem interesting, but I'm not sure I have the time/funding. Let me look.14:59
CarlFKthere will be a fpga hackfest on Friday14:59
CarlFKeither at the venue or a portland hackerspace14:59
xobsAmosSam: Yeah, it'll look for the sync pulse that indicates an ICE40 bitstream, and if it doesn't see it then it will just jump to the address.14:59
xobsMaybe a program header is in order...15:00
CarlFKhackerspace is open all night, venue is closer to hotels.15:00
AmosSamAnd will picorv core have access to usb?15:04
xobsAmosSam: I'm just using the picorv SPI hardware.  It's still the vexriscv code.15:05
xobsBasically, since I'm not doing a reset, anything the bootloader has access to the program can do.15:06
xobsSo you'll be able to write a USB driver, yeah.15:06
AmosSamSo, for program to communicate over usb, it will "only" need usb driver?15:07
xobsYep!  It's a way for people to get started with Fomu, programming RISC-V.15:07
AmosSamAnd still have access to fpga if they want/need it. I like it :-D15:09
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mithroxobs: Yes, the plan is to hack on litex / timvideos / fomu stuff at the hackfest before LatchUp15:54
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mithroxobs: Might be of interest to you ->
tpbTitle: eda-ricercatore (Zhiyang Ong) / Repositories ยท GitHub (at
mithrostd-cell-library-characterization - A repository for my experimental results, and scripts to process, analyze, and interpret them.17:09
mithro - Design of a 32-kbit synchronous SRAM with 32-bit words, using 180 nm process technology.17:10
tpbTitle: GitHub - eda-ricercatore/Modica-SRAM: Design of a 32-kbit synchronous SRAM with 32-bit words, using 180 nm process technology. Developed MATLAB scripts to evaluate architectural trade-offs between performance (using logical effort analysis) and area usage; see the source code for the HSPICE decks and MATLAB scripts that are used during architectural trade-off evaluation, and characterization of inverters for different supply voltages (VDD) and temperatures. It also includes HSPICE decks for the characterization of the 6-transistor SRAM cell for different transistor ratios, and the SRAM read and write circuitry. Co-designed and co-developed the SRAM using schematic entry in Cadence Virtuoso. Performed functional and timing verification by simulating extracted SPICE netlist in NanoSim. (at
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m_wxobs: I heard you might have some insight about creating test fixtures18:24
m_wxobs: if you have some pointers it would be greatly appreciated; sourcing the clamp down fixture and software infrastructure18:26
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MadHackerm_w: on the software side; xobs's test runner.18:33
tpbTitle: GitHub - exclave/exclave: Exclave embedded service runner (at
m_wso now I just need some pointers for the hardware side18:35
MadHackerThe clamps themselves are easily available - amazon and ebay even - but making a good fixture is a bit more complex than just the clamps.18:35
MadHackerPogo-pins are no fuss to get either, if you want to DIY it.18:35
MadHackerBut getting it right as opposed to "it kinda works" takes a bit of experimentation.18:36
m_wI have made a simple fixture with pogo pins before18:36
m_wfor LoFive18:36
m_wbut it use 3D printed parts and eventually it broke18:37
m_wI want something a bit more rugged for the base18:37
MadHackerLaser cut and/or CNC'd acrylic is the usual preference.18:37
MadHackerAlthough heavy paxolin is nice too.18:37
m_wwonder how much of these fixtures is custom?18:38
MadHackerWell, the box at the bottom is sometimes a generic project/electrical box milled out.18:39
MadHackerThe upright structure is the same for most similar jigs, so it's probably not exactly custom, but it's not off-the-shelf.18:39
MadHackerThat particular one has nice linear slides on the verticals; it's common just to use slots in the uprights as guides.18:40
m_wyeah I just need a good starting point18:44
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