| Products > Test Equipment |
| A High-Performance Open Source Oscilloscope: development log & future ideas |
| << < (60/71) > >> |
| nctnico:
I've ordered Jetson stuff from Arrow and they forward the order to the local branch. Works quite good. Passive heatsinking is doable. IIRC the Xavier sits around 25W tot 30W. A 20-ish by 10-ish centimeter heatsink with wide spaced fins to allow convection cooling does the job OK. 'My' Jetson TX2 project uses such a passive heatsink with a thermal design target of 60 degrees ambient for a 20W power dissipation (and some thermal headroom to spare). Where it comes to PCI-express routing it is a matter of getting the differential pairs right with phase shift corrections to account for bends being shorter / longer. How difficult that is to achieve depends on the PCB package you are using. If it has differential phase matching it is not difficult. At the FPGA side it should be a matter of setting up the core and dropping it into the design. From there it should pop-up in the PCI tree of the Linux kernel. From the software side use memmap to map the PCI express memory areas into user space and you can talk to the FPGA. Unless there is a realtime requirement to handle something from software, a driver may not be necessary. Where it gets hairy is to enable / disable caching and to have the FPGA push data into the processor's memory space but when the acquisition memory is attached to the FPGA that may not be necessary. |
| tom66:
Unfortunately, I veto ordering from Arrow due to a prior total screwup with them that cost me weeks of my time and chasing them for refunds as they totally misunderstood DDP incoterms, actually for this very project. Digi-Key do have stock and they've never done me wrong. Memory mapping should be fine then. I would assume the process would need to have permission to access PCI devices, though? Does it need to be in a PCI group or run as root/thru sudo? PS. Not worried about differential routing. The DDR3 memory on the prototype was the hardest part. CSI-2 bus was comparably easy. CAD tools, it's all CircuitMaker/Altium. Am considering whether I should move to KiCad though to keep tools open. |
| Hydron:
Arrow seems to now have dropped the DDP option for UK shipments altogether, probably due to the clusterfuck that is Brexit making it harder to do. Means that it's uneconomic to buy from them now anyway as they tend to ship multiple packages per order, each of which FedEx will bill you £12 for handling the VAT payment on. Having similar issues buying from some other suppliers too, shame all the pain can't be reserved for the people who bought into the lies back in 2016 😡. As for the Jetson, you may be interested in the open source antmicro Jetson carrier board - they have their Altium design files up on GitHub. Might save some time, even if it's just nabbing footprints etc. from it. |
| nctnico:
--- Quote from: tom66 on January 02, 2021, 11:28:35 pm ---Memory mapping should be fine then. I would assume the process would need to have permission to access PCI devices, though? Does it need to be in a PCI group or run as root/thru sudo? --- End quote --- Root rights are enough. From the OS point of view you are mapping a piece of physical memory into a user space process. Something to look out for is to tell memmap to mark the memory as uncacheable. --- Quote ---PS. Not worried about differential routing. The DDR3 memory on the prototype was the hardest part. CSI-2 bus was comparably easy. CAD tools, it's all CircuitMaker/Altium. Am considering whether I should move to KiCad though to keep tools open. --- End quote --- I'd stick to Altium for now. The costs for producing a prototype are so high that it is unlikely many people will be changing the layout and if they do they might want a completely different form factor and start from scratch. |
| free_electron:
If you need layout help ... or a second pair of eyes. ping me. |
| Navigation |
| Message Index |
| Next page |
| Previous page |