5 ms·

I'll give $20 to the first person who gets one of these cards & sets up a host with Non-Transparent Bridging (NTB, effectively making that PCIe slot look like a

I'll give $20 to the first person who gets one of these cards & sets up a host with Non-Transparent Bridging (NTB, effectively making that PCIe slot look like a device), and connects & talks to the Pi.

jacquesm 4y ago
You're cheap ;)
geerlingguy 4y ago
Supposedly the folks at Timebeat are working on a similar card[1], but one that appears as a PCIe device with two serial ports—one through to a Raspberry Pi, and one through to a U-blox module for timekeeping. [1] https://store.timebeat.app/products/ocp-tap-timecard-mini-platinum-edition https://store.timebeat.app/products/ocp-tap-timecard-mini-pl...
- rektide 4y ago
  Woof $1200! But for a very neat application, certainly, that certainly vendors would have been charging a lot more for in the past. And it includes the $100 LEA-M8F GPS module... And the $150 SiTIME SiT5721 oxco over controlled oscillator. Excellent parts. I was going to ask if the Pi had decent ptp support to actually be useful speaking ethernet, but you've already answered that (yes), https://www.jeffgeerling.com/blog/2022/ptp-and-ieee-1588-hardware-timestamping-on-raspberry-pi-cm4 https://www.jeffgeerling.com/blog/2022/ptp-and-ieee-1588-har... I do kind of wish it had a PCIe ethernet controller onboard for the host too, also with ptp tied to the host. Sending that fine timing data across serial & PCIe bused to the host & to the hosts card feels unideal, like a source of some jitter, but maybe it's not really an issue.
  - namibj 4y ago
    PCIe has a continuous 100MHz clock if you don't utilize link parking power be saving mechanisms. The device should be able to lock to the host's base clock that way, and phase offsets should be something you can resolve by measuring. Ideally computers would support consuming a PLL reference via 1GBASE-T, as that already has a need for a locked clock for TX and RX near-side cross-talk compensation, and CERN demonstrated usage of this for clock carrier distribution in their GPS-shielding tunnels. OFC integrated with PTP to accurately sync time; AFAIK they did for ns-accurate event time stamp assignment in some distributed sensor networks.

jacquesm 4y ago

You're cheap ;)

geerlingguy 4y ago

Supposedly the folks at Timebeat are working on a similar card[1], but one that appears as a PCIe device with two serial ports—one through to a Raspberry Pi, and one through to a U-blox module for timekeeping. [1] https://store.timebeat.app/products/ocp-tap-timecard-mini-platinum-edition https://store.timebeat.app/products/ocp-tap-timecard-mini-pl...

rektide 4y ago
Woof $1200! But for a very neat application, certainly, that certainly vendors would have been charging a lot more for in the past. And it includes the $100 LEA-M8F GPS module... And the $150 SiTIME SiT5721 oxco over controlled oscillator. Excellent parts. I was going to ask if the Pi had decent ptp support to actually be useful speaking ethernet, but you've already answered that (yes), https://www.jeffgeerling.com/blog/2022/ptp-and-ieee-1588-hardware-timestamping-on-raspberry-pi-cm4 https://www.jeffgeerling.com/blog/2022/ptp-and-ieee-1588-har... I do kind of wish it had a PCIe ethernet controller onboard for the host too, also with ptp tied to the host. Sending that fine timing data across serial & PCIe bused to the host & to the hosts card feels unideal, like a source of some jitter, but maybe it's not really an issue.
- namibj 4y ago
  PCIe has a continuous 100MHz clock if you don't utilize link parking power be saving mechanisms. The device should be able to lock to the host's base clock that way, and phase offsets should be something you can resolve by measuring. Ideally computers would support consuming a PLL reference via 1GBASE-T, as that already has a need for a locked clock for TX and RX near-side cross-talk compensation, and CERN demonstrated usage of this for clock carrier distribution in their GPS-shielding tunnels. OFC integrated with PTP to accurately sync time; AFAIK they did for ns-accurate event time stamp assignment in some distributed sensor networks.