dual EdgeTPU with lattepanda alpha

Would you like to see more information or a tutorial about how to do something with LattePanda Alpha or Delta? Post requests here!

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nik
Posts: 3
Joined: Sat Mar 02, 2019 5:43 pm

Sat Feb 06, 2021 12:36 am

hello, I'm developing a robotic platform built around a Lettapanda alpha 864.
I needed something to offload some of the vision related workload from the cpu so I bought a dual EdgeTPU from https://coral.ai/products/m2-accelerator-dual-edgetpu.
after following the provided instructions correctly it worked just fine except that only one of the two onboard accelerators shows up from lspci.
the specs located here: https://coral.ai/products/m2-accelerator-dual-edgetpu state that:
* Although the M.2 Specification (section 5.1.2) declares E-key sockets provide two instances of PCIe x1, most manufacturers provide only one. To use both Edge TPUs, be sure your socket connects both instances to the host.
is this the case for the lattepanda alpha 864? is it possible to review a part of the PCI-E schematic to make sure both lanes are connected?
here's the datasheet for the board I own: https://coral.ai/static/files/Coral-M2- ... asheet.pdf
thank you in advance

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ccs_hello
Posts: 740
Joined: Sat Oct 13, 2018 9:16 pm

Sat Feb 06, 2021 3:47 am

The link M.2 key-E module needs two independent PCIe 1-lane signals. That is, 2 copies of PCIe x1.
While LP Alpha's, per spec, is just 2-lane (or just 1-lane used) PCIe bus, a.k.a. PCIe x2.
In another word, I do not have high findent that extra signals required for 2 times (PCIe x1) are exposed on LP Alpha's key-E slot.

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jimdinunzio
Posts: 1
Joined: Mon Mar 01, 2021 1:31 am

Mon Mar 01, 2021 1:33 am

Hi,
Does this capability exist on the LattePanda Delta?

Also, I have mounted the board and it is working, but there is no securing screw hole for 30mm length, only 80mm length. The Coral Dual Edge TPU is 30mm long. The board is therefore unsecured and due to the spring in the socket hanging off at a 45 degree angle.
I looked on the internet but could not find a E-KEY 30mm to 80mm adapter. Please advise if

a) I really need to secure it.
b) where to get the right part.

Jim

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ccs_hello
Posts: 740
Joined: Sat Oct 13, 2018 9:16 pm

Mon Mar 01, 2021 6:02 pm

Jim,

Glad it works out.
You may use (if Windows) HWINFO64 or (linux) lspci -vv
to see these two Coral devices live off two separate PCIe root.

re: LP Delta
I'd say it's YMMV for the same reason I stated in post #2.
(Official documentation stated supports PCIe 2x, never said 2 times PCIe x1.
Latter has extra PCIe clock line, etc. signals.)

re: fitting short module into long open slot.
Frequently used method is to 3D print an adapter (check eBay also) or
just cut a long-hard plastic strip (one end screws into the existing mother board mounting hole; and the other end, press down the short module by its edge...)

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ccs_hello
Posts: 740
Joined: Sat Oct 13, 2018 9:16 pm

Mon Mar 01, 2021 7:21 pm

Example:
https://www.ebay.com/itm/NGFF-M-2-NVME- ... 3465894653
Length Extended Adapter.jpg
Length Extended Adapter.jpg (25.13 KiB) Viewed 819 times

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