[BPI-R64] Possible hardware improvements

PCIe slots:

Because most of newer 5G/LTE modems are using M.2 B-key interface, it would be nice to have alternative M.2 B-key slot in addition to mPCIe connector.

One possibility would be adding extra M.2 B-key slot in bottom side of board. User then could select which one to use. Only one of them can be used same time.

Newer 5G modems are using PCIe instead of USB connection. Most of mPCIe to M.2 B-key adapters does not have PCIe lines connected. Having possibility to connect modem without any adapter would be great.

Also adding second SIM-card and M.2 B-key slot would allow to use two modems at same time. Second M.2 B-key slot would not need USB and it would be PCIe only.

Current design limits MiniPCIe slots 3.3V current to 1.5A which is not enough for all 5G/LTE modems. SY6280AAC would allow max. 2A which might be just enough for load spikes. It might be good idea to change switch something which allows 2.5-3A loads. Or at least change current setting to 2A.

eMMC:

Some of use cases are not using eMMC at all. So it would be great to have an option to order board without eMMC to reduce cost.

Ethernet:

Dual radio AP or 5G router would benefit having 2.5GBits uplink ethernet port. I’m not aware of any mediak switch chips with 2.5Gbits ports, so having only two ports without switch would be one option. Then POE function should be connected to 2.5Gbits port instead of 1Gbits port.

hi, at least current problems need to be solved

  • missing tx capacitors on pcie
  • remove resistors for current limiting on pcie
  • fix crossed sata - lanes on pcie

btw. i got info, that mt7915 needs 3v3 3A on pcie to work properly…so imho this is the minimum that should be supported

i guess make an option without emmc is more expensive than add it to all boards

afaik 2.5G on SOC (only first gmac) is a propritary protocol that cannot be used without a mtk chip that supports it too (like switch)…i think switch is more common for a router port than have the 2 gmac alone

imho the pcie shared with sata should be the one without usb…so if you want sata, you have no pcie with USB. i guess m2 cards are not yet common enough to add a slot. but bpi-r2-pro gets one…maybe it’s a better choice for you

Just as a FYI, on the R64 v1.1 board I bought last month the current limiting capacitors were already updated to 3K for a 3.3V/2.26A current limit (above the SY6280A recommended 2A maximum limit) versus the old 4K7 for a 3.3V/1.44A current limit.

But that’s only for the 3.3V PCIe lines, not the extra 5V supplied to reserved lines 49 and 51 (and also dubiously to lines 46 WPAN and 48 +1.5V but which is generally unused) for use by BananaPi’s own wireless cards and some others such as the Unielec U7615N-L3.

The PCI-SIG specifications state a 1100mA normal and 2750mA peak current on 3.3V for minipcie.

As far as I can tell adding capacitors to stabilize peak power draws was only suggested in topic Quectel EC25: USB port connect-disconnect when on 2G so not “missing” per se.

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thanks for this information.

i got the “capacitor missing on tx lines” information from mediatek (was about a google coral card)

edit found it:

Bpi-r64 pcie slot has hw issue, so we use MTK reference board to test it before and coral card was returned to BPI already so we cannot test it again.

About r64 HW issue, we just have solution to make it stable. Maybe you can ask him to rework the board.

1.Add two 100uf capacitance

2.short pin (red circle) or change to 3K resistance to remove pcie current limit <- it’ll cause system unstable when pcie device needs more power from system

is the sata-issue fixed too (pcie too,crossed tx/rx)?

BPI-R2 Pro have M.2 E-key slot which is for wlan cards. 5G/LTE modems needs M.2 B-key slot.

I meant not to remove current mPCIe slots. Just add extra M.2 B-key slot in other side of board. Then you can select which to use. They would use same PCIe lines so both slots can’t be used same time.

It might be good idea to route USB3 signals to M.2 B-key slot instead of USB2. That would need same kind of switch as sata port have. User could disable external USB3 port and reroute signal to M.2 B-key slot. Currently some of 5G modems use USB3 and some PCIe. But all them use M.2 B-key connector.

I think current sharing PCIe/USB2 slot with SATA is good idea. You can still use USB2 LTE modem and SATA both same time. I’m currently using DW5821e with M.2 B-key adapter in shared slot and also SSD disk connected to SATA port.

Good to hear that newer boards have changed resistors to allow 3.3V/2.26A. I need to solder extra parallel resistor to get DW5821e working. Otherwise card rebooted when carrier aggregation was activated.

SY6280A could be directly replaced with SY6282ACC which is 3A version of same switch. That would allow change limit to 2750mA spec value.