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The Hi3519 Hisilicon CPU has RGMII pins. We are trying to connect it to the EC21 LTE Module from Quectel which contains SGMII pins. Would using two Realtek RTL8201F-VB-GG PHY chips with magnetics between them work as shown below?

EC21 (SGMII pins) <--> RTL8211DN PHY <--> MAGNETIC <--> RTL8211DN PHY <--> MAC Hi3559A (RGMII pins)

Can the PMD pins be connected directly without the magnetics? We are very limited in space so we not sure if a transformer can fit with in the design. Are there any other ways to convert between SGMII and RGMII? Thank you in advance for the help.

Edit: I just read up on the Reaktek app note and it suggest ideas on capacitive coupling to go magnetic-less: Youtronics App Note

RTL8208B supports SMII, can I use two of those PHY and connect them as shown below with capacitive coupling instead of using a transformer to save space? The new connections would be:

EC21 (SGMII pins) <--> RTL8208B PHY <--> capacitive coupling <--> RTL8208B PHY <--> MAC Hi3559A (RGMII pins)

enter image description here

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  • \$\begingroup\$ Why not usb host or uart? \$\endgroup\$ Commented Sep 30, 2019 at 21:29
  • \$\begingroup\$ Hi P__J__, can you elaborate further on what you mean by the usb host or uart? \$\endgroup\$
    – k051819
    Commented Sep 30, 2019 at 21:48
  • \$\begingroup\$ Quectelec21 Has Interfaces UART × 2 : Main UART and Debug UART USB x 1: USB 2.0 with High Speed up to 480Mbps (U)SIM x 1: 1.8V/3.0V (U)SIM Interface Digital Audio through PCM Interface (Optional) NETLIGHT × 2 : NET_STATUS and NET_MODE ADC × 2 SDIO × 2 (for Wi-Fi and SD Card) RESET (Active Low) PWRKEY (Active Low) Solder Pads for Primary, Rx-diversity and GNSS. . Configure CPU as is host and tall to the modem \$\endgroup\$ Commented Sep 30, 2019 at 22:01
  • \$\begingroup\$ Is this all on the same PCB? \$\endgroup\$
    – Voltage Spike
    Commented Sep 30, 2019 at 22:14
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    \$\begingroup\$ We need to transfer high speed data captured by the Hi3519 CPU using the LTE module to a server, I believe we need the SGMII signals to transfer to such data. Voltage Spike- Yes, it's all on the same PCB. \$\endgroup\$
    – k051819
    Commented Sep 30, 2019 at 22:23

1 Answer 1

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Serial requires transceivers and restructuring of the serial data to slower parallel data streams, which means you need logic.

An Marvell Alaska 88E1512 might work, it claims you can go from SGMII to RGMII.

EC21 (SGMII pins)<--> 88E1512 <--> Hi3559A (RGMII pins)

Which is a lot simpler than using two phys to translate.

enter image description here

Source: https://www.marvell.com/transceivers/assets/Alaska_88E1512-001_product_brief.pdf

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  • \$\begingroup\$ Hi Voltage Spike, we are trying to simplify the logic for easier board bring up. Do you think the 2 PHY method will work? Imagine EC21 (SGMII pins) <--> RTL8211DN PHY <--> MAGNETIC <--> RJ45 <- ETHERNET CABLE -> RJ45 <--> RTL8211DN PHY <--> MAC Hi3559A (RGMII pins). If the SGMII and RGMII sides each go to a RJ45 connector then connected together with an ethernet cable, the connection would work. The only difference we are doing is removing the two RJ45 and connecting the PHYs directly with some magnetic or capacitive coupling between the two. \$\endgroup\$
    – k051819
    Commented Oct 1, 2019 at 22:16
  • \$\begingroup\$ Are all these on the same PCB? You don't need magnetics if it's on the same PCB. Also, see the edit \$\endgroup\$
    – Voltage Spike
    Commented Oct 1, 2019 at 22:20
  • \$\begingroup\$ Thank you for the suggestions we will spend sometime to read up on the Marvell chip to see if it can work. Yes they are on the same PCB and wouldn't be very far from each other \$\endgroup\$
    – k051819
    Commented Oct 1, 2019 at 22:33
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    \$\begingroup\$ I didn't read the datasheet, but the product description specifically says its for translating SGMII to a regular MAC. I have heard of people using them for the same purpose. \$\endgroup\$
    – Voltage Spike
    Commented Oct 1, 2019 at 22:35

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