SFP Media Buddy

Tested Devices

The following devices have been tested and confirmed to work or not work

Device	SFP	Uart	Comments
Was-110	Yes	Yes
HLX-SFP	Yes	No	Uart pins not on SFP pins
G-010S-P	Yes	Yes
DFP-34x-2c2	No	No	Currently working on new firmware to support SFP, Pulls significant power, v1 of hardware may not support properly. Devices have internal uart headers not exposed to SFP

How to use a media buddy

The Media Buddy should be plug and play for standard usage. Plug into a USB-C wall wart or port supplying at least 1 amp of power at 5v, insert your SFP module, and plug in a RJ45 cable the to ethernet port. If you need to access the SFP device or modify configurations then you will need to plug it into a computer. Whenever you plug your media buddy into your computer it should expose a single device with 4 functions.

2 Serial Devices

1 HID Device

1 Unknown Device

Windows

Whenever connected 4 devices will show within windows with only 3 being currently used. From device manager you can see a HID device, a unknown I2C device and two COM ports. The COM ports are of interest here, while the order appears to be random they are used to control both the SFP module within the device and the device itself.

With the device connected you can now use PuTTY or your favorite serial program to connect to the device or SFP module. While the order is random it will stay constant while plugged in. As an example I have opened putty and set the connection type to Serial and then put in the Serial Line field COM3 which I grabbed from device manager. Finally I set the baud rate to 115200 which is a common baud rate for these serial devices.

If you successfully connect to the SFP stick you should start to see text streaming as you can see below, if its been awhile try power cycling the stick with the SFP power button or the cycle_sfp command in the media buddy interface. If this still does not work check that you are using the correct pins for your device.

If you picked the wrong COM interface you will just see the media buddy command console as seen below, you can just select the other COM port and reconnect

Linux

<coming soon>

Mac

<coming soon>

Hardware

The SFP Media buddy is a 2.5G Media converter containing a rp2040 for management and a RTL8221B for media conversion. Power is provided by a USB-C interface that supports USB-PD including all current ranges and voltages of 5v, 9v, and 15v. The incoming power is then converted to 3.3v for usage by the media converter, rp2040, and SFP socket, the onboard converter is capable of 3 amps of current at 3.3v which should be plenty for all currently known SFP modules.

The above figure labels all the important components of the media buddy. Starting from top left and moving right and then down there is a button to power cycle the SFP port, status LEDs for sufficient power, command connection, and SFP link established. Next row is the Eeprom for storing config data and then the rp2040 which acts as management controller. Next is the External UART for using the media buddy as a simple usb-uart converter followed by breakouts for all of the SFP control pins allowing one to check their status externally. Next is the RTL8221B media converter IC followed by a 3.3v fan header.

For power input there is a USB-C port that supports USB-PD as well as an unpopulated barrel plug that supports any voltage from 5-20v. If you want to populate the barrel plug it is part number SameSky/CUI PJ-063AH

A defining feature of the SFP Media Buddy that sets it apart from other 2.5G media converters on the market is its management features. While it doesn’t allow for typical networking management features such as VLANs, it does allow for control over the RTL8221B registers as well as accessory pins of the SFP socket. This allows one to power cycle the SFP over the USB console or toggle pins on the SFP socket as well as reset the RTL8221B. One benefits of this is also the ability to access non-standard TTL pins on SFP modules over a secondary console over USB.

Overall the USB interface three interfaces are exposed

USB console(0) tied to the PIO UART of the RP2040

USB console(1) is a virtual management console, commands are documented below

Custom I2C interface <Driver in development>

Firmware

Updates to the firmware are available by calling the update_fw function and dragging new uf2 file onto the exposed mass storage device If you cannot get to the command console directly attempting to open the console as a baud rate of 1200 should also put it in mass storage mode.

Latest Firmware

Commands

Commands one can run on the SFP Media Buddy’s console

i2cget

gets 1 or more bytes from a i2c address

i2cget[CHIP-ADDRESS] [DATA-ADDRESS] [LEN]

Arguments

CHIP-ADDRESS

DATA-ADDRESS

LEN

i2cset

… sets 1 or more bytes to a i2c

i2cset[CHIP-ADDRESS] [DATA-ADDRESS] [DATA]

Arguments

CHIP-ADDRESS

DATA-ADDRESS

DATA

mdio_write

sets the register to value

mdio_write[MMD] [REGISTER] [VALUE]

Arguments

MMD

REGISTER

VALUE

mdio_read

reads the register

mdio_read[MMD] [REGISTER]

Arguments

MMD

REGISTER

set_rx_pin

Sets the rx pin for uartrn Valid values are 0-9 with 2-9 being pins on the SFP socket

set_rx_pin[PIN]

Arguments

PIN

set_tx_pin

Sets the tx pin for uartrn Valid values are 0-9 with 2-9 being pins on the SFP socket

set_tx_pin[PIN]

Arguments

PIN

rtl_reset

Resets media converter IC

rtl_reset

rtl_set_serdes_mode

Set the mode of the media converter.rn 1 for manual rn 2 for autorn any other entry resets

rtl_set_serdes_mode

rtl_clear_serdes_mode

Reset the mode of the media converter to default values(auto)

rtl_clear_serdes_mode(auto)

Options

valuesauto

rtl_set_eth_speed

Set the speed of the ethernet port.rn 1 for 10M rn 2 for rn 100Mrn 3 for 1Grn 4 for 2.5grn any other entry resets

rtl_set_eth_speed

rtl_clear_eth_speed

Reset speed of ethernet to default values(auto negotiate)

rtl_clear_eth_speed(auto negotiate)

Options

valuesauto

rtl_get_info

Get the current speed and link status of the media converter

rtl_get_info

rtl_get_leds

Get the current led status

rtl_get_leds

enable_sfp

Enables power to the SFP Module

enable_sfp

disable_sfp

Disables power to the SFP Module

disable_sfp

cycle_sfp

Power cycles the SFP Module

cycle_sfp

update_fw

reboots device into msc flash mode

update_fw

pin_info

outputs current state of SFP pins

pin_info

version

get SFP-BUDDY version

version

help

prints help for commands

help