Sfp

Platform-universal Arduino library for reading SFP/SFP+ diagnostics (SFF-8472 style) over I2C.

What it provides

• A0h identity parsing (vendor, PN, SN, date, compliance bytes)
• A2h live DOM telemetry:
  • temperature (°C)
  • Vcc (V)
  • TX bias (mA)
  • TX power (mW / dBm)
  • RX power (mW / dBm)
• Alarm/warning thresholds
• Live flag words
• Internal and external calibration handling
• Raw EEPROM access and hex dumps
• SFP+ upper-page helpers:
  • selectUpperPage(page)
  • readA2Paged(page, offset, buffer, len)
  • readUpperPage00..03()
  • decodeUpperPageLinkCodes()

Platform support

Uses only standard Arduino TwoWire (Wire). Designed for AVR, SAMD, ESP32, RP2040, STM32, and other cores with normal Wire support.

Installation

1. Copy this folder into your Arduino libraries directory.
2. Restart Arduino IDE.
3. Include the library:

#include <Wire.h>
#include <Sfp.h>

Wiring and pinout

Required signals (minimum)

• VCC (3.3V)
• GND
• MOD_DEF1 / SCL
• MOD_DEF2 / SDA

Optional but useful:

• TX_DISABLE (control)
• TX_FAULT (status)
• RX_LOS (status)
• MOD_DEF0 / ABS (presence detect)

Generic connection example

SFP cage/module          MCU
---------------------------------------------
VCC_T (+3.3V)       ->   3V3
VEE_T (GND)         ->   GND
VCC_R (+3.3V)       ->   3V3
VEE_R (GND)         ->   GND
MOD_DEF1 (SCL)      ->   I2C SCL
MOD_DEF2 (SDA)      ->   I2C SDA
TX_DISABLE          ->   GPIO output (optional)
TX_FAULT            ->   GPIO input (optional)
RX_LOS              ->   GPIO input (optional)
MOD_DEF0 / ABS      ->   GPIO input (optional)

RP2040 Pico example

Important: SFP TX/RX data path vs I2C diagnostics

• Do not connect SFP high-speed differential lines directly to Pico GPIO/UART pins.
• SFP TD+/TD- and RD+/RD- are high-speed analog differential pairs (SerDes level), not TTL UART.
• Pico can connect directly only to:
  • I2C diagnostics (MOD_DEF1/SCL, MOD_DEF2/SDA)
  • control/status pins (TX_DISABLE, TX_FAULT, RX_LOS, optional MOD_DEF0/ABS)
• For actual payload transport over fiber, use a dedicated PHY/SerDes/media converter in the data path.

So in this library:

• Pico ↔ SFP is for monitoring/control via I2C
• Optical TX/RX payload is handled by external hardware path

RP2040 Pico pin       SFP signal
----------------------------------
3V3(OUT)          ->  VCC_T + VCC_R
GND               ->  VEE_T + VEE_R
GP5 (I2C0 SCL)    ->  MOD_DEF1 / SCL
GP4 (I2C0 SDA)    ->  MOD_DEF2 / SDA
GP6 (output)      ->  TX_DISABLE (optional)
GP7 (input)       ->  TX_FAULT (optional)
GP8 (input)       ->  RX_LOS (optional)
GP9 (input)       ->  MOD_DEF0 / ABS (optional)

Wire.setSDA(4);
Wire.setSCL(5);
Wire.begin();
Wire.setClock(100000);

ESP32 example

ESP32 pin            SFP signal
----------------------------------
3V3              ->  VCC_T + VCC_R
GND              ->  VEE_T + VEE_R
GPIO22 (SCL)     ->  MOD_DEF1 / SCL
GPIO21 (SDA)     ->  MOD_DEF2 / SDA
GPIO19 (output)  ->  TX_DISABLE (optional)
GPIO18 (input)   ->  TX_FAULT (optional)
GPIO5  (input)   ->  RX_LOS (optional)
GPIO17 (input)   ->  MOD_DEF0 / ABS (optional)

Wire.begin(21, 22); // SDA, SCL
Wire.setClock(100000);

Electrical notes (essential)

• SFP modules require a stable 3.3V supply (not 5V).

• Budget enough current on 3.3V rail:

  • typical optical modules: often ~150–300 mA
  • some modules can draw more during startup/laser activity

• Decouple near the cage/module power pins (for example 100 nF + 10 µF close to the connector).

• Tie all grounds together (MCU + SFP power ground).

• SFP I2C is typically 3.3V logic.

• SDA/SCL usually need pull-ups to 3.3V:

  • common values: 2.2k–4.7k
  • if your breakout already has pull-ups, do not add too-strong parallel pull-ups

• If MCU is 5V-only, use proper level shifting for I2C and status/control GPIOs.

• Keep wiring short and clean for reliable I2C.

• If reads are unstable, lower I2C clock (e.g., 100 kHz) and re-check power integrity.

Basic usage

#include <Wire.h>
#include <Sfp.h>

sfp::Sfp sfpMod;

void setup() {
  Serial.begin(115200);
  Wire.begin();
  Wire.setClock(100000);

  if (sfpMod.begin(Wire, 0x50, 0x51) != sfp::Error::Ok) {
    Serial.println("SFP init failed");
    while (1) {}
  }

  sfp::Identity id;
  sfp::DomData dom;
  if (sfpMod.readAll(id, dom) == sfp::Error::Ok) {
    Serial.print("Vendor: "); Serial.println(id.vendor);
    Serial.print("PN: "); Serial.println(id.partNumber);
    Serial.print("Temp C: "); Serial.println(dom.temperatureC, 2);
    Serial.print("RX dBm: "); Serial.println(dom.rxPowerdBm, 2);
  }
}

void loop() {}

Example outputs

Identity + DOM

=== SFP Identity ===
Vendor: FINISAR
PN: FTLF1318P3BTL
SN: FNS1234567A
DOM implemented: yes
Int cal: yes
Ext cal: no
--- DOM ---
Data ready: yes
Temp [C]: 36.75
Vcc [V]: 3.2991
TX bias [mA]: 6.120
TX power [mW]: 0.8123 / [dBm]: -0.90
RX power [mW]: 0.6550 / [dBm]: -1.84
TX fault: 0
RX LOS: 0

Thresholds + flags

--- Thresholds ---
Temp HA/LA/HW/LW: 85.00 / -10.00 / 75.00 / -5.00
Vcc  HA/LA/HW/LW: 3.60 / 3.00 / 3.50 / 3.10
TXB  HA/LA/HW/LW: 12.00 / 2.00 / 10.00 / 3.00
TXP  HA/LA/HW/LW: 1.58 / 0.10 / 1.26 / 0.13
RXP  HA/LA/HW/LW: 1.58 / 0.05 / 1.26 / 0.08
Flags temp/vcc/txb/txp/rxp: 0x0000 0x0000 0x0000 0x0000 0x0000

API summary

• begin(wire, a0Addr=0x50, a2Addr=0x51)
• readIdentity(Identity&)
• readDom(DomData&)
• readThresholds(Thresholds&)
• readFlags(Flags&)
• readAll(Identity&, DomData&, Thresholds* = nullptr, Flags* = nullptr)
• readA0(offset, buf, len) / readA2(offset, buf, len)
• dumpA0(stream, start, len, cols) / dumpA2(...)
• selectUpperPage(page)
• readA2Paged(page, offset, buf, len)
• readUpperPage00..03(...)
• decodeUpperPageLinkCodes(LinkCodes&)

Included examples

• examples/basic_dom/basic_dom.ino — identity + live DOM polling
• examples/sfp_plus_pages/sfp_plus_pages.ino — upper-page reads and link code decode
• examples/identity_thresholds/identity_thresholds.ino — identity, thresholds, and flags report
• examples/usb_serial_sfp_bridge/usb_serial_sfp_bridge.ino — transparent USB↔UART bridge with SFP diagnostics monitoring; LED blinks on SFP errors
• examples/rp2040_pio_manchester_serial/rp2040_pio_manchester_serial.ino — RP2040 PIO Manchester TX/RX character bridge (for hardware with external differential interface)

Error handling

All functions return sfp::Error. Common non-OK values:

• NotInitialized
• I2cNack
• BadParam
• DomNotSupported
• DataNotReady

Compatibility note

Different SFP vendors expose diagnostics differently. Some modules provide partial or vendor-specific behavior. Validate against your exact transceiver models.