serialcables-hermes

Python API for Serial Cables PCIe Gen6 EDSFF Redriver Cards.

Overview

Hermes provides a Python interface for communicating with Serial Cables PCIe Gen6 EDSFF Redriver cards via the USB Type-C MCU CLI interface. These cards enable PCIe Gen6 (64 GT/s) signal conditioning for EDSFF (E1.S, E3.S, E3.L) SSD validation and testing.

Supported Products

• PCI6-AD-x8EDSFF-E3-H - X8 Golden Finger to X8 EDSFF (Standard)
• PCI6-AD-x8EDSFF-E3-H-Q - X8 Golden Finger to X8 EDSFF (Quarch Compatible)
• PCI6-AD-x16EDSFF-E3-H - X16 Golden Finger to X16 EDSFF (Standard)
• PCI6-AD-x16EDSFF-E3-H-Q - X16 Golden Finger to X16 EDSFF (Quarch Compatible)

Installation

pip install serialcables-hermes

For development:

pip install serialcables-hermes[dev]

Quick Start

from serialcables_hermes import Hermes, LoadMode

# Auto-detect device
port = Hermes.find_device()

# Connect and interact
with Hermes(port) as hermes:
    # Get device information
    info = hermes.get_version()
    print(f"Model: {info.product.model}")
    print(f"Serial: {info.product.serial_number}")
    print(f"Firmware: {info.mcu.version}")
    
    # Get card status
    status = hermes.get_status()
    print(f"Temperature: {status.thermal}")
    print(f"Fan Speed: {status.fan}")
    print(f"12V Current: {status.current}")
    
    # Detect attached EDSFF device
    detection = hermes.detect_edsff()
    print(f"EDSFF: {detection}")

Features

Redriver Tuning

Configure the PS7161 redriver ICs for optimal signal integrity:

with Hermes('/dev/ttyUSB0') as hermes:
    # Get current EQ settings
    eq = hermes.get_eq_settings()
    print(eq)
    
    # Set EQ for all chips (0-15 → 2.3-20.8 dB)
    hermes.set_eq('all', 5)  # 8.2 dB
    
    # Set EQ for specific chip
    hermes.set_eq(0, 7)  # Chip 0 to 10.3 dB
    
    # Configure flat gain (-2.8 to -0.2 dB)
    hermes.set_fg('all', 2)  # -0.8 dB
    
    # Configure transmitter swing (1050-1630 mV)
    hermes.set_sw('all', 5)  # 1490 mV
    
    # Save configuration to flash
    hermes.save_configuration()

Preset Configurations

Load optimized presets based on trace length:

from serialcables_hermes import LoadMode

with Hermes(port) as hermes:
    # Load preset for short traces (<9")
    hermes.load_configuration(LoadMode.SHORT)
    
    # Load preset for medium traces (6-9") - factory default
    hermes.load_configuration(LoadMode.MEDIUM)
    
    # Load preset for long traces (10-12")
    hermes.load_configuration(LoadMode.LONG)

EDSFF Sideband Control

Control EDSFF sideband signals:

from serialcables_hermes import Channel, DualPortState, LEDState, PowerDisableLevel

with Hermes(port) as hermes:
    # Send PERST# (30ms pulse)
    hermes.send_perst()  # Both channels
    hermes.send_perst(Channel.A)  # Channel A only
    
    # Control dual port mode
    hermes.set_dual_port(DualPortState.ON)
    
    # Control power disable
    hermes.set_power_disable(PowerDisableLevel.LOW)  # Enable power
    
    # Control host LED (amber)
    hermes.set_host_led(LEDState.ON)

I2C/SMBus Access

Direct I2C access to devices on the EDSFF connector:

with Hermes(port) as hermes:
    # Read 8 bytes from address 0xD4, starting at register 0
    result = hermes.i2c_read(0xD4, 8, register=0)
    print(f"Data: {result.data}")
    
    # Write data
    hermes.i2c_write(0xD4, [0x00, 0xFF])

Diagnostics

Run built-in diagnostics:

with Hermes(port) as hermes:
    # Run Built-In Self Test
    bist = hermes.run_bist()
    print(f"BIST: {'PASS' if bist.all_passed else 'FAIL'}")
    
    for device in bist.devices:
        print(f"  {device}")
    
    # Get complete system info
    sysinfo = hermes.get_system_info()
    print(sysinfo)

Command Line Interface

Hermes includes a CLI for quick access:

# List available ports
hermes list

# Show device info
hermes -p /dev/ttyUSB0 version
hermes -p /dev/ttyUSB0 status
hermes -p /dev/ttyUSB0 sysinfo

# Get/set EQ
hermes -p /dev/ttyUSB0 eq                  # Show current settings
hermes -p /dev/ttyUSB0 eq all 5            # Set all chips to step 5
hermes -p /dev/ttyUSB0 eq 0 7              # Set chip 0 to step 7
hermes -p /dev/ttyUSB0 eq --help-values    # Show value table

# Control EDSFF
hermes -p /dev/ttyUSB0 detect
hermes -p /dev/ttyUSB0 perst
hermes -p /dev/ttyUSB0 dual on
hermes -p /dev/ttyUSB0 hled on

# Save configuration
hermes -p /dev/ttyUSB0 save

# JSON output
hermes -p /dev/ttyUSB0 -j status

API Reference

Value Tables

EQ (Equalization) Steps:

Step	dB Value
0	2.3 dB
1	3.2 dB
2	4.3 dB
3	5.4 dB
4	7.2 dB
5	8.2 dB
6	9.5 dB
7	10.3 dB
8	12.0 dB
9	13.0 dB
10	13.9 dB
11	14.6 dB
12	16.3 dB
13	18.6 dB
14	19.9 dB
15	20.8 dB

Flat Gain Steps:

Step	dB Value
0	-2.8 dB
1	-2.0 dB
2	-0.8 dB
3	-0.2 dB

Swing Steps:

Step	mV Value
0	1050 mV
1	1150 mV
2	1270 mV
3	1380 mV
4	1460 mV
5	1490 mV
6	1600 mV
7	1630 mV

Hardware Connection

Connect to the redriver card using a USB Type-C cable to the CN3 connector. This provides access to the MCU CLI for configuration and monitoring.

For Quarch-compatible models (-QA suffix), additional connectors (J3/J4/CN4/CN5) are available for Quarch PAM integration.

Requirements

• Python 3.9+
• pyserial >= 3.5
• USB Type-C cable
• Serial Cables PCIe Gen6 EDSFF Redriver Card

License

MIT License - see LICENSE for details.

Support

• Email: support@serialcables.com
• Website: https://www.serialcables.com
• Documentation: https://github.com/serialcables/serialcables-hermes

See Also

• serialcables-atlas3 - Atlas3 PCIe Switch API
• serialcables-hydra - HYDRA JBOF API