STEMlab 125-14 X-Channel System (Discontinued)

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Overview

The Red Pitaya X-Channel system is a multi-board configuration built from STEMlab 125-14 LN devices connected in a daisy-chain via SATA cables. One board acts as the Primary (unmodified) and provides the master clock and trigger signals. The remaining boards are Secondary boards, hardware-modified so that their ADC clock is driven from the SATA connector rather than the on-board oscillator, enabling phase-coherent operation across all channels.

Note

This is the original X-channel system configuration. For X-channel 2.0 (Click Shields), see the


System Components

The X-Channel system consists of:

  • One Primary Low-Noise STEMlab 125-14 - A standard Low-Noise STEMlab 125-14 device that provides clock and trigger signals to Secondary devices

  • One or more Secondary Low-Noise STEMlab 125-14 devices - Modified devices that receive clock and trigger signals from the Primary device and can distribute them to the next Secondary device (marked with an “S” sticker)

  • SATA synchronisation cables - For connecting boards in a daisy-chain configuration

  • Software - Supports multi-channel RF signal acquisition and generation


Features

  • Scalable multi-channel acquisition: 2 inputs per board (4, 6, 8+ channels possible)

  • Phase-coherent operation: All boards share the same clock and trigger

  • Linear power supplies: Reduced noise for high-quality measurements

  • Daisy-chain topology: Simple connection via SATA cables

  • Software support: Multi-channel acquisition and generation applications

  • Standard STEMlab 125-14 LN specifications per board


Quick Reference

Category

Key Specifications

Channels per board

2 input + 2 output channels

ADC

2 channels, 14-bit, 125 MS/s (per board)

DAC

2 channels, 14-bit, 125 MS/s (per board)

Synchronisation

SATA daisy-chain, shared clock & trigger

System scalability

Multiple boards (4, 6, 8+ channels)

Special Features

Phase coherence, Low noise, Multi-channel

Hardware Configuration & Differences

Primary Board

The Primary board is a standard STEMlab 125-14 LN used without any hardware modification. It:

  • Provides the master clock signal via its on-board oscillator

  • Distributes the clock and trigger to Secondary boards via the SATA connectors

Secondary Boards

Secondary boards are STEMlab 125-14 LN boards with a single hardware modification (identified by an “S” sticker):

Parameter

STEMlab 125-14 LN (Primary)

STEMlab 125-14 LN Secondary

ADC clock source

On-board oscillator (default)

SATA connector (from Primary/previous board)

Resistors R25, R26

In default position

Relocated to R27, R28

External ADC clock

No

Yes (from SATA daisy-chain)

Operation without SATA clock input

Normal (uses on-board oscillator)

FPGA non-functional; PS boots from 33 MHz

Identification

No marking

“S” sticker on the board

Note

Secondary boards cannot be used as standalone boards without an external clock source or relocating the resistors back to the original positions.


Synchronisation

The X-Channel system uses:

  • Shared clock: Distributed from Primary through SATA daisy-chain

  • Shared trigger: Synchronized trigger signals via SATA connectors

  • SATA cables: Up to 500 Mb/s data rate for clock/trigger distribution

For detailed synchronisation information, see:


Technical Specifications

Each board in the X-Channel system has the same specifications as the STEMlab 125-14 Low Noise board.

For full technical specifications, please refer to the STEMlab 125-14 LN specifications.

See also

For more detailed information, please refer to the Original Gen board comparison table.


Performance & Measurements

Note

Although we do not have specific measurements for the STEMlab 125-14 LN boards in X-Channel configuration, the performance of the fast analog inputs is the same as for STEMlab 125-14. The output performance is covered in Leonhard Neuhaus’s blog about Red Pitaya DAC performance (measurements with added linear power supplies).

You can find reference measurements here:


FAQs

Can a different Red Pitaya STEMlab 125-14 unit be used as a primary device?

Yes, you can use any version of the STEMlab 125-14 as the Primary device. This includes:

  • STEMlab 125-14 LN

  • STEMlab 125-14

  • STEMlab 125-14 Z7020

However, for best performance, it is recommended to use the STEMlab 125-14 LN as the Primary device for its improved noise characteristics.

Can I use X-Channel Secondary boards standalone?

No, Secondary boards are hardware-modified to receive an external clock and cannot operate standalone without:

  1. An external clock source, or

  2. Relocating the SMD resistors back to the original positions (reversing the modification)


Additional Resources

For additional specifications and setup information, please refer to: