u-blox Serial Port Service (SPS) Documentation

This folder contains comprehensive documentation for implementing SPS (Serial Port Service) communication with u-blox BLE modules.

What is SPS?

SPS is a proprietary u-blox protocol for wireless serial communication over Bluetooth Low Energy (BLE). It provides a "virtual serial port" with built-in credit-based flow control.

Supported Modules

Module	BLE	Wi-Fi	SPS Server	SPS Client	Notes
NORA-W36	5.3	Wi-Fi 4	✓	✓	Dual-mode (Wi-Fi + BLE)
NORA-B26	6.0	—	✓	✓	BLE-only, Central + Peripheral
NORA-B27	6.0	—	✓	—	BLE-only, Peripheral only

Note that following older geneation u-blox module also support SPS, but with another AT command set:

• ANNA-B1
• ANNA-B41
• NINA-B1
• NINA-B2
• NINA-B31
• NINA-B41
• NINA-W15
• ODIN-W2

Documentation Files

File	Description
SPS_PROTOCOL.md	Core protocol specification - service UUIDs, flow control, architecture, connection procedure
SPS_CLIENT_PYTHON.md	Python SPS Client implementation using Bleak library
SPS_SERVER_PYTHON.md	Python SPS Server implementation using bless library
SPS_CLIENT_C.md	C SPS Client implementation (pseudocode for any BLE stack)
SPS_SERVER_C.md	C SPS Server implementation (pseudocode for any BLE stack)
SPS_UBLOX_CONFIG.md	Configuring u-blox modules - AT commands, ucxclient API, transparent mode

Quick Start

If you're building a client (connecting to a u-blox module):

1. Read SPS_PROTOCOL.md to understand the protocol
2. Choose your language:
   • Python: SPS_CLIENT_PYTHON.md
   • C/Embedded: SPS_CLIENT_C.md

If you're building a server (hosting SPS service):

1. Read SPS_PROTOCOL.md to understand the protocol
2. Choose your language:
   • Python: SPS_SERVER_PYTHON.md
   • C/Embedded: SPS_SERVER_C.md

If you're configuring u-blox modules:

1. Read SPS_UBLOX_CONFIG.md for AT commands and API usage

SPS UUIDs (Quick Reference)

Service:  2456e1b9-26e2-8f83-e744-f34f01e9d701
FIFO:     2456e1b9-26e2-8f83-e744-f34f01e9d703  (data transfer)
Credits:  2456e1b9-26e2-8f83-e744-f34f01e9d704  (flow control)

Key Concepts

• SPS Server: Hosts the SPS GATT service, advertises, waits for connections
• SPS Client: Scans, connects, discovers service, exchanges data
• Flow Control: Credit-based system prevents buffer overflow
• CCCD: Must enable notifications on both FIFO and Credits characteristics

Version History

Version	Date	Changes
1.3	2026-01-22	Split into multiple files for easier navigation
1.2	2026-01-22	Added NORA-B27 support, generalized module references
1.1	2026-01-21	Added Serial Cable Replacement chapter
1.0	2026-01-20	Initial comprehensive documentation