Main MCU Firmware

Firmware for the Velo Bling-Bling project

LED lights for bicycle wheels. 16 multi color LEDs on both sides (PCB top- and bottom side). There are two windows (upper and lower) on both sides for display dynamic information like speed, trip time, trip distance, etc. or static information like strings and images. The windows have a resolution of 100 x 16 pixels. The space between the windows can be filled with a pattern/image (AKA blingbling).

Target system is a proprietary PCB (eWheel32 V1.4 an newer) with a MK22DX256VLF5 MCU from Freescale/NXP. The PCB is free hardware, see ElectronicDesign and GitHub

There is also an optional Bluetooth Low Energy (Smart) subsystem on board. It is a LAIRD BL652-SA module. The Bluetooth application software is on GitHub too.

It is possible to mount the PCB direct onto the wheel spokes but it is better to use a mounting frame. This frame can be ordered from or you can print it by yourself on 3D printer. See FrameDesign and GitHub


Peter Schmid, Switzerland,

This file is part of "Velo Bling-Bling" main MCU firmware.

"Velo Bling-Bling" firmware is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.

"Velo Bling-Bling" is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

You should have received a copy of the GNU General Public License along with "Velo Bling-Bling". If not, see


Kinetis Design Studio Integrated Development Environment (IDE)

The Kinetis Design Studio (KDS) is a complimentary integrated development environment for Kinetis MCUs that enables robust editing, compiling and debugging of your designs. Based on free, open-source software including Eclipse, GNU Compiler Collection (GCC), GNU Debugger (GDB), and others, the Kinetis Design Studio IDE offers designers a simple development tool with no code-size limitations.

You have to use an old Version (2.0.0, current is 3.2.0) for the veloblingbling project because the Processor Expert USB Stack does not work with newer Kinetis Design Studio Integrated Development Environment.

Processor Expert Software and Embedded Components

Processor Expert Software is a development system to create, configure, optimize, migrate, and deliver software components that generate source code for our (Freescale/NXP) silicon.

Unfortunately the Processor Expert USB Stack v4.1.1 NXP bare metal (no OS) USB Stack is no longer supported. But you can still find it under (ARCHIVED) USB Stack. You need a Windows PC to install, but the Processor Expert components can be used for Linux boxes too, the PEupd files are in the directory C:\Freescale\Freescale USB Stack v4.1.1\ProcessorExpert\Components and have to be imported into the KDS IDE: Processor Expert -> Import Components.

I will migrate the Velo Bling-Bling USB software from Freescale USB Stack v4.1.1 to Erich Styger's USB Stack.

Debug Adapter

The KDS supports following adapters (protocols):

  • OpenSDA Serial and Debug Adapter (proprietary Freescale/NXP/P&E Microcomputer Systems)
  • Segger (industrial standard)
  • OpenOCD,

I propose to use a Freescale/NXP Freedom Board e.g. FRDM-K22F as a debug adapter. I use the OpenOCD/CMSIS-DAP/mbed-interface protocol (factory set on FRDM-K22F).

Quote from Freedom Board for Kinetis K22F Hardware (FRDM-K22F), Users Guide

3.2.1 Debug interface

Signals with SPI and GPIO capability are used to connect directly to the SWD of the K22F. These signals are also brought out to a standard 10-pin (0.05”) Cortex debug connector (J11). It is possible to isolate the K22F MCU from the OpenSDAv2 circuit and use J11 to connect to an off-board MCU. To accomplish this, cut the trace on the bottom side of the PCB that connects J7 pin 2 to J11 pin 4. This will disconnect the SWD_CLK pin to the K22F so that it will not interfere with communication to an off-board MCU connected to J7. The J11 header is populated by default. A mating cable, such as a Samtec FFSD IDC cable, can then be used to connect from the OpenSDAv2 of the FRDM-K22F to an off-board SWD connector.

You can still use the FRDM-K22F as a prototype board. You should solder a pinheader and plug a jumper if you want to use the FRDM-K22F as a prototype board.

See also an excellent introduction to OpenOCD/CMSIS-DAP Debugging by Erich Styger.

Get the Software and Import the Project into the IDE

Get the Source from the Repository

The Velo Bling-Bling Kinetis project is on the GitHub repository Download the ZIP-File and unzip it or better clone the repository e.g. for GNU/Linux:
psi@homer:~/veloblingbling/mcu> git clone
Klone nach 'veloblingbling-mcu' ...
remote: Counting objects: 265, done.
remote: Compressing objects: 100% (97/97), done.
remote: Total 265 (delta 167), reused 260 (delta 166), pack-reused 0
Empfange Objekte: 100% (265/265), 223.50 KiB | 0 bytes/s, Fertig.
Löse Unterschiede auf: 100% (167/167), Fertig.
Prüfe Konnektivität ... Fertig.

Import the Project into the IDE

File -> Import -> General -> Existing Projects into Workspace ->
Select root directory
Copy project into workspace
Browse to veloblingbling/mcu directory

I don't know why, but I had to change the Processor Expert system directory:
Window -> Preferences -> Processor Expert -> Paths
system directory /opt/Freescale/KDS_2.0.0/eclipse/ProcessorExpert


  • Data sheets
  • Features
    • Core ARM Cortex M4, 50 MHz
    • Run mode current 17 mA, wait 8 mA
    • A/D Converter - Bits (bit) 16
    • Additional Features Vref
    • Ambient Operating Temperature (Min-Max) (°C) -40 to 105
    • Analog Comparator 2
    • Cache (kB) 0
    • Debug Features JTAG, Serial Wire Debug, cJTAG
    • EEPROM (kB) 4
    • External Bus Interface n/a
    • FlexMemory (KB) 64
    • I/O Pins 29
    • Independent ADC modules 1
    • Internal Flash (kB) 256
    • Internal RAM (kB) 32
    • Max Simultaneous ADC channels 1 DP14 SE
    • Pulse Width Modulators - Channels 10
    • Sample Exception Availability Y
    • Serial Interface - Number of Interfaces 4
    • Serial Interface - Type UART, SPI, I2C, I2S
    • Supply Voltage (Min-Max) (V) 1.71 to 3.6
    • Timer type Low Power Timer, Periodic Interrupt Timer, Programmable Delay Block
    • Total DMA Channels 16
    • Total Flash memory (kB) 320
    • LQFP-48

The MK20DX128VLF5 can also be used, but the memory footprint (Flash and RAM) has to be reduced. The MKL27Z256VFT4 would be an excellent alternative (build-in bootloader, 8 mA run mode current with peripherals, 4 mA wait mode current), but the case is QFN48 and therefore you have to change the PCB layout.

-- Peter Schmid - 2016-03-30


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Topic revision: r13 - 2016-11-12 - PeterSchmid
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