The MusicReactor is a demo application for I²C LED driver (PCA9955B)
and I²C stepper motor controller (PCA9629A) using MicroPython.
The MIMXRT1010-EVK is chosen as MocroPython running platform
A brief demo video is avairable on YouTube.
As shown in the video, the LEDs and the stepper motors act flashing and switching rotation synchronized to the music beat.
The demo is configured as next picture.
Demo system diagram
Boards in the video
A music signal is fed from source (PC or smart phone) via 3.5mm plug.
The signal goes into an "interface board" which is made as an Arduino shield board.
The interface board has two 3.5mm jack those are connected in parallel. Either one of them can be input and other can be output for amplifier integrated speaker.
The interface board converts the music signal to envelope waveform for ease of handling amplitude information in MCU. The waveform is fed into "A0" pin of MCU board.
MIMXRT1010-EVK is chosen for this demo but any MicroPython enabled MCU can be used. I chose RT1010 MCU since its lightest MicroPython supported MCU from NXP.
IMXRT1010-EVK detects peak of "A0" pin input. It samples the "A0" analog input in every 10ms (100Hz). The sampled data is compared with previous sample if it has certain defference.
If the level is avobe threshold (the threshold is adaptive), the MCU detects it as peak then LED flashing and switching motor direction are done through I²C interface.
The LED driver is main device of this demo. It flashes LEDs synchronized to music beat.
The Stepper motor controllers are option. If no stepper motor controller presented in the demo, the demo program just ignores its absence.
16 channel LED driver: PCA9955B is used. The access of the LED driver from MCU is done with target address of 0xEC (0x76 in 7 bit presentation).
This address is called as "sub address 1" in PCA9955B and enabled in default state after reset.
All LED access are done with this address. So the multiple PCA9955B can be connected to this demo to perform same regardless to those I²C target address settings.
This demo is intended to use demonstration boards of OM13483. Color(RGB) LED and white LED assignment is made for this OM13483.
If user want to use PCA9955B-ARD, LED assignment may need to be changed and set EN pin input on the board.
The demo program operates "Gradation Control" function on PCA9955B. All LED outputs are controlled with this function. The color LEDs are controlled automatically inside of the LED driver. Each red, green and blue channels are controlled by same waveform continuously but different phases. It makes color gradations. White LED is also controlled with the gradation control but it triggered by audio peak in single-shot.
To enhance light effect, all channel brightness are controlled by PWM on addition to the gradation control.
(The gradation control controls the brightness in output current control. User can add brightness modulation by PWM control.)
Stepper motor is just an option in this demo.
If the stepper motor controller is not connected, the demo just ignores its absence.
PCA9629A is the stepper motor controller and its "Five PCA9629 Stepper Motors Controller Board" is used.
There are 5 motors but all motor controllers are controlled by same target address:0xE0 (0x70 in 7 bit presentation).
The 0xE0 is the ALLCALL address in PCA9629A.
Using this address, all stepper motor controllers in same way regardless to the setting of I²C target address setting.
The 0xE0 is the ALLCALL address in PCA9955B too. To avoid the conflict, the ALLCALL adress in PCA9955B is masked.
Since all motor controller is operated with one target address, any number of controller can run on this demo.
No need to be 5 motors always.
After the system reset, the motors go home position to align direction of the arm on spindle.
Then the rotation is started.
The motor rotation direction switched by peak detection. All motor actions are synchronized by command from MCU.
This demo requires "MIMXRT1010-EVK", "OM13483" (or "PCA9955B-ARD").
The stepper motor controllers are option.
On addition to those, user need to prepare an interface board by him/her-self.
The interface board can be built either way: simple or flexible versions.
The simple circuit board can be made very easy. A few passive components and connectors.
It just forms connect 3.5mm audio jacks in parallel and simple diode detecotr circuit.
The detector converts the music signal on 3.5mm jack to audio amplitude waveform and fed into MCU AD-conveter input pin.
This circuit may be good for first try because it's very simple. However, this type is sensitive for input signal level. This demo is expecting to have consumer audio line level. If it is less than expected, the demo will not react to the music. User need to adjust output volume on music source device carefully.
Interface board: simple circuit version
Another option could be more analog processing on the interface board.
This sample is called "flexible interface" because this version can accept wider range of input signal level.
This circuit is having 100Hz LPF (for ease of detecting beat) and op-amp based rectifier with gain.
If the signal level is too big, a VR in input stage can be used for attenuation.
Interface board: flexible circuit version
Software setup need to be done in two steps. #1:Install MicroPython, #2:Install library and application code
Since the MicroPython is an interpreter, its executable need to be installed into the MCU first.
The executable binary file can be downloaded from download site.
The file can be downloaded from this link
The downloaded file need to be copied into the MCU.
Set the J1 jumper pin in middle position (shorting 5-6 pins) left most position (shorting 1-2 pins) and connect USB cable to J41. When the USB cable is connected to PC, it will appear as USB storage device named "RT1010-EVK".
Copy downloaded "MIMXRT1010_EVK-20230426-v1.20.0.bin" file into the "RT1010-EVK" by drag&drop. When the copy completed, the USB strage will be re-mounted (appear after disappear).
MIMXRT1010-EVK setting for Step 1: Install MicroPython
Copying MicroPython executable file into MCU by drag&drop
After MicroPython instration, change jumper configuration and USB connection. Set J1 jumber to short 3-4 pins and connect USB cable to J9.
On PC, use Thonny application to copy the Python code into the MCU.
For details of Thonny operation, please watch this video (turn-ON YouTube subtitle feature for English).
Everything in src directory in this repository should be copied into MCU's flash/ folder.
MIMXRT1010-EVK setting for Step 2:Install library and application code
Copying demo code and library into MCU by using Thonny
With completing these steps, the demo is ready!
The demo will be running after reset or power-cycling of the system :)
This demo is just detecting music signal amplitude. Some very old music or recent music which is heavily amplitude complessed may not give good result. It will be good idea to monitor the waveform from music source or MCU "A0" input pin which has amplitude information by oscilloscope when selecting demo source.
When using flexible circuit version interface board, music source output level may not need to adjust carefully.
Even the signal is clipped on the interface corcuit, the demo may work correctly. However, if you take signal from speaker output from power-amplifire, it may need to be adjusted.
The flexible version circuit has an LED to indicate "overload". Overload means the signal level is close to satulation. If this LED is continuously kept ON, the signal may need to be attenuated.
- This demo had been built with 'mikan' class libraries
- I²C LED driver (PCA9955B)
- I²C stepper motor controller (PCA9629A)
- MIMXRT1010-EVK
- MicroPython.