DMX CTRL

DMX_CTRL

A DMX512-combatible light control platfrom for medium-complex projects.

There are currently standard solutions for light control that fill specific needs:

• DMX512 compatible stage lighting ($13 - $ 300) usually with Full RGB control and maybe XYZ Control
• Custom solutions for complex installations using WS1812 Strips (Fadecandy and others). This for Example: http://www.deniznicoleart.com/
• Progammable light controllers that can play back preprogrammed patterns that can get triggered by DMX512 (Chinese closed source products)

What is missing is a controller that combines the simple, low cost wiring and control of DMX512 with the flexibility of a customizable firmware and control options.

Usage Case

The follwing is an outline of the current usage case for an art car and why a specific controller is needed. The art car has multiple light-elements that need central coordination/sequencing but also reacts to other stimulus:

• "Hoover Field" -> WS2812 Light Strips around the base that display a moving pattern syncronized with the speed of the car.
• "Engines" -> Simple RGB Strips that are playing a preprpogrammed startup/shutdown seuqence and a animation while moving
• "Internal Lights" -> Lantern with red LED's that are supposed to flicker and occasionally fail
• "Mood Lighting" -> White LED Strips that can be controlled in brightness
• "Centralized Control Panel" -> Touchscreen control to trigger and sequence effects (Either Cheap Windows Tablet or Raspberry Pi)

These are all usage cases that are not "Simple" DMX RGB-Light cases but also do not warrant complex solutions like FadeCandy that need a lot of programming, USB wiring and complex control computers. While these effects could be achived with a handful of Arduinos it makes central control more compleicated as there is no common control bus easily available and the processing power of Arduinos is limited.

Feature List

• Can act as DMX Master or Slave
• Up to 2 WS8212 LED strips with up to 512 Pixel
• 2x RGB LED/Strip and 1xRGBW LED/Strip support with up to 3A/12V per LED (Or optionally drive PWM controlled servos)
• Configurable via USB/Serial Terminal
• Up to 2 Analog Inputs (Can be used to control effects or act as Triggers)
• 8 Address Lines (Optional LCD via i2C and Encoder via GPIOs instead)
• 2 Mode Jumpers to hard-select options (Simple Mode (PWM Only) / Extended Mode (PWM+Strips+FX) and USB Enable/Disable)
• Button to restore settings on startup or Test Mode
• External UART or option to connect ESP8266 WiFi Board
• USB to use as a Computer -> Master Bridge
• Total Cost per Board ~$16 (Most of that (8$) are MOSFETs so it depends on how many LED channels are needed)
• Board size 10x5 cm

Current Status

• DMX512 Control of PWM Channels -> Working
• DMX Address setting via Jumpers -> Working
• Serial Shell to control/Save settings -> Working
• Load defaults on startup -> Working
• Clear settings (Hold button on power-up) -> Working
• Test Mode (Press button after power up, cycles through all LED channels) -> Working
• Triggers -> Working
• Plugin Manager -> Working
• Example Plugins -> Working
• WS2812 Support -> Working
• Serial Control (Wifi/Serial/USB) -> Working
• Serial DMX Protocol -> Working

BOM Cost

The BOM cost for the simplest implementation is

• $2.00 for the board
• $2.00 for the Bluepill STM32F103 Board
• $0.70 for the RS485 Module
• $4.00 for Misc (Resistors, pin headers, switch)
• $0.80 per Mosfet for controllable Channels So somewhere between $9 to $17.

Development Enironment

The software is developed with ST Microelectronics STM32CubeIDE 1.3.0 The software framework was generated with STM's ST CubeMX Solution (Config file included in DOC folder) and uses ST's HAL framework. (Not my favorite but that's what they want you to use...) I use a ST-Link V2.0 Clone to upload/Debug software. (Eventually there might be a USB DFU Firmware Upload Client....)

You can also use MS Visual Studio Code + PlatformIO. This is prefered if you run into issues with fake STM32's as PlatformIO uses openOCD which can set the device ID directly and program these devices. There are currently a lot of bluepill STM32F103 board clones with fake STM32F103 circulating on Amazon. (I ended up with about 20...Aarrggghhh...) As a workaround, you can edit the file ~/.platformio/packages/tool-openocd/scripts/target/stm32f1x.cfg and change the line: set _CPUTAPID 0x1ba01477 to: set _CPUTAPID 0x2ba01477

USB does not seem to work on my clones but I need to further test that....(I had issues like that before and usually it had to do with crappy USB cables...)

Here is another description how to fix it in STM32CubeIDE for openOCD debugging: https://community.st.com/s/question/0D50X0000BTd7Zi/how-to-deal-wirh-could-not-verify-st-device-

Update: Not all fake chips have 128 kB, some only have 64 kB. At that point the FW can not write the configruation to page 127... This will cause a Hardware Fault. Change the EEPROM page in eeprom.h from 127 to 63 and modifiy the .id file to reflect the smaller FLASH size. (Less effects will obviously fit in there....) I should probably figure out a way to detect flashsize automatically.....

Serial Shell

List of Serial Shell Commands

FX Plugin API

FX Plugin Manual

Notes

DMX Registers

Depending on mode selection the module will present itself with either 11 or 26 DMX Registers. In Mode 1 only the first 11 registers are available and provide simple PwM control.

In Mode 2 additional 15 registers are present for FX control. (WS2812B supporty will only be present in that mode...) Except for the FX_SELECT register these don't do anything by default but have to be used in plugins. and functionality will vary.

Jumper Options

ADDRESS

The 8 Address Jumpers set the DMX Start address for the Registers. As there are 512 possible DMX Addresses the Address set via jumpers will be multiplied by 2.

MODE

Jumper 1 Disabled = DMX Register Mode 1 (Only PWM Control, not FX) Enabled = DMX Register Mode 2 (PWM + WS2812B Strips, FX enabled

In DMX Mode 1 only the following Registers will be available: #define MAX_BRIGHTNESS 0 #define CH1_RED 1 #define CH1_GREEN 2 #define CH1_BLUE 3 #define CH2_RED 4 #define CH2_GREEN 5 #define CH2_BLUE 6 #define CH3_RED 7 #define CH3_GREEN 8 #define CH3_BLUE 9 #define CH3_WHITE 10

In DMX Mode 2 additionally the following Registers will be available: #define FX_SELECT 11 #define STRIP1_PATTERN 12 #define STRIP1_SPEED 13 #define STRIP1_SIZE 14 #define STRIP1_COMPLEXITY 15 #define STRIP1_V1 16 #define STRIP1_V2 17 #define STRIP1_V3 18 #define STRIP2_PATTERN 19 #define STRIP2_SPEED 20 #define STRIP2_SIZE 21 #define STRIP2_COMPLEXITY 22 #define STRIP2_V1 23 #define STRIP2_V2 24 #define STRIP2_V3 25

Jumper 2 Disabled = No USB Support (Saves a lot of memory) Enabled = Enables Serial Port via USB

DMX Control Wires (A/B)

With my controller the follwing pinout works (Looking at a male connector): Pin 1 = GND Pin 2 = A Pin 3 = B Some controllers allow to swap A/B with a switch so your milage might vary....

DMX Termination

DMX needs to be terminated at the end of the chain with a 160 Ohm Resistor.

Power Supply

Board has been tested with 9 PWM channels with 216 RGB LED's with a total power consumption of 3.8A @ 12V. If only 12V is supplied make sure to add J5 so the microcontroller is powered.

Restoring Defaults

Pressing the button while powering up will erease all settings and restore the defaults.

Test Mode

Pressing the button after powering up will turn on test mode where the module cycles through all lights to test wiring

Triggers

The two trigger inputs can be set up in different ways:

Direct Control

The analog value (0...3.3V) is directly mapped onto one of the control registers. (For example an external inpout can be linked to the brightness of a channel or set the input parameter for an effect)

Threshold

A Specific value can be written to a specific control register wen crossing a threshold from low to high or from high to low. (For example a specific effect can be turned on/off via a switch)

USB Port

USB Support can be complelty commented out in main.h as it saves a lot of RAM/Flash. If USB Support is compiled in Mode Jumper 1 controls if it is eanbled or not. USB has been confirmed working both witrh original STM32103F and STM clones but it is imperative to use good USB cables. Also be aware that some boards will need R10 on the bluepill boards swapped from 10kOhm to 1.5kOhm. Both the Shell or the Serial DMX protocol can be run via USB. On Win10 no special driver is needed, the device will be recognizied as a Serial port. The serial port emulation via USB is not speed-controlled so in theory data can be written at full 12Mbit/sec Full USB speed....

Wifi/USB/Serial DMX Control

[TBD, Protocol Implemented, need sample App..] [TBD, need ESP2866 Sample Code and Sample App]

Master Control

TBD

WS2812B

The LED strips seem to be very sensitive regarding the voltage on the data line. R11/R12 in theory protect the first LED from dying on transient overcurrent on startup but some LED strips won't work. In that case just bridge R11/R12....

What's that strange connector footprint for the WS2812 connection?

The idea is to solder on wires and then use a zip-tie through the holes and hot-glue to secure the wires. Past projects had big problems with wires breaking off or shortening out... Maybe this will work.....

Acknowledgements

Example Code to use WS2812B on STM32 with DMA https://michaeltien8901.github.io/stm32/2018/07/19/Using-STM32-SPI-For-LED-STRIP.html

DMX512 Example https://github.com/carl3721/stm32-dmx512

References

• DMX Pinout https://interactive-online.com/resources/faq/dmx-512-connector-pinouts

• Fadecandy Webpage https://github.com/scanlime/fadecandy

• Ultra-Cheap DMX Lights (Just search for DMX512 RGB LED on ebay...)

Part References

Bluepill Boards https://stm32-base.org/boards/STM32F103C8T6-Blue-Pill.html

RS422 Converter https://alexnld.com/product/2pcs-5v-max485-ttl-to-rs485-converter-module-board-for-arduino/?utm_source=bing&utm_medium=cpc&utm_campaign=Product%20Ads(BSC)&utm_term=4578022847022738&utm_content=Ad%20group%20%231

(These can obviouslty be sourced way cheaper on ebay/alibaba/banggood... These links are just for reference...)

Board Design

• Board designed with KiKad
• For various (Legacy) reasons it will need the KiCad 4.0 Symbol/Footprint Library installed...
• Board size is 100mm x 50mm. In theory these could be paneled for JCLPCB.com but there is no cost advantage if you include V-Grooves. You could just produce PCB's with two boards next to each other and cut them yourself but I haven't tried that....

Known Issues (REV 1.0)

Schematic:

• RX/TX Swapped on Serial Connector (TBD if they are right or wrong on ESP-01 connector...)
• GND not connected on RS485 Module
• Add Button for ESP8266 Button to trigger events on startup

Layout:

• Make RS485 module base 2.54 mm longer (Or not.. apprently they come in two sizes.. Maybe add both sizes by adding another line of holes)
• Add silkscreen for Pin 1 to connectors
• Move RS232 Connector so it can be used in parallel with ESP-01 for Debug (Move further in so angled connector can be used....)
• Bluepill collides with mounting hole in corner
• Remove solder mask from high-current paths for tinning
• Battery collides with power connector
• Move labels for power supply to other side of connector or back
• Make holes for TO220 Larger so they fit flush
• RS485 module is rotated 180 Deg
• Create more room for programming connector on bluepill board by moving 5V Regulator
• Move Compyright Notice on Bottom to allow for Tinning
• For WS2812B Cable Connector, less extrame angle, 0.6mm smaller holes, Shink total size

Known Issues (REV 2.0)

Schematic:

Layout:

• Bluepill collides with mounting hole in corner
• Panelize Board
• Mounting holes for RS485 Transceiver should have been 2.54mm smaller, not bigger?
• Holes for TO220 should have been even bigger
• No coating on 5V rail to WS2812B

TODO

• Master Mode
• ESP-01 (ESP8266) Code/Example
• Serial DMX Protocol Example (In Processing....)
• RTC Support
• High Speed WS2812B USB Demo
• Overclocked Version

Ideas

WS2812B USB Mode

Run data as fast as possible via USB to 2 WS2812B strips. (512 LED * 30 us) + 60 us = 15.4 ms (64 FPS) 512 Leds = (512 * 3) * 1.2 bytes = 1843 Bytes

1843 Bytesa * 64 Frames = 117964 Bytes 117964 Bytes * 2 = 235929 Bytes = 1887436 Bits 12 MBits = 12000000 Bits 12000000 Bits / 1887436 = 6.35 So in theory we have 6.35x the bandwidth we need to update 2x 512 LED's 64 Times/sec....