https://github.com/codingabi/cambridgesoundworksdigitalirremote

Digispark/ATtiny85 DIY based remote control for a vintage Cambridge SoundWorks Digital CSW250 speaker system
https://github.com/codingabi/cambridgesoundworksdigitalirremote

arduino attiny85 csw250 digispark infrared optocoupler x9c103

Last synced: 3 months ago
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Digispark/ATtiny85 DIY based remote control for a vintage Cambridge SoundWorks Digital CSW250 speaker system

• Host: GitHub
• URL: https://github.com/codingabi/cambridgesoundworksdigitalirremote
• Owner: codingABI
• License: cc0-1.0
• Created: 2025-02-07T16:24:47.000Z (3 months ago)
• Default Branch: main
• Last Pushed: 2025-02-25T22:30:38.000Z (3 months ago)
• Last Synced: 2025-02-25T23:29:44.605Z (3 months ago)
• Topics: arduino, attiny85, csw250, digispark, infrared, optocoupler, x9c103
• Language: C++
• Homepage:
• Size: 1.1 MB
• Stars: 0
• Watchers: 0
• Forks: 0
• Open Issues: 0
• Metadata Files:
  • Readme: README.md
  • License: LICENSE

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README

        
# CambridgeSoundWorksDigitalIRRemote

A Digispark/ATtiny85 DIY based IR (infra-red) remote control for a vintage Cambridge SoundWorks Digital CSW250 2.1 speaker system from 1999. This speaker system is connected to my TV and is responsible for the TV-audio.

![Perfboard of the CambridgeSoundWorksDigitalIRRemote](assets/images/CambridgeSoundWorksDigitalIRRemote.jpg)

The *CambridgeSoundWorksDigitalIRRemote* replaces the original speaker system "remote" control, which has some disadvantages:

- Cable bounded (Max. 2 meters distance)

- Without turning off the speaker system, the speaker system has an idle power consumption of about 7.5 W (even without audio input)[^1]

- With turning off the speaker system, the system has a power consumption of about 3.1 W[^2]

- To turn off the speaker system, the volume level has to be set to minimum volume level

- After turning on the speaker system the previous volume level has to restored manually

The *CambridgeSoundWorksDigitalIRRemote* allows me use the IR wireless controller from my TV to 

- turn on/off the speaker system 

- automatically restore the last used volume level after turning on

- change the volume level 

- mute/unmute

## License and copyright

My [code](CambridgeSoundWorksDigitalIRRemote/CambridgeSoundWorksDigitalIRRemote.ino) and this page is licensed under the terms of the CC0 [Copyright (c) 2025 codingABI](LICENSE). 

### Used external board and libraries from Arduino IDE Board and Library Manager:

- Board: ATTinyCore 1.5.2, LGPL version 2.1 by SpenceKonde 

- Libraries: 

  - IRremote (4.4.1, MIT license)

    - Initially coded 2009 Ken Shirriff http://www.righto.com

    - Copyright (c) 2016-2017 Rafi Khan https://rafikhan.io

    - Copyright (c) 2020-2024 Armin Joachimsmeyer

## Hardware

- Digispark ATtiny85 Microcontroller with reset pin [configured](#pin-5-of-digispark-as-io-pin) as I/O pin

- Digital potentiometer X9C103

- IR-Receiver VS1838B

- Optocoupler 817A

- Cambridge SoundWorks Digital CSW250

- Sony KDL-40W4500 TV with Sony RM-ED011 remote controller

> [!WARNING]

> The *CambridgeSoundWorksDigitalIRRemote* was designed only for my combination: Cambridge SoundWorks Digital CSW250 and Sony KDL-40W4500/Sony RM-ED011. Other TVs/IR-Remote controls could also work, if you find the appropriate IR signals and adjust my [code](CambridgeSoundWorksDigitalIRRemote/CambridgeSoundWorksDigitalIRRemote.ino)

## Used development environment

Arduino IDE 1.8.19 (Without "real portable" support version 2.* makes no sense for me https://forum.arduino.cc/t/arduino-ide-2-0-portable/, https://github.com/arduino/arduino-ide/issues/122 ...)

IDE-Board settings:

- ATtiny85 (Micronucleus / Digispark)

- Clock: "8 MHz (no USB)" (8 MHz reduces the [power consumption](#power-consumption)) 

## Appendix

### Schematic

![Schematic](assets/images/Schematic.png)

> [!NOTE]

> The schematic shows a female Mini-DIN-6 connector

### Cambridge SoundWorks Digital CSW250

![Cambridge SoundWorks Digital CSW250](assets/images/CSW250.png)

#### Original remote control

The original remote control is cable bounded and connected by a Mini-DIN-6-Connector to the speaker system. 

![PCB CT5210B frontside](assets/images/PCB_CT5210B_frontside.png)

![PCB CT5210B backside](assets/images/PCB_CT5210B_backside.png)

After analyzing the PCB I got the following schematic:

![PCB CT5210B schematic](assets/images/PCB_CT5210B_Schematic.png)

> [!NOTE]

> The schematic shows a female Mini-DIN-6 connector

| SW1A | Reaction at the speaker system |

| --- | --- |

| Open | Turned off |

| Closed | Turned on (~1.3 mA between Mini-DIN-6 pin 6 and 3) |

The *CambridgeSoundWorksDigitalIRRemote* replaces the mechanical switch SW1A with an optocoupler. 

| Mini-DIN-6 pin | Color | Connected to speaker system (my assumption) |

| --- | --- | --- |

| 1 | Red | Ground |

| 2 | White | 5.6 V (seems to be regulated) |

| 3 | Green | Turns on/off the audio amplifier (Pin 6 and 3 connected=On, Pin 6 and 3 disconnected=Off) |

| 4 | Yellow | Audio volume level (0.76 V = Minimum volume, 5.14V = Maximum volume)  |

| 5 | Blue | Not connected |

| 6 | Black | Vcc (15-18 V, when Pin 6 and 3 are not connected. Decreases to ~85%, when Pin 6 and 3 are connected) |

The original remote control uses a linear B50K potentiometer RV1. Resistor R201 changes the linear to a non linear behaviour (see the following red line).

![Voltage on Mini-DIN-6 pin 4 on the original remote control and CambridgeSoundWorksDigitalIRRemote](assets/images/VoltageMiniDin6Pin4.svg)

The *CambridgeSoundWorksDigitalIRRemote* uses a digital, 100-steps, linear potentiometer with 10K (because I had no 50K). To get a similar non linear behaviour (Green line) and to ensures that my digital potentiometer did not get more then the allowed 5 V, I had to lower the resistors:

- R200 to 1K

- R201 to 5K1

- R202 to 2K

### Sony RM-ED011

My Sony TV KDL-40W4500 has a "RM-ED011" IR remote control and the *CambridgeSoundWorksDigitalIRRemote* uses it to control the Cambridge SoundWorks Digital speaker system.

![Sony RM-ED011 Remote control](assets/images/SonyRM-ED011.png)

The IRremote example [ReceiveDump](https://github.com/Arduino-IRremote/Arduino-IRremote/blob/master/examples/ReceiveDump/ReceiveDump.ino) shows me the following addresses and commands and I use some of them for the *CambridgeSoundWorksDigitalIRRemote*:

| Button | Address/Device Code | Command |

| :---: | :---: | :---: |

| ![Button 01](assets/images/bnt01.png) | 0x01 | 0x3A |

| ![Button 02](assets/images/bnt02.png) | 0xA4 | 0x3D |

| ![Button 03](assets/images/bnt03.png)* | 0x01 | 0x15 |

| ![Button 04](assets/images/bnt04.png) | 0x97 | 0x1B |

| ![Button 05](assets/images/bnt05.png) | 0x97 | 0x1A |

| ![Button 06](assets/images/bnt06.png) | 0x97 | 0x19 |

| ![Button 07](assets/images/bnt07.png) | 0x97 | 0x1C |

| ![Button 08](assets/images/bnt08.png) | 0x1A | 0x58 |

| ![Button 09](assets/images/bnt09.png) | 0x97 | 0x18 |

| ![Button 10](assets/images/bnt10.png) | 0x77 | 0x60 |

| ![Button 11](assets/images/bnt11.png)* | 0x77 | 0x52 |

| ![Button 12](assets/images/bnt12.png)* | 0x01 | 0x38 |

| ![Button 13](assets/images/bnt13.png) | 0x97 | 0x28 |

| ![Button 14](assets/images/bnt14.png) | 0x01 | 0x17 |

| ![Button 15](assets/images/bnt15.png) | 0xA4 | 0x5B |

| ![Button 16](assets/images/bnt16.png) | 0x01 | 0x25 |

| ![Button 17](assets/images/bnt17.png) | 0x01 | 0x65 |

| ![Button 18](assets/images/bnt18.png) | 0x01 | 0x74 |

| ![Button 19](assets/images/bnt19.png) | 0x01 | 0x75 |

| ![Button 20](assets/images/bnt20.png) | 0x01 | 0x34 |

| ![Button 21](assets/images/bnt21.png) | 0x01 | 0x33 |

| ![Button 22](assets/images/bnt22.png) | 0x97 | 0x23 |

| ![Button 23](assets/images/bnt23.png) | 0x97 | 0x36 |

| ![Button 24](assets/images/bnt24.png) | 0x01 | 0x60 |

| ![Button 25](assets/images/bnt25.png) | 0x03 | 0x4C |

| ![Button 26](assets/images/bnt26.png) | 0x03 | 0x4D |

| ![Button 27](assets/images/bnt27.png) | 0x03 | 0x4E |

| ![Button 28](assets/images/bnt28.png) | 0x03 | 0x4F |

| ![Button 29](assets/images/bnt29.png)* | 0x01 | 0x00 |

| ![Button 30](assets/images/bnt30.png)* | 0x01 | 0x01 |

| ![Button 31](assets/images/bnt31.png)* | 0x01 | 0x02 |

| ![Button 32](assets/images/bnt32.png)* | 0x01 | 0x03 |

| ![Button 33](assets/images/bnt33.png)* | 0x01 | 0x04 |

| ![Button 34](assets/images/bnt34.png)* | 0x01 | 0x05 |

| ![Button 35](assets/images/bnt35.png)* | 0x01 | 0x06 |

| ![Button 36](assets/images/bnt36.png)* | 0x01 | 0x07 |

| ![Button 37](assets/images/bnt37.png)* | 0x01 | 0x08 |

| ![Button 38](assets/images/bnt38.png) | 0x01 | 0x3F |

| ![Button 39](assets/images/bnt39.png)* | 0x01 | 0x09 |

| ![Button 40](assets/images/bnt40.png) | 0x77 | 0x76 |

| ![Button 41](assets/images/bnt41.png)* | 0x01 | 0x12 |

| ![Button 42](assets/images/bnt42.png)* | 0x01 | 0x13 |

| ![Button 43](assets/images/bnt43.png)* | 0x01 | 0x10 |

| ![Button 44](assets/images/bnt44.png)* | 0x01 | 0x11 |

| ![Button 45](assets/images/bnt45.png)* | 0x01 | 0x14 |

| ![Button 46](assets/images/bnt46.png) | 0x01 | 0x3B |

*TV can be turned on with this button

### Power consumption

The *CambridgeSoundWorksDigitalIRRemote* gets its 5 V supply voltage from the USB port of my Sony-TV. When the Sony-TV is turned off about ~22 minutes later the USB port will be automatically disconnected. 

Before disconnecting the 5 V supply voltage, the power consumption of the *CambridgeSoundWorksDigitalIRRemote* is dependent on the used voltage on the Digispark "5V"-pin, the clock speed and sleep mode:

| "5V"-pin voltage | Clock speed | Sleep mode | Power consumption | Comment |

| --- | --- | ---- | --- | --- |

| 5.0 V | 16.5 MHz, tuned of USB (USB) | none | 116 mW | 5 V from TV connected to "5V"-Pin of the Digispark |

| 5.0 V | 16.5 MHz, tuned of USB (USB) | SLEEP_MODE_IDLE | 93 mW | 5 V from TV connected to "5V"-Pin of the Digispark |

| 5.0 V | 8 MHz (no USB) | none | 96 mW | 5 V from TV connected to "5V"-Pin of the Digispark |

| 5.0 V | 8 MHz (no USB) | SLEEP_MODE_IDLE | 80 mW | 5 V from TV connected to "5V"-Pin of the Digispark |

| 4.7 V | 8 MHz (no USB) | SLEEP_MODE_IDLE | 70 mW | 5 V from TV connected to Digispark USB port (My Digispark uses a S4 Schottky diode with a forward voltage of ~0.3 V)[^3] |

| 4.3 V | 8 MHz (no USB) | SLEEP_MODE_IDLE | 65 mW | 5 V from TV connected via a 1N4007 diode to "5V"-Pin of the Digispark[^4] |

Below 8 MHz the ATtiny85 can not receive IR signals from my Sony RM-ED011 (At least with the used library IRremote). 

As as result of this table the *CambridgeSoundWorksDigitalIRRemote* uses 4.3 V, "8 MHz (no USB)" and SLEEP_MODE_IDLE 

=> **65 mW** power consumption[^5]. 

### Pin 5 of Digispark as I/O pin

My Digispark clone uses pin 5 as a reset pin. To use this pin as an I/O pin I had to change a fuse:

```

hardware\tools\avr\bin\avrdude.exe -P com4 -C hardware\tools\avr\etc\avrdude.conf -b 19200 -c avrisp -p attiny85 -n

hardware\tools\avr\bin\avrdude.exe -P com4 -C hardware\tools\avr\etc\avrdude.conf -b 19200 -c avrisp -p attiny85 -U hfuse:w:0x5F:m 

```

> [!WARNING]

> After that the Digispark can only be programmed by a USB-micronucleus-bootloader or a high voltage programmer!

Pin 5 is a "weak" pin and can not provide as much power as the other I/O pins, but can provide the needed ~1.5 mA to drive the used optocoupler.

[^1]:Replacing the original power supply TEAD-66-153000V with a smaller/newer 15 V power supply (for example https://www.amazon.de/dp/B0D2K7L311?ref=ppx_yo2ov_dt_b_fed_asin_title) reduces the idle power consumption to 3.8 W

[^2]:Replacing the original power supply TEAD-66-153000V with a smaller/newer 15 V power supply (for example https://www.amazon.de/dp/B0D2K7L311?ref=ppx_yo2ov_dt_b_fed_asin_title) reduces turned off consumption to ~0 W

[^3]:"Pin high" voltage for pin 5=2.4 V, optocoupler If=1.6 mA, Ic=1.3 mA, Uceo=0.2 V 

[^4]:"Pin high" voltage for Pin 5=2.2 V, optocoupler If=1.4 mA, Ic=1.1 mA, Uceo=1.8 V (not optimal, but working)

[^5]:Most of the power is not consumed by the ATtiny85. About 75% is consumed by the other used electronic components (Builtin LED, driving the optocoupler, digital potentiometer, USB data lines,...)