EV1527 is a popular encoding format for ASK RF senders and receivers to transmit simple remote control messages.
Dedicated EV1527 Devices
In this section, you find dedicated EV1527 senders and receivers that already come with EV1527 encoding and decoding chips. They do not require any additional components or a microcontroller.
Once you add a microcontroller to your project, you can use any ASK sender and receiver to transmit EV1527-compliant code: the microcontroller then can act as EV1527 encoder and decoder, and produces the required 24-bit EV1527 codes.
EV1527 Requirements
Simple remote controls such as garage door openers and home automation plugs have very basic remote communication requirements:
- Unique Key Code: The digital code sent out by the remote control (sender) must be unique enough to not cause remote controls to interfere with each other and open or control the wrong devices.
- Simple On/Off Commands: The digital code also needs room for a limited data payload so that a remote control can control more than one device.
Implementation
One solution to these requirements was the EV1527 encoder chip that operates on the Low Range Device frequency bands, typically 315MHz (US) and 433MHz (Europe/Asia).
It uses the simple ASK modulation (a subtype of amplitude modulation) and encodes the control information as a 24-bit data package.
The first 20 bits are randomly set by the encoder manufacturer to uniquely identify a remote control. The remaining 4 bits control devices.
Since the sender can send out only fixed codes that are beyond the control of the user, the receivers typically have a pairing mode (aka learning mode) that allows them to pair themselves with the specific code emitted by a sender.
Pairing
During pairing, the receiver picks up the unique ID code sent out by the remote control.
Once paired, the receiver responds to control messages only if the first 20 bits match the ID of the initially paired remote control.
Sending Commands
Once you press a button on a remote control, it sends out a 24-bit data package:
The first 20bits are the unique remote control ID. The remaining 4bit are the payload. Each bit in this payload can represent a button on the remote control (up to 16 buttons).
Receiving Commands
Once the receiver picks up a control message with matching ID (the ID in the control message matches the ID that was stored during initial pairing), it looks at the 4bit payload.
Depending on how many channels the receiver supports, it responds to the appropriate bits in the control message.
For example, most typical EV1527-compliant receivers support four channels. When you press one of the first four buttons on a remote control, you can control one of the four data out pins of the receiver.
If that is the case, the receiver looks at the 4-byte payload and assigns the first four bits to its four digital outputs.
Limitations
Most EV1527-compliant receiver boards can only be paired to a remote control ID, but not to a specific remote control button.
So if you have a eight-button remote control, you cannot control two 4-channel receivers with it: each receiver pairs to the remote control ID and assigns the first 4 bit of the payload to its four channels.
Likewise, since receiver breakout boards can only be paired to one remote control ID, you cannot use multiple remote controls to control a receiver board.
…And Workarounds
All mentioned limitations are caused by the rigit way the embedded EV1527 encoders and decoders work. For simple remote control scenarios, this is absolutely fine because it makes using these devices extremely simple.
For more sophisticated scenarios (i.e. multiple remote controls for one device, assignment to specific buttons on a remote contol), all you need is to take control into your own hands:
- OOK instead of EV1527: use generic OOK (ASK) senders and/or receivers. This way, you are not limited anymore to hard-wired rules and behaviors
- Microcontroller: add a simple microcontroller to your project (such as ESP8266 or ESP32 C3), and use one of the EV1527 libraries to do the encoding and decoding yourself.
Depending on how you address things, you might use a microcontroller-based alternative either on the sender side or on the receiver side.
- Multiple Remote Controls (Sender): To use multiple remote controls with one receiver, all you really need is control over the sender ID. By using a microcontroller-based sender as remote control, you can clone one sender ID and use it with as many remote controls you want.
- Multiple Remote Controls (Receiver): A cheaper solution might be using a microcontroller-based setup on the receiver side, and continue to use default remote controls. All you need in this scenario is control over the pairing process: with a microcontroller-based approach, you can pair as many remote controls as you want and keep as many remote control IDs stored and approved as you like.
Hardware Requirements
Hardware requirements are minimal. When you get EV1527-compatible breakout boards, no external components are required.
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(content created Apr 16, 2024)