IR Transreceiver

Contents of Readme

1. About
2. About IR
3. Modules
4. Interface Description
5. Simulation
6. Test
7. Status Information
8. Issues
9. Licence

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About

This repository contains modules related to infrared (IR) emitters and receivers, such as remote controls. All modules in this repository requires external IR devices. These modules are communicated via single pin which kept high when not used. (Pull-up)

About (Implemented) IR

IR or Consumer IR (CIR) is a widely used Optical wireless communication (OWC) method. IR transmisson employ Infrared light to transmit data. They require line of sight to operate. They usually use 38 kHz as carrier frequency. Data is usually modulated with Amplitude-shift keying (ASK). Source: Wikipedia

Implemented modules decode/encode 0 as a short low (~600µs, no max.) followed by a short high (~600µs, max. 990µs), and 1 as a short low (~600µs, no max.) followed by a long high (~1.6ms, between 1-1.99ms). Any high period longer than 2ms ends transmisson. Transmission begins when an arbitrary low followed by an arbitrary high received. Transmitting no data or data smaller then 8 bits interpreted as repeat press.

Modules

ir_decoder module

General Description:

Module ir_decoder decodes the received IR signal. Width of the decoded code controlled by parameter CODEBITS. If received code is longer than CODEBITS, only least significant bits are kept. Module requires two clock. Clock clk_100kHz must be around 100kHz, in testing 97.656KHz is used. System clock, clk, can be any multiple of clk_100kHz.

Working Principle:

After a reset ir_decoder checks for the start condition, which is an arbitrary low followed by an arbitrary high. After receiving start condition, ir_decoder starts to decode. Decoded bit value determined by counting the duration of the rx high pulses and stored at the negative edge of rx. Durations less than 990µs interpreted as 0, durations between 1ms to 1.99ms interpreted as 1. If the duration is longer then 2ms end condition is generated and no data is decoded. Exact durations depends on the period of clk_100kHz, given values assume period of 10µs. If length of the received data is shorter than 8 bits or no data is received, repeat press signal, repeat_press, is generated and code is not updated. When a new code is decoded, newCode pulse with a length of a one clk is generated.

RGBremoteController module

General Description:

RGBremoteController can be used to control a RGB LED with a remote controller. Implemented remote has following buttons:

• 2 Brightness button
• On button, Off button
• Red, Green, Blue and White buttons
• 4x3 custom color buttons
• 3 diffrent mode buttons (Flash, Strobe and Smooth)
• Mode switching button

RGBremoteController requires ir_decoder module to operate and includes following submodules:

Submodule	Purpose
RGBremoteMapper	Decodes button number from code
rgb_led_controller8	PWM RGB pins to control color
brightnessControllerRGB	Modulate PWMed RGB pins to adjust brightness
pulseGen	Generate pulses to change color in Flash and Strobe mode (~3,3Hz)

Smooth mode is not implemented. Repeated presses are not recognized. Colors can be edited with local parameters; WHITE, REDx, GREENx and BLUEx.

RGBremoteMapper module:

RGBremoteMapper maps codes to button numbers. Mapping can be changed with local parameters btn_y_x, where x and y are coordinates with btn_0_0 is the top left button. Unknown codes mapped as button number 31.

Interface Description

ir_decoder Interface

Port	Type	Width	Description
clk	I	1	System Clock
clk_100kHz	I	1	100kHz Clock, used in decoding
rst	I	1	System Reset
rx	I	1	Receiver Pin
code	O	CODEBITS	Decoded code
repeat_press	O	1	Indicates repeat press received
newCode	O	1	Indicates a new code decoded

I: Input O: Output

• System Clock, clk, frequency can be any multiple of clk_100kHz. 100 MHz is used it testing.
• If received code is shorter than CODEBITS, MSBs will be 0.
• If received code is longer than CODEBITS, LSBs are kept.
• clk_100kHz should be approximately 100kHz, some variation does not affect functionality. During simulation and testing 97.656kHz clock is used.

RGBremoteController Interface

Port	Type	Width	Description
clk	I	1	System Clock
rst	I	1	System Reset
code	I	32	Decoded code
newCode	I	1	Indicates a new code decoded
red_o	O	1	Red LED pin
green_o	O	1	Green LED pin
blue_o	O	1	Blue LED pin
an	I	1	LEDs are connected in anode mode

I: Input O: Output

RGBremoteMapper:

Port	Type	Width	Description
code	I	32	Decoded code
valid	O	1	Indicates the code is valid
button	O	5	Button Number, 31 if unvalid

I: Input O: Output

Simulation

ir_decoder Simulation

Module ir_decoder simulated with sim_ir_dec.v. Module simulated with default CODEBITS value, 32 bits. One 16bit code (0x0FAA) is send via rx. Clock signal clk_100kHz is generated with onboard module clkGen97k656hz.

Test

ir_decoder Test

Module ir_decoder tested with ir_decoder_test.v and Basys3_0.xdc. Module tested with default CODEBITS value, 32 bits. Receiver Pin connected to JB10 port. Decoded code send via UART and shown on seven segment display (SSD). Left most switch, SW15, used to choose which portion of the code is shown. When SW15 is high MSBs, when low LSBs are shown. Dots on the SSD indicates repeat press. UART transmit connected to JB2 port and USB-RS232 transmit port. Baudrate set to 460.8k. 8 bit data, no parity and 1 bit stop is used. These values are hardcoded in ir_decoder_test.v and can be changed from there. (For more information check UART repository) When a new code decoded, it is transmitted automatically via UART in four transmissons, MSB first.

Module irdec_test can also be used as IR remote decoder to extract 32 bit codes from IR remotes, and see them.

RGBremoteController Test

Module RGBremoteController tested with rgbRemoteTest.v and Arty-A7-100_0.xdc. LD0 controlled with the remote. All of the buttons are tested.

Status Information

Last Simulation:

• ir_decoder: 18 January 2021, with Vivado Simulator

Last Test:

• ir_decoder: 18 January 2021, on Digilent Basys 3
• RGBremoteController: 20 January 2021, on Digilent Arty A7

Issues

ir_decoder:

• Rarely module stucks and needs reset to work again, happens when buttons pressed rapidly.

License

CERN Open Hardware Licence Version 2 - Weakly Reciprocal