RISCV_IR USER GUIDE

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REVISION HISTORY

Revision No.	Description	Date
1.0	Initial release	04/18/2023
1.1	Update DEBUG&FAQ	04/08/2025

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1. OVERVIEW

Infrared Receiver (IR) is mainly used to analyze the signal sent by the infrared remote control, which is a series of binary pulse codes. In order to prevent the infrared signal from being interfered by other signals during wireless transmission, it is usually modulated at a specific carrier frequency (38KHZ) and then transmitted through the infrared transmitting diode. The IR receives the signal of the specific frequency after filtering out other clutter and restores it to a binary pulse code, that is, demodulation. The decoding methods supported by SigmaStar IR are Full, Raw, SW and RC, and the protocols supported are NEC, RC5 and RC6.

2. Keyword

None.

3. FUNCTION DESCRIPTION

3.1. Basic Function

• Support 5 groups of IR hardware.

• Pulse signals less than 170us will be filtered.

• The default clock frequency is 12MHZ, and the clock adjustment is not supported.

• Supported decoding modes are Full, Raw, SW and RC5 (note that RC6 software is not supported yet).

3.2. IR Decoding Method

SigmaStar's IR_IN signal can be decoded in four decoding modes: Full mode, Raw mode, SW mode, and RC mode.

When the IR_IN signal is in NEC/NEC-like format, Full/Raw/SW mode can be used for decoding.

When the IR_IN signal is in RC format, it can be decoded in RC/SW mode (currently the driver only supports RC5 format).

When the IR_IN signal is in other format, it can only be decoded in SW mode (it needs to be used with a decoder).

• Full mode

  The hardware can decode IR_IN signals in NEC/NEC-like format and identify user codes and key codes.

• Raw mode

  The hardware can decode IR_IN signals in NEC/NEC-like format, but cannot identify which part is the user code or key code, which needs to be determined by software.

• SW mode

  The hardware cannot identify any format from the IR_IN signal, and software is required to decode the signal format, user code and key code.

• RC mode

  The hardware can decode IR_IN signals in RC format and identify user codes and key codes.

As can be seen from the block diagram below, there are two main paths for infrared decoding. The upper path is Full/Raw/SW mode, and the lower path is RC mode.

Figure 2-1: IR Decode Block Diagram

3.3. Each Protocol Level Standard

NEC format:

• Logic0: 0.56ms high + 0.56ms low

• Logic1: 0.56ms high + 1.68ms low

• Header code: 9ms high pulse

• Off code: 4.5ms low pulse:

• Customer code: 8-bits customer code + 8-bits inverse or 16-bits customer code

• Command code: 8-bits command code + 8-bits inverse

• Total cycle time: 108ms

• Repeat key: 9ms Header code and 2.5ms Off code

  

  Figure 2-2: NEC Format Standard

NEC-like format:

• Logic0: short high + short low (usually 1:1)

• Logic1: short high + long low (usually 1:3)

• Header code: ultra long high width

• Off code: ultra long low width

RC5 format:

• Logic0: 888us high + 888us low (Manchester code)

• Logic1: 888us low + 888us high (Manchester code)

• Start bits: 2-bits logic1

• Toggle bit: Inverted every time when the key is released and pressed again

• Customer code: 5-bits customer code

• Command code: 6-bits command code

• Total cycle time: 114ms

• If a key is held over 114ms, it will repeat the signal every cycle time

  

  Figure 2-3: RC5 Format Standard

RC5-Extend format:

• Same as RC5 expect the second bit of SB is represented the 6^th bit of address code

  

  Figure 2-4: RC5-Extend Format Standard

RC6 mode 0 format:

• Logic0: 444us low + 444us high (Manchester code)

• Logic1: 444us high + 444us low (Manchester code)

  (Note the logic length is half of RC5 format and the level order is opposite)

• Header code: 2.666ms high pulse + 888us low pulse

• Start bit: 1-bit logic1

• Mode bits: 3-bit logic0 (in mode 0)

• Toggle bit: Inverted every time when the key is released and pressed again

• Customer code: 8-bits customer code

• Command code: 8-bits key code

• If a key is held over 114ms, it will repeat the signal every cycle time.

  

  Figure 2-5: RC6 Mode 0 Format Standard

4. HARDWARE CONNECTION INTRODUCTION

Connect the infrared receiver to the development board according to the direction indicated in the schematic.

Figure 4-1: IR Hardware Schematic

5. RISCV USAGE INTRODUCTION

5.1. Driver Path

sc/driver/sysdriver/ir/os/ir_os.h
sc/driver/sysdriver/ir/drv/pub/drv_ir.h
sc/driver/sysdriver/ir/drv/src/drv_ir.c
sc/driver/sysdriver/ir/drv/src/drv_ir_test.c
sc/driver/sysdriver/ir/hal/chipname/src/hal_ir.c
sc/driver/sysdriver/ir/hal/chipname/inc/hal_ir.h
sc/driver/sysdriver/ir/hal/chipname/inc/hal_ir_cfg.h

5.2. CONFIG Configuration

The config file is located at mak/options_chipname_riscv_isw.mak, enable CONFIG_IR_SUPPORT.

# Feature_Name = [DRV] IR driver support
# Description = IR driver support
# Option_Selection = TRUE, FALSE
CONFIG_IR_SUPPORT = TRUE

5.3. SYSDESC Configuration

The chipname_xxx.sys file is used to describe the hardware attributes of peripherals. The attribute values contained in the peripheral node can be used to configure the peripherals, similar to the Linux device tree. The file is located in sc/driver/sysdriver/sysdesc/hal/chipname/pub.

<ir0>
    [reg_u32_u16] 0x22CE200 0x200;
    [interrupts_u32_u32] INT_FIQ_IR_1 0xFFFF;
    [camclk_u32] CAMCLK_ir_nonpm0;
    [status_u8] 0;

Attribute	Description	Setting value	Remark
reg_u32_u16	Specify bank address	0x22CE200	Modification prohibited
interrupts_u32_u32	Specify interrupt number	INT_FIQ_IR_1	Modification prohibited
camclk_u32	Specify clock source	CAMCLK_ir_nonpm0	No modification required
status_u8	Select whether to enable the driver	1-enable; 0-disable	Can be modified as needed, the default is disable

5.4. PADMUX Configuration

Method 1: CONFIG_PADMUX_SUPPORT=TRUE

If the chipname_xxx.sys file is configured with the attribute <padmux>, then the PADMUX setting is directly configured here:

    <padmux>
        [schematic_u32_u32_u32] PAD_GPIOC_00 PINMUX_FOR_IR0_IN_MODE_1 MDRV_PUSE_IR,
                                PAD_GPIOC_01 PINMUX_FOR_IR1_IN_MODE_1 MDRV_PUSE_IR1,
                                PAD_GPIOC_02 PINMUX_FOR_IR2_IN_MODE_1 MDRV_PUSE_IR2,
                                PAD_GPIOC_03 PINMUX_FOR_IR3_IN_MODE_1 MDRV_PUSE_IR3,
                                PAD_PM_GPIO2 PINMUX_FOR_PM_IR_IN_MODE_1 MDRV_PUSE_IR4；
        [status_u8] 1;

Otherwise, by enabling the PADMUX driver, configure the pin multiplexing function in the chipname-xxx-padmux.c file, which is located in sc/driver/sysdriver/padmux/hal/chipname/src. You only need to add the following content to the corresponding schematic attribute:

    pad_info_t schematic[] =
    {
        {PAD_GPIOC_00 PINMUX_FOR_IR0_IN_MODE_1 MDRV_PUSE_IR},
        {PAD_GPIOC_01 PINMUX_FOR_IR1_IN_MODE_1 MDRV_PUSE_IR1},
        {PAD_GPIOC_02 PINMUX_FOR_IR2_IN_MODE_1 MDRV_PUSE_IR2},
        {PAD_GPIOC_03 PINMUX_FOR_IR3_IN_MODE_1 MDRV_PUSE_IR3},
        {PAD_PM_GPIO2 PINMUX_FOR_PM_IR_IN_MODE_1 MDRV_PUSE_IR4},
    };

The first column is the pin index number, which can be queried in sc/drivers/sysdriver/gpio/hal/chipname/pub/gpio.h;

The second column is the mode definition, which can be queried in sc/drivers/sysdriver/gpio/hal/chipname/pub/padmux.h;

The third column is the index name of the pin and matching mode, which can be queried in sc/drivers/sysdriver/padmux/drv/pub/drv_puse.h.

5.5. Sample Code

The demo source code is located at sc/driver/sysdriver/ir/drv/src/drv_ir_test.c.

/* The callback function, which will be called when receiving IR signal */
u32 ir_get_value(u32 group)
{
    u64 data;
    u8  repeat;
    u32 addr;
    u32 cmd_code;
    u32 key_value;

    data = drv_ir_key_dequeue(group); //Get the IR signal analysis result
    if (data)
    {
        repeat    = data & 0x1;       //Repeat flag, 1: repeat occurs
        key_value = (u32)data >> 0x1;
        addr      = (key_value & 0xFFFF00) >> 8; // customer code
        cmd_code  = key_value & 0x00FF; // command code
        cliPrintf("ir%u addr: [0x%x] cmd_code: [0x%x], repeat [0x%x]\n", group, addr, cmd_code, repeat);
    }
    return data;
}

static int ir_ut_test(CLI_t *cli, char *p)
{
    u32 group;
    u32 decode_mode;
    u32 customer_code = 0x00FF;

    if ((CliTokenCount(cli) == 2) || (CliTokenCount(cli) == 3))
    {
        if (CliTokenPopNum(cli, &group, 0) != eCLI_PARSE_OK)
            goto ir_help_exit;

        if (CliTokenPopNum(cli, &decode_mode, 0) != eCLI_PARSE_OK)
            goto ir_help_exit;

        if (decode_mode == 1)
            if (CliTokenPopNum(cli, &customer_code, 0) != eCLI_PARSE_OK)
                goto ir_help_exit;

        /* Configure the decoding mode of the IR device, the customer code and the callback function for receiving the IR signal */
        if (drv_ir_config(group, decode_mode, customer_code, ir_get_value))
            return eCLI_PARSE_ERROR;
    }
    else
    {
    ir_help_exit:
        cliPrintf("command format : ir [group] [decode_mode:1] [customer code(16bit)]\n");
        cliPrintf("command format : ir [group] [decode_mode:2 or 3] \n");
        return -eCLI_PARSE_INVALID_PARAMETER;
    }

    return eCLI_PARSE_OK;
}

6. API Reference

The header file is located at sc/driver/sysdriver/ir/drv/pub/drv_ir.h.

API Name	Function
drv_ir_config	Set the decoding mode of the IR device
drv_ir_key_dequeue	Get the customer code, command code, and repeat flag

typedef u32 (*ir_decode)(u32);
extern u64 drv_ir_key_dequeue(u32 group);
extern int drv_ir_config(u32 group, u32 decode_mode, u32 customer_code, ir_decode ir_handle);

6.1 drv_ir_config

• Purpose

  Set the decoding mode of the IR device, the customer code and the callback function for receiving IR signals.

• Syntax

  int drv_ir_config(u32 group, u32 decode_mode, u32 customer_code, ir_decode ir_handle)
  

• Parameter

  Parameter name	Value	Description
  group	0	IR device number
  decode_mode	1: Full, 2: Raw, 3: RC5	Decoding mode
  customer_code	16-Bit customer code	Only Full mode needs to be configured
  ir_handle	Function pointer	Used to respond to received IR signals

• Return value

  Return value	Description
  0	Success
  -7	IR device not supported

6.2 drv_ir_key_dequeue

• Purpose

  Get the customer code, command code, and repeat flag after decoding the IR signal.

• Syntax

  u64 drv_ir_key_dequeue(u32 group)
  

• Parameter

  Parameter name	Value	Description
  group	0	IR device number

• Return value

  Return value	Description
  data	BIT24-BIT9 is the customer code, BIT8-BIT1 is the command code, and BIT0 is the repeat flag

7. FAQ

7.1. IR Driver Cannot Receive IR Signal

• Check whether padmux has been configured, see 5.4. PADMUX Configuration.

• Check whether config is configured, see 5.2. CONFIG Configuration.

• Check whether the status of the SYSDESC IR node is ok.

• Check the remote control waveform to determine whether the IR_IN signal complies with the NEC and RC5 formats, and the current decoding mode matches the source signal.

• Check whether there is a place in the IR Receiver in the hardware schematic that needs to be shorted or a resistor is added (such as R1110/R1542 in Figure 6-1).

  

  Figure 6-1: IR Hardware Schematic