# I2C Usage Instructions ## Overview The K230 SoC integrates 5 Synopsys DesignWare I2C controllers, with details as follows: | I2C Controller | Base Address | Default Clock Frequency | Default State | |------------|------------|--------------|----------| | I2C0 | 0x91405000 | 100kHz | disabled | | I2C1 | 0x91406000 | 400kHz | disabled | | I2C2 | 0x91407000 | 400kHz | disabled | | I2C3 | 0x91408000 | 400kHz | disabled | | I2C4 | 0x91409000 | 400kHz | disabled | > **Note**: All I2C controllers are `disabled` by default and must be enabled in the device tree before use. ## Device Tree Configuration ### Device Tree Alias Configuration Define I2C bus aliases in the `aliases` node of the device tree, making it easy for the kernel and other device tree files to reference them. **CanMV-K230 Development Board Example:** ```dts aliases { serial3 = &uart3; i2c0 = &i2c4; // Corresponds to /dev/i2c-0 i2c1 = &i2c3; // Corresponds to /dev/i2c-1 mmc0 = &mmc_sd0; mmc1 = &mmc_sd1; }; ``` **Description:** - The alias names (`i2c0`, `i2c1`) are defined by the kernel or board-level configuration - The aliases point to specific I2C controller nodes (`&i2c4`, `&i2c3`) - The kernel creates corresponding numbered I2C buses based on the aliases, and device nodes can reference them via `&i2c0` - This approach improves the portability of the device tree, eliminating the need to modify all references when board-level configuration changes ### Enabling the I2C Controller ```dts &i2c2 { status = "okay"; pinctrl-names = "default"; pinctrl-0 = <&i2c2_pins>; clock-frequency = <400000>; // 400kHz Fast Mode }; ``` ### Configuring Pin Multiplexing ```dts &iomux { i2c2_pins: i2c2_pins { pins = K230_IO11, K230_IO12; function = "alt3"; bias-pull-up; }; }; ``` ### Adding I2C Device Nodes Add device nodes under the enabled I2C bus: ```dts &i2c2 { status = "okay"; // Example: Add 24C02 EEPROM eeprom@50 { compatible = "atmel,24c02"; reg = <0x50>; }; // Example: Add TMP102 temperature sensor tmp102@48 { compatible = "ti,tmp102"; reg = <0x48>; }; }; ``` ### CanMV-K230 Complete Configuration Example Reference file: `arch/riscv/boot/dts/canaan/k230-canmv-01studio.dts` ```dts // Initialize aliases aliases { serial3 = &uart3; i2c0 = &i2c4; i2c1 = &i2c3; mmc0 = &mmc_sd0; mmc1 = &mmc_sd1; }; // Pin configuration &iomux { i2c2_pins: i2c2_pins { pins = K230_IO11, K230_IO12; function = "alt3"; }; }; // Enable I2C3 (used for LT9611 HDMI bridge) &i2c3 { status = "okay"; lt9611: hdmi-bridge@3b { compatible = "lontium,lt9611"; reg = <0x3b>; reset-gpios = <&gpio0_ports 22 GPIO_ACTIVE_HIGH>; interrupt-parent = <&gpio0_ports>; interrupts = <23 IRQ_TYPE_EDGE_FALLING>; }; }; // Enable I2C4 &i2c4 { status = "okay"; }; ``` ## Userspace Operations ### List I2C Buses ```bash i2cdetect -l ``` Example output: ```bash [root@canaan ~]# i2cdetect -l i2c-1 i2c Synopsys DesignWare I2C adapter I2C adapter i2c-2 i2c Synopsys DesignWare I2C adapter I2C adapter i2c-0 i2c Synopsys DesignWare I2C adapter I2C adapter ``` ### Scan I2C Devices ```bash i2cdetect -y -r -a 2 ``` Example output: ```bash 0 1 2 3 4 5 6 7 8 9 a b c d e f 00: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 10: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 20: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 30: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 40: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 50: 50 -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 60: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 70: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- ``` ### Read Register ```bash # Read a single byte: from the device at address 0x50 on I2C bus 2, read data at offset 0x00 i2cget -y 2 0x50 0x00 # Read byte data from the specified register (b = byte) i2cget -y 2 0x50 0x01 b # Read word data (w = word, 16-bit) i2cget -y 2 0x50 0x00 w ``` ### Write Register ```bash # Write a single byte i2cset -y 2 0x50 0x00 0x55 # Write word data (w = word) i2cset -y 2 0x50 0x00 0x1234 w ``` ### Device File Interface I2C devices appear in `/dev/` as follows: ```bash ls -l /dev/i2c-* ``` Example output: ```bash crw-rw---- 1 root i2c 89, 0 Jun 10 10:00 /dev/i2c-0 crw-rw---- 1 root i2c 89, 1 Jun 10 10:00 /dev/i2c-1 ``` ## Programming Examples ### C Language Example ```c #include #include #include #include #include #include #include void print_usage(const char *prog) { printf("Usage: %s [I2C_BUS]\n", prog); printf(" -h, --help Show this help message\n"); printf(" I2C_BUS I2C bus device (default: /dev/i2c-0)\n"); } int main(int argc, char *argv[]) { // 解析 -h 参数 for (int i = 1; i < argc; i++) { if (strcmp(argv[i], "-h") == 0 || strcmp(argv[i], "--help") == 0) { print_usage(argv[0]); return 0; } } int file; char *filename = "/dev/i2c-0"; if (argc > 1) { filename = argv[1]; } // 打开 I2C 设备 file = open(filename, O_RDWR); if (file < 0) { perror("Failed to open i2c device"); return -1; } printf("Scanning I2C bus: %s\n", filename); printf("Address Device\n"); printf("------- ------\n"); printf("\n7-bit addresses (0x00-0xff):\n"); // 扫描所有 0x00 到 0xFF 的地址 for (int addr = 0x00; addr <= 0xFF; addr++) { // 设置从设备地址 if (ioctl(file, I2C_SLAVE, addr) < 0) { continue; } // 尝试读取 1 个字节 // 此操作是安全的，不会影响设备状态 unsigned char buf[1]; int result = read(file, buf, 1); // 如果读取成功，说明设备存在 if (result == 1) { printf(" 0x%02X Present\n", addr); } } printf("\nNote: 0x78-0x7F are reserved addresses.\n"); close(file); return 0; } ``` ### Python Example #### Using Adafruit Blinka busio ```python import time import sys import board import busio def main(bus_num=0): """Scan I2C devices on specified bus.""" # SCL and SDA pins for different I2C buses print(f"Hello Blinka! Using I2C bus {bus_num}") _, scl, sda = board.pin.i2cPorts[bus_num] i2c = busio.I2C(scl, sda) while not i2c.try_lock(): pass try: devices = i2c.scan() print(f"I2C devices found on bus {bus_num}: {[hex(i) for i in devices]}") finally: i2c.unlock() if __name__ == "__main__": bus = 0 if len(sys.argv) > 1: if sys.argv[1] in ["-h", "--help"]: print("Usage: python pi_busio_i2c.py [bus_num]") print(" bus_num I2C bus number (default: 0)") print(" 0 - I2C0 (SCL/SDA)") print(" 1 - I2C1 (SCL1/SDA1)") print(" 2 - I2C2 (SCL2/SDA2)") sys.exit(0) bus = int(sys.argv[1]) main(bus) ``` #### Scanning Devices Without Libraries ```python #!/usr/bin/env python3 import fcntl import sys I2C_SLAVE = 0x0703 def i2c_scan(bus_num=0): with open(f"/dev/i2c-{bus_num}", "r+b", buffering=0) as f: print(f"Scanning I2C bus {bus_num}:") print("Address Device") print("------- ------") for addr in range(0x00, 0x100): try: fcntl.ioctl(f.fileno(), I2C_SLAVE, addr) f.read(1) # 尝试读取一个字节 print(f" 0x{addr:02X} Present") except: pass if __name__ == "__main__": if len(sys.argv) > 1 and sys.argv[1] in ["-h", "--help"]: print("Usage: python i2c.py [bus_num]") print(" bus_num I2C bus number (default: 0)") print(" -h, --help Show this help message") sys.exit(0) bus = 0 if len(sys.argv) > 1: bus = int(sys.argv[1]) i2c_scan(bus) ``` ## Related Files - Device tree file: `arch/riscv/boot/dts/canaan/k230.dtsi` - Platform driver: `drivers/i2c/busses/i2c-designware-platdrv.c` - Core driver: `drivers/i2c/busses/i2c-designware-core.h` - Kconfig: `drivers/i2c/busses/Kconfig`