135 lines
4.2 KiB
Markdown
135 lines
4.2 KiB
Markdown
Helios64 supports I2C bus for low-speed communication between devices like microcontrollers, EEPROMs, A/D and D/A converters, I/O interfaces and other similar peripherals. In order to communicate with each I2C slave device you will need an address and communication scenario.
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## I2C bus on Helios64 / RK3399
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The I2C controller on RK3399 supports following features:
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- 9 on-chip I2C controllers
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- Multi-master I2C operation
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- Support 7bits and 10bits address mode
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- Serial 8bits oriented and bidirectional data transfers can be made
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- Software programmable clock frequency
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- Data on the I2C-bus can be transferred at rates of up to 100 kbit/s in the Standardmode, up to 400 kbit/s in the Fast-mode or up to 1 Mbit/s in Fast-mode Plus
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**Note:** In the implementation we divided the I2C controller into 2 categories:
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* Internal Bus, reserved for the system
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* Externel Bus, allocated for user application
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## Internal Bus
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!!! Warning
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Theses buses and addresses should not be accessed directly by user. Incorrect configuration can damage the board.
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Bus 0:
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Slave | Address | Description|
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------- | ------ |------ |
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RK808-D | 0x1b | |
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SYR837 | 0x40 | |
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SYR838 | 0x41 | |
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Bus 2:
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Slave | Address | Description|
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------- | ------ |------ |
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NCT75 | 0x4c | |
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PCA9655 | 0x21 | |
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Bus 4:
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Slave | Address | Description|
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------- | ------ |------ |
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FUSB302 | 0x22 | |
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Above list also includes buses number 1,3,5 which are reserved for system use, therefore not accessible to the user.
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## External Bus
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Helios64 exposes Bus number 7 and 8 respectively on **P2** and **P1** headers.
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All the I2C buses on the board are using voltage level of 3.3V. Note that Helios64 is integrated with level translator and pull up resistor.
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Please take caution of the reserved address when you use the I2C interface, below is the reserved address list:
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Slave Address | R/W Bit | Description
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--------------|---------|-------------------
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000 0000 | 0 | General call address
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000 0000 | 1 | START byte(1)
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000 0001 | X | CBUS address(2)
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000 0010 | X | Reserved for different bus format (3)
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000 0011 | X | Reserved for future purposes
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000 01XX | X | Hs-mode master code
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111 10XX | X | 10-bit slave addressing
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111 11XX | X | Reserved for future purposes
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### I2C Header (P1)
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Helios64 board exposes I2C Bus 8 on header P1.
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This I2C device works with 3 pin bus (SDA, SCL, and GND), and also in band addressing. Below is the header pin-out:
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### UEXT Header (P2)
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The I2C Bus 7 can be found on the [UEXT header (P2)](/helios64/uext/).
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Below is the full pinout of the UEXT header:
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Pin No | Description
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--------|-------------
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1|3.3V
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2|GND
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3|TXD (UART)
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4|RXD (UART)
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5|SCL (I2C)
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6|SDA (I2C)
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7|MISO (SPI)
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8|MOSI (SPI)
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9|SCK (SPI)
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10|SSEL (SPI)
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## Usage under Linux
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Below table list the I2C external bus device name as detected under Linux:
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Bus number | Device Block | Description |
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-----------|--------------|--------------|
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7 | /dev/i2c-7 | |
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8 | /dev/i2c-8 | |
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### Checking the I2C Communication under linux
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In order to communicate with the I2C devices, first we need to identify the I2C bus. By performing scan you can see whether the system can detect device.
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1. Install the Linux i2c tools.
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```
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$ sudo apt-get install i2c-tools
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```
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2. Use **i2cdetect** tool to scan I2C Bus 8.
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```
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root@helios64:~# i2cdetect -y 8
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0 1 2 3 4 5 6 7 8 9 a b c d e f
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00: -- -- -- -- -- -- -- -- -- -- -- -- --
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10: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
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20: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
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30: -- -- -- -- -- -- -- -- -- -- -- -- 3c -- -- --
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40: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
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50: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
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60: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
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70: -- -- -- -- -- -- -- --
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```
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Here we can see there is a device detected at the address 0x3c. If you have connected more than just one I2C device on the **P1** header, there will be more devices with different addresses detected on the bus.
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