i2c

Documentation

Overview

Package i2c implements a driver for NXP I2C controllers adopting the following reference specifications:

• IMX6ULLRM - i.MX 6ULL Applications Processor Reference Manual - Rev 1 2017/11
• IMX6FG - i.MX 6 Series Firmware Guide - Rev 0 2012/11

This package is only meant to be used with `GOOS=tamago GOARCH=arm` as supported by the TamaGo framework for bare metal Go on ARM SoCs, see https://github.com/usbarmory/tamago.

Index

• Constants
• type I2C
  • func (hw *I2C) Init()
  • func (hw *I2C) Read(target uint8, addr uint32, alen int, size int) (buf []byte, err error)
  • func (hw *I2C) Write(buf []byte, target uint8, addr uint32, alen int) (err error)

Constants

const (
	// The default IFDR value corresponds to a frequency divider of 768,
	// assuming 66 MHz for PERCLK_CLK_ROOT this results in a baud rate of
	// 85 kbps (p1464, 31.7.2 I2C Frequency Divider Register (I2Cx_IFDR),
	// IMX6ULLRM).
	I2C_DEFAULT_IFDR = 0x16

	I2Cx_IADR = 0x0000
	I2Cx_IFDR = 0x0004

	I2Cx_I2CR = 0x0008
	I2CR_IEN  = 7
	I2CR_MSTA = 5
	I2CR_MTX  = 4
	I2CR_TXAK = 3
	I2CR_RSTA = 2

	I2Cx_I2SR = 0x000c
	I2SR_IBB  = 5
	I2SR_IIF  = 1
	I2SR_RXAK = 0

	I2Cx_I2DR = 0x0010
)

I2C registers (p1462, 31.7 I2C Memory Map/Register Definition, IMX6ULLRM)

const (
	// Timeout is the default timeout for I2C operations.
	Timeout = 100 * time.Millisecond
)

Configuration constants

Types

type I2C

type I2C struct {
	sync.Mutex

	// Controller index
	Index int
	// Base register
	Base uint32
	// Clock gate register
	CCGR uint32
	// Clock gate
	CG int
	// Timeout for I2C operations
	Timeout time.Duration
	// Div sets the frequency divider to control the I2C clock rate
	// (p1464, 31.7.2 I2C Frequency Divider Register (I2Cx_IFDR), IMX6ULLRM).
	Div uint16
	// contains filtered or unexported fields
}

I2C represents an I2C port instance.

func (*I2C) Init

func (hw *I2C) Init()

Init initializes the I2C controller instance. At this time only master mode is supported by this driver.

func (*I2C) Read

func (hw *I2C) Read(target uint8, addr uint32, alen int, size int) (buf []byte, err error)

Read reads a sequence of bytes from a target device (p167, 16.4.2 Programming the I2C controller for I2C Read, IMX6FG).

The return data buffer always matches the requested size, otherwise an error is returned.

The address length (`alen`) parameter should be set greater then 0 for ordinary I2C reads (`SLAVE W|ADDR|SLAVE R|DATA`), equal to 0 when not sending a register address (`SLAVE W|SLAVE R|DATA`) and less than 0 only to send a target read (`SLAVE R|DATA`).

func (*I2C) Write

func (hw *I2C) Write(buf []byte, target uint8, addr uint32, alen int) (err error)

Write writes a sequence of bytes to a target device (p170, 16.4.4 Programming the I2C controller for I2C Write, IMX6FG)

Set greater then 0 for ordinary I2C write (`SLAVE W|ADDR|DATA`), set equal then 0 to not send register address (`SLAVE W|DATA`), alen less then 0 is invalid.

The address length (`alen`) parameter should be set greater then 0 for ordinary I2C writes (`SLAVE W|ADDR|DATA`), equal to 0 when not sending a register address (`SLAVE W|DATA`), values less than 0 are not valid.