README
¶
HD44780 over I2C
This provides control of an HD44780-compatible device that is connected via an I2C expander.
Usage
Import the packages:
// import the require modules
import(
"github.com/mrmorphic/hwio"
"github.com/mrmorphic/hwio/devices/hd44780"
)
Initialise by fetching an i2c module from the driver. You can get instances of devices attached to the bus.
// Get the i2c module from the driver. i2c is the canonical name. On the BeagleBone, it can also
// be referred to as i2c2.
m, e := hwio.GetModule("i2c")
// Assert that it is an I2C module
i2c := m.(hwio.I2CModule)
Get the HD44780 device, so you make requests of it:
// Get a display device on this i2c bus. You need to provide it a device profile. Two profiles
// are currently implemented, PROFILE_MJKDZ and PROFILE_PCF8574, corresponding to two commonly found
// port extenders used to interface to LCD displays.
display := hd44780.NewHD44780(i2c, 0x20, hd44780.PROFILE_MJKDZ)
// Initialise the display with the size of display you have.
display.Init(20, 4)
// The display may not show anything if the backlight is turned off
display.SetBacklight(true)
// If you want to see the cursor, you can turn it on
display.Cursor()
To display things, you can:
// clear the display
display.Clear()
// Set cursor back to (0,0)
display.Home()
// Set cursor to a specific column and row (both zero based)
display.SetCursor(0, 1) // second line
// output a single character
display.Data('A')
// Use any function that expects a Writer to output to the display. This is because the HD44780 type
// implements Writer interface.
fmt.Fprintf(display, "Hi, %s", name)
Note that characters that are output to the device are not necessarily displayed consequetively. In particular wrapping may not work as you expect. This is because of how the display unit maps it's display buffer to positions on the screen. This is described in the datasheet for the HD44780 unit.
An alternative way to create the device is to use NewHD44780Extended instead of NewHD44780. This is useful if you have an i2c extender that does not confirm to the builtin profiles:
display := NewHD44780Extended(i2c, 0x27,
0, // en
1, // rw
2, // rs
4, // d4
5, // d5
6, // d6
7, // d7polarity int) *HD44780 {
3, // backlight,
hd44780.POSITIVE) // polarity
The pin values are the bit positions for that pin, with 7 being MSB and0 being LSB. The underlying assumption is that the port extender is 8 bit. This package will not work for 16 bit extenders, for example.
Notes
This has been tested on an mjkdz i2c expander and a 20x4 character display, and works correctly. Other LCD i2c expanders may map En, Rw and Rs pins differently, however. If you have issues with a different I2C device, let me know, or submit a pull request with the configuration that works for you.
Documentation
¶
Index ¶
- Constants
- type HD44780
- func (display *HD44780) Autoscroll()
- func (display *HD44780) Blink()
- func (display *HD44780) Clear()
- func (display *HD44780) Command(command byte)
- func (display *HD44780) Cursor()
- func (display *HD44780) Data(data byte)
- func (display *HD44780) Display()
- func (display *HD44780) Home()
- func (display *HD44780) Init(cols int, lines int)
- func (display *HD44780) LeftToRight()
- func (display *HD44780) NoAutoscroll()
- func (display *HD44780) NoBlink()
- func (display *HD44780) NoCursor()
- func (display *HD44780) NoDisplay()
- func (display *HD44780) RightToLeft()
- func (display *HD44780) ScrollDisplayLeft()
- func (display *HD44780) ScrollDisplayRight()
- func (display *HD44780) SetBacklight(on bool)
- func (display *HD44780) SetCursor(col int, row int)
- func (display *HD44780) Write(p []byte) (n int, err error)
- type I2CExpanderProfile
Constants ¶
const ( // commands LCD_CLEARDISPLAY byte = 0x01 LCD_RETURNHOME byte = 0x02 LCD_ENTRYMODESET byte = 0x04 LCD_DISPLAYCONTROL byte = 0x08 LCD_CURSORSHIFT byte = 0x10 LCD_FUNCTIONSET byte = 0x20 LCD_SETCGRAMADDR byte = 0x40 LCD_SETDDRAMADDR byte = 0x80 // flags for display entry mode LCD_ENTRYRIGHT byte = 0x00 LCD_ENTRYLEFT byte = 0x02 LCD_ENTRYSHIFTINCREMENT byte = 0x01 LCD_ENTRYSHIFTDECREMENT byte = 0x00 // flags for display on/off control LCD_DISPLAYON byte = 0x04 LCD_DISPLAYOFF byte = 0x00 LCD_CURSORON byte = 0x02 LCD_CURSOROFF byte = 0x00 LCD_BLINKON byte = 0x01 LCD_BLINKOFF byte = 0x00 // flags for display/cursor shift LCD_DISPLAYMOVE byte = 0x08 LCD_CURSORMOVE byte = 0x00 LCD_MOVERIGHT byte = 0x04 LCD_MOVELEFT byte = 0x00 // flags for function set LCD_8BITMODE byte = 0x10 LCD_4BITMODE byte = 0x00 LCD_2LINE byte = 0x08 LCD_1LINE byte = 0x00 LCD_5x10DOTS byte = 0x04 LCD_5x8DOTS byte = 0x00 // constants for backlight polarity POSITIVE = 0 NEGATIVE = 1 )
Variables ¶
This section is empty.
Functions ¶
This section is empty.
Types ¶
type HD44780 ¶
type HD44780 struct {
// contains filtered or unexported fields
}
func NewHD44780 ¶
func NewHD44780(module hwio.I2CModule, address int, profile I2CExpanderProfile) *HD44780
func NewHD44780Extended ¶
func (*HD44780) Autoscroll ¶
func (display *HD44780) Autoscroll()
This will 'right justify' text from the cursor
func (*HD44780) LeftToRight ¶
func (display *HD44780) LeftToRight()
This is for text that flows Left to Right
func (*HD44780) NoAutoscroll ¶
func (display *HD44780) NoAutoscroll()
This will 'left justify' text from the cursor
func (*HD44780) RightToLeft ¶
func (display *HD44780) RightToLeft()
This is for text that flows Right to Left
func (*HD44780) ScrollDisplayLeft ¶
func (display *HD44780) ScrollDisplayLeft()
These commands scroll the display without changing the RAM
func (*HD44780) ScrollDisplayRight ¶
func (display *HD44780) ScrollDisplayRight()
func (*HD44780) SetBacklight ¶
type I2CExpanderProfile ¶
type I2CExpanderProfile int
const ( // mjkdz devices are commonly found in the wild PROFILE_MJKDZ I2CExpanderProfile = iota // devices based on PCF8574 are also around, but wired a little bit differently. PROFILE_PCF8574 )
Source Files