CONFIG TWI - Revision history

Admin at 18:30, 17 January 2017

2017-01-17T18:30:02Z

Admin at 18:29, 17 January 2017

2017-01-17T18:29:36Z

Admin at 18:28, 17 January 2017

2017-01-17T18:28:43Z

Admin at 18:28, 17 January 2017

2017-01-17T18:28:03Z

Admin at 10:51, 24 August 2013

2013-08-24T10:51:59Z

Admin: Created page with "= Action = Configure the TWI (two wire serial interface). &n..."

2013-02-08T11:42:14Z

Created page with "= Action = Configure the TWI (two wire serial interface). &n..."

New page

= Action =

Configure the TWI (two wire serial interface).

 

 

= Syntax =

CONFIG TWI = clockspeed

CONFIG TWIC | TWID | TWIE | TWIF = clockspeed

 

(Config TWI is for ATMEGA and Config TWIX is for ATXMEGA chips)

 

= Remarks =
<div style="padding: 0px; margin: 0px 0px 0px 4px;">
{| width="485" cellspacing="0" cellpadding="1" border="1" style="border: 2px solid rgb(0, 0, 0); border-spacing: 0px; border-collapse: collapse;"
|- style="vertical-align: top;"
| valign="top" width="24%" style="width: 112px; border: 1px solid rgb(0, 0, 0);" |
clockspeed

| valign="top" width="100%" style="width: 364px; border: 1px solid rgb(0, 0, 0);" |
The desired clock frequency for SCL

|}
</div>
 

 

CONFIG TWI will set TWSR pre scaler bits 0 and 1, and TWBR depending on the used [[$CRYSTAL]] frequency and the desired SCL clock speed.

Typical you need a speed of 400 KHz. Some devices will work on 100 KHz as well.

 

When TWI is used in SLAVE mode, you need to have a faster clock speed as the master.

 

= XMEGA =

The XMEGA can contain up to 4 TWI units. When not specifying TWIC, TWID, TWIE or TWIF, the TWIC will be used as  the default.

You MUST dimension a variable named TWI_START as a byte. It is used by the xmega TWI library code. Without it, you will get an error.

 

There are 2 manuals available from ATMEL for every ATXMEGA Chip

 
<div style="padding: 0px; margin: 0px;">
{| border="0" cellpadding="0" cellspacing="0"
|- valign="baseline" style="vertical-align: baseline;"
| width="15" | 1.
| One Family Manual like for example for a ATXMEGA128A1 it is Atmel AVR XMEGA A Manual
|}
</div><div style="padding: 0px; margin: 0px;">
{| border="0" cellpadding="0" cellspacing="0"
|- valign="baseline" style="vertical-align: baseline;"
| width="15" | 2.
| Another Manual for the single chips like for example for an ATXMEGA128A1 it is the ATxmega64A1/128A1/192A1/256A1/384A1 Manual. In this Manual you find for example the Alternate Pin Functions. So you can find which Pin on Port C is the SDA and SCL Pin when you want to use the I2C/TWI Interface of this Port.
|}
</div>
 

 

[[File:Notice.jpg|left|Notice.jpg]] It is important that you specify the proper crystal frequency. Otherwise it will result in a wrong TWI clock frequency.

 

 

= See also =

[[$CRYSTAL]] , [[OPEN]]

 

 

= Example =

 <source lang="bascomavr">
'-----------------------------------------------------------------------
' (c) 2004 MCS Electronics
' This demo shows an example of the TWI
' Not all AVR chips have TWI (hardware I2C)
'------------------------------------------------------------------------

'The chip will work in TWI/I2C master mode
'Connected is a PCF8574A 8-bits port extender

$regfile="M8def.dat"' the used chip
$crystal= 4000000 ' frequency used
$baud= 19200 ' baud rate

$lib"i2c_twi.lbx"' we do not use software emulated I2C but the TWI

Config Scl =Portc.5 ' we need to provide the SCL pin name
Config Sda =Portc.4 ' we need to provide the SDA pin name

'On the Mega8, On the PCF8574A
'scl=PC5 , pin 28 pin 14
'sda=PC4 , pin 27 pin 15

I2cinit' we need to set the pins in the proper state

Config Twi = 100000 ' wanted clock frequency
'will set TWBR and TWSR
'Twbr = 12 'bit rate register
'Twsr = 0 'pre scaler bits

Dim B AsByte, X AsByte
Print"TWI master"
Do
Incr B ' increase value
I2csend&B01110000 , B ' send the value
Print"Error : ";Err' show error status
I2creceive&B01110000 , X ' get a byte
Print X ;" ";Err' show error
Waitms 500 'wait a bit
Loop
End
</source> {{Languages}}

[[Category:BASCOM Language Reference]]

@@ Line 57: / Line 57: @@
 [[File:Notice.jpg|notice]]To use the hardware I2C routines and not the Software I2C routines you need to use the<span style="font-size: 8pt; font-family: 'Courier'; font-weight: bold; color: #000080;">$lib</span><span style="font-size: 8pt; font-family: 'Courier'; color: #008080;">"i2c_twi.lbx"</span><span style="font-size: 8pt; font-family: 'Courier';">! (NOT FOR XMEGA)</span>
-<span style="font-size: 8pt; font-family: 'Courier';"></span><span style="font-size: 10pt;">Some processors support multiple TWI interfaces like the MEGA328PB. Use CONFIG TWI1 to configure the second TWI named TWI1. The first TWI which is named TWI0 is referred to as TWI.</span>
 = <span class="f_Header">XMEGA</span> =

@@ Line 55: / Line 55: @@
 [[File:Notice.jpg|notice]]There is no dynamic channel support for I2C
-[[File:Notice.jpg|notice]]To use the hardware I2C routines and not the Software I2C routines you need to use the<span class="f_ImageCaption"></span><span style="font-size: 8pt; font-family: 'Courier'; font-weight: bold; color: #000080;">$lib</span><span style="font-size: 8pt; font-family: 'Courier';"></span><span style="font-size: 8pt; font-family: 'Courier'; color: #008080;">"i2c_twi.lbx"</span><span style="font-size: 8pt; font-family: 'Courier';">! (NOT FOR XMEGA)</span>
+[[File:Notice.jpg|notice]]To use the hardware I2C routines and not the Software I2C routines you need to use the<span style="font-size: 8pt; font-family: 'Courier'; font-weight: bold; color: #000080;">$lib</span><span style="font-size: 8pt; font-family: 'Courier'; color: #008080;">"i2c_twi.lbx"</span><span style="font-size: 8pt; font-family: 'Courier';">! (NOT FOR XMEGA)</span>
 = <span class="f_Header">XMEGA</span> =

← Older revision		Revision as of 18:28, 17 January 2017
Line 52:		Line 52:


		+
		+	[[File:Notice.jpg\|notice]]There is no dynamic channel support for I2C
		+
		+	[[File:Notice.jpg\|notice]]To use the hardware I2C routines and not the Software I2C routines you need to use the<span class="f_ImageCaption"></span><span style="font-size: 8pt; font-family: 'Courier'; font-weight: bold; color: #000080;">$lib</span><span style="font-size: 8pt; font-family: 'Courier';"></span><span style="font-size: 8pt; font-family: 'Courier'; color: #008080;">"i2c_twi.lbx"</span><span style="font-size: 8pt; font-family: 'Courier';">! (NOT FOR XMEGA)</span>

	= <span class="f_Header">XMEGA</span> =		= <span class="f_Header">XMEGA</span> =

@@ Line 10: / Line 10: @@
 <span class="f_Syntax">CONFIG TWI&nbsp;</span>= clockspeed
 <span class="f_Syntax">CONFIG TWIC | TWID | TWIE | TWIF&nbsp;</span>= clockspeed
@@ Line 15: / Line 23: @@
 &nbsp;
-<span style="font-family: Arial;">(Config TWI is for ATMEGA and Config TWI</span><span style="font-family: Arial; font-weight: bold;">X</span><span style="font-family: Arial;">&nbsp;is for ATXMEGA chips)</span>
+<span style="font-family: Arial;">(Config TWI and TWI1 is for ATMEGA and Config TWI</span><span style="font-family: Arial; font-weight: bold;">X</span><span style="font-family: Arial;">is for ATXMEGA chips)</span>
 <span style="font-family: Arial;">&nbsp;</span>

@@ Line 134: / Line 134: @@
 Loop
 End
-</source><br/>{{Languages}}
+</source>
 [[Category:BASCOM Language Reference]]