CONFIG USI - Revision history

Admin at 20:41, 13 December 2014

2014-12-13T20:41:31Z

Admin at 20:40, 13 December 2014

2014-12-13T20:40:26Z

Admin at 14:59, 4 February 2014

2014-02-04T14:59:58Z

Admin: Created page with "= Action = Configures the hardware USI. =
2014-02-04T14:58:16Z

Created page with "= Action = Configures the hardware USI. = <sp..."

New page
= Action =

Configures the hardware USI.

 

 

= Syntax =

CONFIG USI=mode , Address=adr

 

 

= Remarks =

The USI(universal serial Interface) is found in most atTiny processors. It can be used for various tasks. At the moment only the TWI slave mode is supported. The other modes you need to configure/code yourself.

The CONFIG USI = TWISLAVE mode requires a library that is part of the i2c slave add on which is a commercial add on.

 
<div style="padding: 0px; margin: 0px 0px 0px 4px;">
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Mode

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The supported mode is :

TWISLAVE. This will set the USI in TWI slave mode. The USI works in interrupt mode on the background.

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Address

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This is the I2C/TWI slave address. Notice that bascom uses the 8-bit address notation.

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When USI is used in TWI/I2C mode, it does require that SCL and SDA have pull up resistors. You can not freely choose the SCL and SDA pins : you must use the fixed SCL en SDA pins.

 

The variables  TWI_USI_OVS , TWI_slaveAddress, Twi , Twi_btr , TWI_bflag and Twi_btw are created by the compiler. These are all bytes

The USI interrupts are enabled but you need to enabled the global interrupt using ENABLE INTERRUPTS

 

The USI Slave code is running as an interrupt process. Each time there is an USI interrupt some slave code is executed. Your BASIC code is called from the low level slave code at a number of events.

You must include all these labels in your Slave application. You do not need to write code in all these sub routines.

 
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Label

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Event

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Twi_stop_rstart_received

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The Master sent a stop(i2CSTOP) or repeated start.

Typical you do not need to do anything here.

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Twi_addressed_goread

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The master has addressed the slave and will now continue to send data to the slave. You do not need to take action here.

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Twi_addressed_gowrite

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The master has addressed the slave and will now continue to receive data from the slave. You do not need to take action here.

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Twi_gotdata

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The master has sent data. The variable TWI holds the received value. The byte TWI_BTW is an index that holds the value of the number of received bytes. The first received byte will have an index value of 1.

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Twi_master_needs_byte

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The master reads from the slave and needs a value. The variable TWI_BTR can be inspected to see which index byte was needed.

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</div>
 

 

= See also =

[[Using_USI_(Universal_Serial_Interface)|Using USI]] , [[CONFIG_TWISLAVE|CONFIG TWISLAVE]], [[CONFIG_TWIXSLAVE|CONFIG TWIXSLAVE]]

 

 

= Example =

@@ Line 232: / Line 232: @@
   End Select 'you could also return the state of a port pin or A/D converter
 Return
-</source><br/>{{Languages}}
+</source>
 [[Category:BASCOM Language Reference]]

@@ Line 9: / Line 9: @@
 = <span class="f_Header">Syntax</span> =
-<span style="font-weight: bold; color: rgb(0, 0, 128);">CONFIG USI=</span>mode , Address=adr
+<span style="font-weight: bold; color: rgb(0, 0, 128);">CONFIG USI=</span>usimode , Address=adr
-<span style="font-family: Arial;">&nbsp;</span>
+<span style="font-weight: bold; color: rgb(0, 0, 128);">CONFIG USI=</span>usimode , Mode=mode
 <span style="font-family: Arial;">&nbsp;</span>
@@ Line 17: / Line 17: @@
 = <span class="f_Header">Remarks</span> =
-The USI(universal serial Interface) is found in most atTiny processors. It can be used for various tasks. At the moment only the TWI slave mode is supported. The other modes you need to configure/code yourself.
+The USI(universal serial Interface) is found in most atTiny processors. It can be used for various tasks. At the moment only the TWI slave and TWI master modes are supported. The other modes you need to configure/code yourself.
 The CONFIG USI = TWISLAVE mode requires a library that is part of the i2c slave add on which is a commercial add on.
 <span style="font-family: Arial;">&nbsp;</span>
@@ Line 26: / Line 28: @@
 |- style="vertical-align: top;"
 | valign="top" width="18%" style="width: 84px; border: 1px solid rgb(0, 0, 0);" |
-Mode
+usiMode
 | valign="top" width="103%" style="width: 392px; border: 1px solid rgb(0, 0, 0);" |
-The supported mode is :
+The supported mode is&nbsp;:
-TWISLAVE. This will set the USI in TWI slave mode. The USI works in interrupt mode on the background.
+-TWIMASTER. This will set the USI in TWI master mode. This mode does not use interrupts. The library i2c_usi.lib contains the USI master code.
 |- style="vertical-align: top;"
@@ Line 38: / Line 44: @@
 | valign="top" width="103%" style="width: 392px; border: 1px solid rgb(0, 0, 0);" |
-This is the I2C/TWI slave address. Notice that bascom uses the 8-bit address notation.
+This is the I2C/TWI slave address. Notice that bascom uses the 8-bit address notation. The address is only required when using the USI as a slave.
 |}
@@ Line 46: / Line 59: @@
 &nbsp;
-When USI is used in TWI/I2C mode, it does require that SCL and SDA have pull up resistors. You can not freely choose the SCL and SDA pins : you must use the fixed SCL en SDA pins.
+= <span class="f_Header">TWI SLAVE MODE</span> =
 &nbsp;
-The variables &nbsp;TWI_USI_OVS , TWI_slaveAddress, Twi , Twi_btr , TWI_bflag and Twi_btw are created by the compiler. These are all bytes
+The variables &nbsp;TWI_USI_OVS , TWI_slaveAddress, Twi , Twi_btr and Twi_btw are created by the compiler. These are all bytes.
 The USI interrupts are enabled but you need to enabled the global interrupt using ENABLE INTERRUPTS
@@ Line 59: / Line 74: @@
 You must include all these labels in your Slave application. You do not need to write code in all these sub routines.
 <span style="font-family: Arial;">&nbsp;</span>
@@ Line 112: / Line 129: @@
 <span style="font-family: Arial;">&nbsp;</span>
 = <span class="f_Header">See also</span> =
-<span style="font-family: Arial;">[[Using_USI_(Universal_Serial_Interface)|Using USI]]&nbsp;,&nbsp;[[CONFIG_TWISLAVE|CONFIG TWISLAVE]],&nbsp;[[CONFIG_TWIXSLAVE|CONFIG TWIXSLAVE]]</span>
+<span style="font-family: Arial;">[[Using USI (Universal Serial Interface)|Using USI]]&nbsp;,&nbsp;[[CONFIG TWISLAVE|CONFIG TWISLAVE]],&nbsp;[[CONFIG TWIXSLAVE|CONFIG TWIXSLAVE]]</span>
 <span style="font-family: Arial;">&nbsp;</span>
@@ Line 121: / Line 148: @@
 <span style="font-family: Arial;">&nbsp;</span>
-= <span class="f_Header">Example</span> =
+= <span class="f_Header">Example, USI SLAVE</span> =
 <source lang="bascomavr">

← Older revision		Revision as of 14:59, 4 February 2014
Line 122:		Line 122:

	= <span class="f_Header">Example</span> =		= <span class="f_Header">Example</span> =
		+
		+	<source lang="bascomavr">
		+	'-------------------------------------------------------------------------------
		+	' (c) 2004-2014 MCS Electronics
		+	' This demo demonstrates the USI I2C slave
		+	' Not all AVR chips have an USI !!!!
		+	'-------------------------------------------------------------------------------
		+
		+	$regfile = "attiny2313.dat"
		+
		+	$crystal = 8000000
		+	$hwstack = 40
		+	$swstack = 16
		+	$framesize = 24
		+
		+	const cPrint = 0 'make 0 for chips that have NO UART, make 1 when the micro has a UART and you want to show data on the terminal
		+
		+	#if cPrint
		+	$baud = 19200 'only when the processor has a UART
		+	#endif
		+
		+	config usi = twislave , address = &H40 'bascom uses 8 bit i2c address (7 bit shifted to the left with one bit)
		+
		+	#if cPrint
		+	print "USI DEMO"
		+	#endif
		+
		+	'do not forget to enable global interrupts since USI is used in interrupt mode
		+	enable interrupts 'it is important you enable interrupts
		+
		+	do
		+	! nop ; nothing to do here
		+	loop
		+
		+
		+
		+	'The following labels are called from the library. You need to insert code in these subroutines
		+	'Notice that the PRINT commands are remarked.
		+	'You can unmark them and see what happens, but it will increase code size
		+	'The idea is that you write your code in the called labels. And this code must execute in as little time
		+	'as possible. So when you slave must read the A/D converter, you can best do it in the main program
		+	'then the data is available when the master requires it, and you do not need to do the conversion which cost time.
		+
		+
		+	'A master can send or receive bytes.
		+	'A master protocol can also send some bytes, then receive some bytes
		+	'The master and slave address must match.
		+
		+	'the following labels are called from the library when master send stop or start
		+	Twi_stop_rstart_received:
		+	' Print "Master sent stop or repeated start"
		+	Return
		+
		+	'master sent our slave address and will not send data
		+	Twi_addressed_goread:
		+	' Print "We were addressed and master will send data"
		+	Return
		+
		+
		+	Twi_addressed_gowrite:
		+	' Print "We were addressed and master will read data"
		+	Return
		+
		+	'this label is called when the master sends data and the slave has received the byte
		+	'the variable TWI holds the received value
		+	Twi_gotdata:
		+	' Print "received : " ; Twi ; " byte no : " ; Twi_btw
		+	Select Case Twi_btw
		+	Case 1 : 'Portd = Twi ' first byte
		+	Case 2: 'you can set another port here for example
		+	End Select
		+	Return
		+
		+	'this label is called when the master receives data and needs a byte
		+	'the variable twi_btr is a byte variable that holds the index of the needed byte
		+	'so when sending multiple bytes from an array, twi_btr can be used for the index
		+	Twi_master_needs_byte:
		+	' Print "Master needs byte : " ; Twi_btr
		+	Select Case Twi_btr
		+	Case 1 : twi = 68 ' first byte
		+	Case 2 : twi = 69 ' send second byte
		+	End Select 'you could also return the state of a port pin or A/D converter
		+	Return
		+	</source><br/>{{Languages}}
		+
		+	[[Category:BASCOM Language Reference]]