CONFIG COMx

Action

Configures the UART of AVR chips that have an extended UART like the M2560.

Syntax

Syntax Xmega

CONFIG COMx = baud , Mode=mode, Parity=parity, Stopbits=stopbits, Databits=databits

Syntax Xtiny

CONFIG COMx = baud , Mode=mode, Parity=parity, Stopbits=stopbits, Databits=databits , Baud_Offset=baud_ofs , TXPIN=tx

Remarks normal AVR

COMx	The COM port to configure. Value in range from 1-4
baud	Baud rate to use.
synchrone	0 for asynchrone operation (default) and 1 for synchrone operation.
Parity	None, disabled, even or odd
Stopbits	The number of stop bits : 1 or 2
Databits	The number of data bits : 4,5,7,8 or 9.
Clockpol	Clock polarity. 0 or 1.

Note that not all AVR chips have the extended UART. Most AVR chips have a UART with fixed communication parameters. These are : No parity, 1 stopbit, 8 data bits.

The Mega2560 does support 4 UART's.

Remarks Xmega

COMx	The COM port to configure. Value in range from 1-8
baud	Baud rate to use. If the baud rate can be generated accurately depends on the system clock.
mode	The USART mode, this can be : - ASYNCHRONEOUS or 0 (default) for asynchronous operation. - SYNCHRONEOUS or 1 , for synchronous operation. - IRDA or IRCOM for IRDA operation - SPI or MSPI for operation as SPI controller * The mode must be provided since the baud calculation depends on the selected mode *
Parity	None, disabled, even or odd
Stopbits	The number of stop bits : 1 or 2
Databits	The number of data bits : 5,6,7,8 or 9.

In the Xmega the registers have a fixed offset. This allows to use dynamic UARTS : you can change settings at run time by using a variable. This will use some more code when using just one UART but will save code when using multiple UARTS because you need only one copy of the code.

In the Xmega you MUST use CONFIG COM before you can use the UART. The CONFIG commands makes a call to _INIT_XMEGA_UART where the various parameters are passed to setup the UART. You also need to specify the baud rate. Do not use $BAUD.

The CLOCKPOL for the SPI mode has been removed, it will be added to a configuration command for the SPI.

The CONFIG COM will set the TX pin to output mode. This are the following pins :

UART	TX pin	RX pin	BAUD
COM1 - UART_C0	PORTC.3	PORTC.2	BAUD
COM2 - UART_C1	PORTC.7	PORTC.6	BAUD1
COM3 - UART_D0	PORTD.3	PORTD.2	BAUD2
COM4 - UART_D1	PORTD.7	PORTD.6	BAUD3
COM5 - UART_E0	PORTE.3	PORTE.2	BAUD4
COM6 - UART_E1	PORTE.7	PORTE.6	BAUD5
COM7 - UART_F0	PORTF.3	PORTF.2	BAUD6
COM8 - UART_F1	PORTF.7	PORTF.6	BAUD7

In IRDA mode, depending on the module you use, it might be necessary to invert the logic level of the TX pin with CONFIG XPIN. For example when COM1 is used for the IRDA module, you would use : CONFIG XPIN=PORTC.3, INVERTIO=ENABLED

Remarks XTINY/MEGAX

COMx	The COM port to configure. Value in range from 1-4
baud	Baud rate to use. If the baud rate can be generated accurately depends on the system clock.
mode	The USART mode, this can be : - ASYNCHRONEOUS : (default) for asynchronous operation. - SYNCHRONEOUS : for synchronous operation. - IRCOM : for IRDA operation - SPI : for operation as SPI controller * The mode must be provided since the baud calculation depends on the selected mode *
Parity	None, disabled, even or odd
Stopbits	The number of stop bits : 1 or 2
Databits	The number of data bits : 5,6,7,8 or 9.
Baud_offset	The Xtiny has an internal oscillator that runs at 16 or 20 MHz. The center frequency can be off depending on temperature and voltage. The Xtiny has 4 calibrated offset values for the oscillator which can be used to correct the BAUD. The options are : - NONE : default, BAUD is calculated but no offset is used. All of the other values will read the signature row and will call code from xtiny.lib to compensate the BAUD value. - OSC16_3V3 : OSC runs at 16 MHz and at 3V3 - OSC16_5V : OSC runs at 16 MHz and at 5V - OSC20_3V3 : OSC runs at 20 MHz and at 3V3 - OSC20_5V : OSC runs at 20 MHz and at 5V It is up to the user to apply the selected voltage. It is up to the user to use the specified oscillator value. (change fuse bits). By default the 20 MHz internal osc is selected. So this setting does not change oscillator values, it only tells the compiler which sigrow must be loaded and used.
TXPIN	This options selects the pins used for the UART. The XTINY/MEGAX has a port multiplexer. This multi plexer allows to chose which pins are used for hardware connected to the port pins. So this allows to chose one or more alternative pin locations for hardware such as USART,SPI, TWI and TIMER output. You can use CONFIG PORT_MUX when you use alternative pin positions. But CONFIG PORT_MUX does not set port direction. For the USART it is required to set the TX pin into output mode. That is why this option exists : you can chose the alternative pin location and the compiler will set the port pin into output mode and will set the proper port multiplexer register bit. You can chose between the default location starting with DEF_ and the alternative location starting with ALTx_ Some processors also allow to disconnect the pins totally and they have a NONE option. Please note that you only should use this option when you use the alternative pin location.

It is preferred to use CONFIG COM instead of using $BAUD.

It is important that you specify all parameters of CONFIG COM. Do not omit one. The only optional parameter is TXPIN for the alternative TX pin.