usart.c File Reference

---

Detailed Description

PDC and interrupt control example application.

This file gives an example of using the PDC to burst data on the USART. With and without the use of interrupts.

• Compiler: IAR EWAAVR32 and GNU GCC for AVR32
• Supported devices: All AVR32 devices with PDC and USART module.
• AppNote: AVR32108 - Peripheral Direct Memory Access Driver

Author:

Atmel Corporation: http://www.atmel.com
Support email: avr32@atmel.com

Name

RELEASE_1_0

Revision

1.9

RCSfile

usart.c,v

Date

2006/05/09 10:32:56

Definition in file usart.c.

#include "usart.h"

Include dependency graph for usart.c:

Go to the source code of this file.

Functions
int	usart_linit (volatile struct avr32_usart_t *usart, const struct usart_options_t *opt, const long cpuHz)
	Setup the usart to use the standard RS232 protocol.
int	usart_lwriteLine (volatile struct avr32_usart_t *usart, const char *string)
	write one character string to the usart
int	usart_putchar (volatile struct avr32_usart_t *usart, const int character)
	Send a character with the usart.
void	usart_reset (volatile struct avr32_usart_t *usart)
	This function will reset the USART, and disable TX and RX.
static int	usart_set_baudrate (volatile struct avr32_usart_t *usart, unsigned int baudrate, const long cpuHz)
	This function will calculate a clock divider(CD) and fractional part(FP) that gets the usart as close to a wanted baudrate as possible.

---

Function Documentation

int usart_linit (  volatile struct avr32_usart_t *  usart, const struct usart_options_t *  opt, const long  cpuHz )

Setup the usart to use the standard RS232 protocol. Parameters: usart  base address of the usart opt  options needed to set up RS232 communcation (see usart_options_t) cpuHz  frequency of the selected clock Returns: status Return values: USART_OK  on success USART_ERROR_ARGUMENT  on wrong arguments Definition at line 147 of file usart.c. References usart_options_t::baudrate, usart_options_t::channelmode, usart_options_t::charlength, usart_options_t::paritytype, usart_options_t::stopbits, USART_ERROR_ARGUMENT, USART_OK, usart_reset(), and usart_set_baudrate(). Referenced by main(). { int retval; /* reset the usart and shutdown RX and TX */ usart_reset(usart); /* control input values */ if (opt == 0) { return USART_ERROR_ARGUMENT; } if (opt->charlength < 5 || opt->charlength > 9) { return USART_ERROR_ARGUMENT; } if (opt->paritytype > 7) { return USART_ERROR_ARGUMENT; } if (opt->stopbits > 2+255) { return USART_ERROR_ARGUMENT; } if (opt->channelmode > 3) { return USART_ERROR_ARGUMENT; } retval = usart_set_baudrate(usart, opt->baudrate, cpuHz); if (retval != USART_OK) { return retval; } if (opt->charlength == 9) { /* charlength set to 9 bits; MODE9 dominates CHRL */ usart->mr |= AVR32_USART_MR_MODE9_MASK; } else { /* CHRL gives the charlength(- 5) when USART_MODE9=0 */ usart->mr |= ((opt->charlength-5)<<AVR32_USART_MR_CHRL_OFFSET); } usart->mr |= (opt->channelmode<<AVR32_USART_MR_CHMODE_OFFSET)| (opt->paritytype<<AVR32_USART_MR_PAR_OFFSET); if (opt->stopbits > 2) { /* set two stop bits */ usart->mr |= (2<<AVR32_USART_MR_NBSTOP_OFFSET); /* and a timeguard period gives the rest */ usart->ttgr = (opt->stopbits-2); } else { /* insert 1, 1.5 or 2 stop bits */ usart->mr |= (opt->stopbits<<AVR32_USART_MR_NBSTOP_OFFSET); } /* enable TX and RX */ usart->cr |= AVR32_USART_CR_TXEN_MASK|AVR32_USART_CR_RXEN_MASK; return USART_OK; } Here is the call graph for this function:

int usart_lwriteLine (  volatile struct avr32_usart_t *  usart, const char *  string )

write one character string to the usart Parameters: usart  base address of the usart string  pointer to an array of chars Returns: status Return values: USART_OK  on success USART_TX_BUSY  on timeout Definition at line 244 of file usart.c. References USART_OK, and usart_putchar(). { int retVal = USART_OK; while (*string != '\0') { retVal = usart_putchar(usart, *string++); if (retVal != USART_OK) { return retVal; } } return USART_OK; } Here is the call graph for this function:

int usart_putchar (  volatile struct avr32_usart_t *  usart, const int  character )

Send a character with the usart. Parameters: usart  base address of the usart character  character to write Returns: status Return values: USART_OK  on success USART_TX_BUSY  on timeout Definition at line 217 of file usart.c. References USART_DEFAULT_TIMEOUT, USART_OK, and USART_TX_BUSY. Referenced by usart_lwriteLine(). { int timeout = USART_DEFAULT_TIMEOUT; do { --timeout; } while ((usart->csr & AVR32_USART_CSR_TXRDY_MASK) == 0 && timeout > 0); if (timeout == 0) { return USART_TX_BUSY; } usart->thr = character; return USART_OK; }

void usart_reset (  volatile struct avr32_usart_t *  usart  )

This function will reset the USART, and disable TX and RX. Parameters: usart  Base address of the usart Definition at line 55 of file usart.c. Referenced by usart_linit(). { /* Disable all usart interrupts, interrupts needed should be set explicitly on every reset */ usart->idr = 0xFFFFffff; /* Reset mode and other registers that could cause unpredictable behaviour after reset */ usart->mr = 0; usart->rtor = 0; usart->ttgr = 0; /* Shutdown RX and TX (will be reenabled when setup is completed successfully), reset status bits and turn off DTR and RTS */ usart->cr = AVR32_USART_CR_RSTRX_MASK| AVR32_USART_CR_RSTTX_MASK| AVR32_USART_CR_RSTSTA_MASK| AVR32_USART_CR_RSTIT_MASK| AVR32_USART_CR_RSTNACK_MASK| AVR32_USART_CR_DTRDIS_MASK| AVR32_USART_CR_RTSDIS_MASK; }

static int usart_set_baudrate (  volatile struct avr32_usart_t *  usart, unsigned int  baudrate, const long  cpuHz )  [static]

This function will calculate a clock divider(CD) and fractional part(FP) that gets the usart as close to a wanted baudrate as possible. Parameters: usart  base address of the usart baudrate  wanted baudrate cpuHz  frequency of the selected clock Returns: status Return values: USART_OK  on success USART_ERROR_ARGUMENT  if wanted baudrate is impossible with given clockspeed Definition at line 93 of file usart.c. References USART_ERROR_ARGUMENT, and USART_OK. Referenced by usart_linit(). { int cd; /* clock divider */ /* * ** BAUDRATE CALCULATION ** * * selected clock selected clock * baudrate = ---------------- or baudrate = ---------------- * 16 x (CD + FP/8) 8 x (CD + FP/8) * * (with 16x oversampling) (with 8x oversampling) */ if (baudrate > (cpuHz/16)) { /* use 8x oversampling */ usart->mr |= (AVR32_USART_MR_OVER_MASK); cd = cpuHz / (8 * baudrate); if (cd < 2) { /* wanted baudrate is too high */ return USART_ERROR_ARGUMENT; } usart->brgr = (cd << AVR32_USART_BRGR_CD_OFFSET); } else { /* use 16x oversampling */ usart->mr &= ~(AVR32_USART_MR_OVER_MASK); cd = cpuHz / (16 * baudrate); if (cd > 65535) { /* wanted baudrate is too low */ return USART_ERROR_ARGUMENT; } usart->brgr = (cd << AVR32_USART_BRGR_CD_OFFSET); } return USART_OK; }

---