/************************************************************************** * * Copyright (C) 2007 Steve Karg * RS-485 initialization on AT91SAM7S inspired by Keil Eletronik serial.c * * Permission is hereby granted, free of charge, to any person obtaining * a copy of this software and associated documentation files (the * "Software"), to deal in the Software without restriction, including * without limitation the rights to use, copy, modify, merge, publish, * distribute, sublicense, and/or sell copies of the Software, and to * permit persons to whom the Software is furnished to do so, subject to * the following conditions: * * The above copyright notice and this permission notice shall be included * in all copies or substantial portions of the Software. * * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. * IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY * CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, * TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE * SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE. * *********************************************************************/ /* The module handles sending data out the RS-485 port */ /* and handles receiving data from the RS-485 port. */ /* Customize this file for your specific hardware */ #include #include #include #include #include #include "timer.h" /* This file has been customized for use with UART0 on the AT91SAM7S-EK */ #include "board.h" /* UART */ static volatile AT91S_USART *RS485_Interface = AT91C_BASE_US0; /* baud rate */ static int RS485_Baud = 38400; /* The minimum time after the end of the stop bit of the final octet of a */ /* received frame before a node may enable its EIA-485 driver: 40 bit times. */ /* At 9600 baud, 40 bit times would be about 4.166 milliseconds */ /* At 19200 baud, 40 bit times would be about 2.083 milliseconds */ /* At 38400 baud, 40 bit times would be about 1.041 milliseconds */ /* At 57600 baud, 40 bit times would be about 0.694 milliseconds */ /* At 76800 baud, 40 bit times would be about 0.520 milliseconds */ /* At 115200 baud, 40 bit times would be about 0.347 milliseconds */ /* 40 bits is 4 octets including a start and stop bit with each octet */ #define Tturnaround (40UL) /* turnaround_time_milliseconds = (Tturnaround*1000UL)/RS485_Baud; */ /**************************************************************************** * DESCRIPTION: Initializes the RS485 hardware and variables, and starts in * receive mode. * RETURN: none * ALGORITHM: none * NOTES: none *****************************************************************************/ void RS485_Initialize( void) { /* Enable the USART0 clock in the Power Management Controller */ volatile AT91PS_PMC pPMC = AT91C_BASE_PMC; pPMC->PMC_PCER = pPMC->PMC_PCSR | (1 << AT91C_ID_US0); /* Disable and clear USART0 interrupt in AIC Interrupt Disable Command Register */ volatile AT91PS_AIC pAIC = AT91C_BASE_AIC; pAIC->AIC_IDCR = (1 << AT91C_ID_US0); pAIC->AIC_ICCR = (1 << AT91C_ID_US0); /* enable the peripheral by disabling the pin in the PIO controller */ *AT91C_PIOA_PDR = AT91C_PA5_RXD0 | AT91C_PA6_TXD0 | AT91C_PA7_RTS0; RS485_Interface->US_CR = AT91C_US_RSTRX | /* Reset Receiver */ AT91C_US_RSTTX | /* Reset Transmitter */ AT91C_US_RSTSTA | /* Clear status register */ AT91C_US_RXDIS | /* Receiver Disable */ AT91C_US_TXDIS; /* Transmitter Disable */ RS485_Interface->US_MR = AT91C_US_USMODE_RS485 | /* RS-485 Mode - RTS auto assert */ AT91C_US_CLKS_CLOCK | /* Clock = MCK */ AT91C_US_CHRL_8_BITS | /* 8-bit Data */ AT91C_US_PAR_NONE | /* No Parity */ AT91C_US_NBSTOP_1_BIT; /* 1 Stop Bit */ /* set the Time Guard to release RTS after x bit times */ RS485_Interface->US_TTGR = 1; /* Receiver Time-out disabled */ RS485_Interface->US_RTOR = 0; /* baud rate */ RS485_Interface->US_BRGR = MCK / 16 / RS485_Baud; RS485_Interface->US_CR = AT91C_US_RXEN | /* Receiver Enable */ AT91C_US_TXEN; /* Transmitter Enable */ return; } void RS485_Cleanup( void) { } /**************************************************************************** * DESCRIPTION: Returns the baud rate that we are currently running at * RETURN: none * ALGORITHM: none * NOTES: none *****************************************************************************/ uint32_t RS485_Get_Baud_Rate( void) { return RS485_Baud; } /**************************************************************************** * DESCRIPTION: Sets the baud rate for the chip USART * RETURN: none * ALGORITHM: none * NOTES: none *****************************************************************************/ bool RS485_Set_Baud_Rate( uint32_t baud) { bool valid = true; switch (baud) { case 9600: case 19200: case 38400: case 57600: case 76800: case 115200: RS485_Baud = baud; RS485_Interface->US_BRGR = MCK / 16 / baud; /* FIXME: store the baud rate */ break; default: valid = false; break; } return valid; } /**************************************************************************** * DESCRIPTION: Waits on the SilenceTimer for 40 bits. * RETURN: none * ALGORITHM: none * NOTES: none *****************************************************************************/ void RS485_Turnaround_Delay( void) { uint16_t turnaround_time; /* delay after reception before trasmitting - per MS/TP spec */ /* wait a minimum 40 bit times since reception */ /* at least 1 ms for errors: rounding, clock tick */ turnaround_time = 2 + ((Tturnaround * 1000UL) / RS485_Baud); while (Timer_Silence() < turnaround_time) { /* do nothing - wait for timer to increment */ }; } /**************************************************************************** * DESCRIPTION: Enable or disable the transmitter * RETURN: none * ALGORITHM: none * NOTES: The Atmel ARM7 has an automatic enable/disable in RS485 mode. *****************************************************************************/ void RS485_Transmitter_Enable( bool enable) { (void) enable; } /**************************************************************************** * DESCRIPTION: Send some data and wait until it is sent * RETURN: none * ALGORITHM: none * NOTES: none *****************************************************************************/ void RS485_Send_Data( uint8_t * buffer, /* data to send */ uint16_t nbytes) { /* number of bytes of data */ /* LED on send */ volatile AT91PS_PIO pPIO = AT91C_BASE_PIOA; /* LED ON */ pPIO->PIO_CODR = LED1; /* send all the bytes */ while (nbytes) { while (!(RS485_Interface->US_CSR & AT91C_US_TXRDY)) { /* do nothing - wait until Tx buffer is empty */ } RS485_Interface->US_THR = *buffer; buffer++; nbytes--; } while (!(RS485_Interface->US_CSR & AT91C_US_TXRDY)) { /* do nothing - wait until Tx buffer is empty */ } /* per MSTP spec */ Timer_Silence_Reset(); } /**************************************************************************** * DESCRIPTION: Return true if a framing or overrun error is present * RETURN: true if error * ALGORITHM: none * NOTES: Clears any error flags. *****************************************************************************/ bool RS485_ReceiveError( void) { bool ReceiveError = false; /* LED on send */ volatile AT91PS_PIO pPIO = AT91C_BASE_PIOA; /* check for data or error */ if (RS485_Interface->US_CSR & (AT91C_US_OVRE | AT91C_US_FRAME)) { /* clear the error flag */ RS485_Interface->US_CR = AT91C_US_RSTSTA; ReceiveError = true; /* LED ON */ pPIO->PIO_CODR = LED2; } return ReceiveError; } /**************************************************************************** * DESCRIPTION: Return true if data is available * RETURN: true if data is available, with the data in the parameter set * ALGORITHM: none * NOTES: none *****************************************************************************/ bool RS485_DataAvailable( uint8_t * DataRegister) { bool DataAvailable = false; /* LED on send */ volatile AT91PS_PIO pPIO = AT91C_BASE_PIOA; if (RS485_Interface->US_CSR & AT91C_US_RXRDY) { /* data is available */ if (DataRegister) { *DataRegister = RS485_Interface->US_RHR; } DataAvailable = true; /* LED ON */ pPIO->PIO_CODR = LED2; } return DataAvailable; } #ifdef TEST_RS485 int main( void) { unsigned i = 0; uint8_t DataRegister; RS485_Set_Baud_Rate(38400); RS485_Initialize(); /* receive task */ for (;;) { if (RS485_ReceiveError()) { fprintf(stderr, "ERROR "); } else if (RS485_DataAvailable(&DataRegister)) { fprintf(stderr, "%02X ", DataRegister); } } } #endif