Elmicro Computer / Mbed 2 deprecated TestBed-RS485

Example software showing how to use TestBed\'s RS485 feature with mbed\'s hardware UART1. Currently only the setup routine and a \"SendText\" routine are implemented. Can easily be used to develop receiving messages and invoking IRQ handling.

Dependencies:   mbed

main.cpp@0:fe18ab08e05d, 2011-11-21 (annotated)

Committer:
elmicro
Date:
Mon Nov 21 10:29:41 2011 +0000
Revision:
0:fe18ab08e05d
Initial Revision

Who changed what in which revision?

UserRevisionLine numberNew contents of line
elmicro 0:fe18ab08e05d 1 #include "mbed.h"
elmicro 0:fe18ab08e05d 2
elmicro 0:fe18ab08e05d 3 DigitalOut myled(LED1);
elmicro 0:fe18ab08e05d 4 Serial pc(USBTX, USBRX);
elmicro 0:fe18ab08e05d 5
elmicro 0:fe18ab08e05d 6 void RS485_Init(void);
elmicro 0:fe18ab08e05d 7 void RS485_SendChar(unsigned char data);
elmicro 0:fe18ab08e05d 8 void RS485_SendText(char *pString);
elmicro 0:fe18ab08e05d 9
elmicro 0:fe18ab08e05d 10 extern const unsigned int BRLookUp[][3];
elmicro 0:fe18ab08e05d 11
elmicro 0:fe18ab08e05d 12
elmicro 0:fe18ab08e05d 13 void RS485_Init(unsigned int iBR, unsigned int iPCLK)
elmicro 0:fe18ab08e05d 14 {
elmicro 0:fe18ab08e05d 15 /* ===================================================================
elmicro 0:fe18ab08e05d 16 routine: RS485_Init
elmicro 0:fe18ab08e05d 17 purpose: Sets all required parameters for UART1 as RS485
elmicro 0:fe18ab08e05d 18 using following signals:
elmicro 0:fe18ab08e05d 19
elmicro 0:fe18ab08e05d 20 mbed | LPC1768 | function
elmicro 0:fe18ab08e05d 21 -----+---------+---------
elmicro 0:fe18ab08e05d 22 P21 | P2[5] | DTR - '1' for TX
elmicro 0:fe18ab08e05d 23 P25 | P2[1] | RX
elmicro 0:fe18ab08e05d 24 P26 | P2[0] | TX
elmicro 0:fe18ab08e05d 25
elmicro 0:fe18ab08e05d 26 parameters: <iBR> Desired baudrate
elmicro 0:fe18ab08e05d 27 <iPCLK> Current peripheral clock in Hz
elmicro 0:fe18ab08e05d 28 (mbed standard is 24000000)
elmicro 0:fe18ab08e05d 29 date: 2011-11-21
elmicro 0:fe18ab08e05d 30 author: Stefan Guenther | Elektronikladen
elmicro 0:fe18ab08e05d 31 co-author:
elmicro 0:fe18ab08e05d 32 notes: Calculation of baudrate based on NXP's algorithm in
elmicro 0:fe18ab08e05d 33 the LPC17xx manual, Fig. 50 on page 334.
elmicro 0:fe18ab08e05d 34
elmicro 0:fe18ab08e05d 35 PCLK
elmicro 0:fe18ab08e05d 36 baud = ---------------------------------------
elmicro 0:fe18ab08e05d 37 16*(256*DLM+DLL)*(1+(DivAddVal/MulVal))
elmicro 0:fe18ab08e05d 38 -------------------------------------------------------------------*/
elmicro 0:fe18ab08e05d 39
elmicro 0:fe18ab08e05d 40 unsigned int iDL, iFR, iOffset, x;
elmicro 0:fe18ab08e05d 41 unsigned char cDLM, cDLL, cMULVAL, cDIVADDVAL;
elmicro 0:fe18ab08e05d 42
elmicro 0:fe18ab08e05d 43 iDL = iPCLK/(16*iBR);
elmicro 0:fe18ab08e05d 44
elmicro 0:fe18ab08e05d 45 if(iDL*16*iBR==iPCLK) //iDL is an even number
elmicro 0:fe18ab08e05d 46 {
elmicro 0:fe18ab08e05d 47 cDIVADDVAL = 0;
elmicro 0:fe18ab08e05d 48 cMULVAL = 1;
elmicro 0:fe18ab08e05d 49 cDLM = 0;
elmicro 0:fe18ab08e05d 50 cDLL = 0;
elmicro 0:fe18ab08e05d 51 } else //iDL is an odd number
elmicro 0:fe18ab08e05d 52 {
elmicro 0:fe18ab08e05d 53 iOffset=0;
elmicro 0:fe18ab08e05d 54 do //change iFR until it's value is within 1.1 .. 1.9 range
elmicro 0:fe18ab08e05d 55 {
elmicro 0:fe18ab08e05d 56 iOffset+=100;
elmicro 0:fe18ab08e05d 57 iFR = 1005+iOffset;
elmicro 0:fe18ab08e05d 58 iDL=iPCLK/(0.016*iBR*iFR);
elmicro 0:fe18ab08e05d 59 iFR=iPCLK/(0.016*iBR*iDL);
elmicro 0:fe18ab08e05d 60 } while((iFR>1900) || (iFR<1100));
elmicro 0:fe18ab08e05d 61
elmicro 0:fe18ab08e05d 62 //iFR is now correctly calculated!
elmicro 0:fe18ab08e05d 63
elmicro 0:fe18ab08e05d 64 cDLM = (iDL>>8);
elmicro 0:fe18ab08e05d 65 cDLL = iDL;
elmicro 0:fe18ab08e05d 66 x = 0;
elmicro 0:fe18ab08e05d 67
elmicro 0:fe18ab08e05d 68 do //use lookup table to find values for DIVADDVAL and MULVAL
elmicro 0:fe18ab08e05d 69 {
elmicro 0:fe18ab08e05d 70 x++;
elmicro 0:fe18ab08e05d 71 } while(BRLookUp[x][0]<iFR);
elmicro 0:fe18ab08e05d 72
elmicro 0:fe18ab08e05d 73 cDIVADDVAL = BRLookUp[x][1];
elmicro 0:fe18ab08e05d 74 cMULVAL = BRLookUp[x][2];
elmicro 0:fe18ab08e05d 75 }
elmicro 0:fe18ab08e05d 76 //Now, all necessary values are calculated for the desired baudrate according to
elmicro 0:fe18ab08e05d 77 //the current PCLK frequency. These values (cDLM, cDLL, cDIVADDVAL and cMULVAL)
elmicro 0:fe18ab08e05d 78 //now are used to configure UART1 for RS485 communication.
elmicro 0:fe18ab08e05d 79
elmicro 0:fe18ab08e05d 80 LPC_PINCON->PINSEL4 |= 0x80A; //RXD1, TXD1, DTR1
elmicro 0:fe18ab08e05d 81 LPC_SC->PCONP |= (1<<4); //Power on UART1
elmicro 0:fe18ab08e05d 82 //LPC_SC->PCLKSEL //clock default is /4, we keep this
elmicro 0:fe18ab08e05d 83 LPC_UART1->LCR = 0x83; //sets DLAB; 8bit,1stopbit
elmicro 0:fe18ab08e05d 84 LPC_UART1->DLL = cDLL; //UART Divisor Latch LSB
elmicro 0:fe18ab08e05d 85 LPC_UART1->FDR = cDIVADDVAL; //DivAddVal
elmicro 0:fe18ab08e05d 86 LPC_UART1->FDR |= (cMULVAL<<4); //MulVal
elmicro 0:fe18ab08e05d 87 LPC_UART1->DLM = cDLM; //UART Divisor Latch MSB
elmicro 0:fe18ab08e05d 88 LPC_UART1->LCR &=~(1<<7); //clears DLAB
elmicro 0:fe18ab08e05d 89 LPC_UART1->RS485CTRL &=~(1<<1); //Receiver enabled
elmicro 0:fe18ab08e05d 90 LPC_UART1->RS485CTRL &=~(1<<2); //AAD disabled
elmicro 0:fe18ab08e05d 91 LPC_UART1->RS485CTRL |= (1<<3); //DTR used for direction control
elmicro 0:fe18ab08e05d 92 LPC_UART1->RS485CTRL |= (1<<4); //direction control enabled
elmicro 0:fe18ab08e05d 93 LPC_UART1->RS485CTRL |= (1<<5); //DTR=1 when transmitting
elmicro 0:fe18ab08e05d 94 //LPC_UART1->IER |= 1; //RBR IRQ enable
elmicro 0:fe18ab08e05d 95 //LPC_UART1->TER &= ~0x80; //!TXEN - disable transmitter, enable receiver
elmicro 0:fe18ab08e05d 96 //NVIC_EnableIRQ(UART1_IRQn); //set up CM3 NVIC to process UART1 IRQs
elmicro 0:fe18ab08e05d 97 RS485_SendText("\nRS485 communication port setup succesful!\n\n");
elmicro 0:fe18ab08e05d 98 }
elmicro 0:fe18ab08e05d 99
elmicro 0:fe18ab08e05d 100 void RS485_SendChar(unsigned char data)
elmicro 0:fe18ab08e05d 101 {
elmicro 0:fe18ab08e05d 102 LPC_UART1->TER |= 0x80; //enable transmitter
elmicro 0:fe18ab08e05d 103 while (!(LPC_UART1->LSR & 0x20)); //wait for UART1 to be ready - !!could lock up system!!
elmicro 0:fe18ab08e05d 104 LPC_UART1->THR=data; //write to THR register triggers transmission
elmicro 0:fe18ab08e05d 105 }
elmicro 0:fe18ab08e05d 106
elmicro 0:fe18ab08e05d 107 void RS485_SendText(char *pString)
elmicro 0:fe18ab08e05d 108 {
elmicro 0:fe18ab08e05d 109 char *pText; //initialize pointer
elmicro 0:fe18ab08e05d 110 pText=(char *)pString; //set pointer to first character
elmicro 0:fe18ab08e05d 111 while(*pText!=0x00) { //0x00 marks end of text string
elmicro 0:fe18ab08e05d 112 RS485_SendChar(*pText); //send each character seperately
elmicro 0:fe18ab08e05d 113 *pText++; //move pointer to next character
elmicro 0:fe18ab08e05d 114 }
elmicro 0:fe18ab08e05d 115 }
elmicro 0:fe18ab08e05d 116
elmicro 0:fe18ab08e05d 117 int main() {
elmicro 0:fe18ab08e05d 118 RS485_Init(115200, 24000000); //setup RS485 communication with 115200baud
elmicro 0:fe18ab08e05d 119
elmicro 0:fe18ab08e05d 120 while(1) {
elmicro 0:fe18ab08e05d 121 myled = 1;
elmicro 0:fe18ab08e05d 122 wait(0.2);
elmicro 0:fe18ab08e05d 123 myled = 0;
elmicro 0:fe18ab08e05d 124 wait(0.2);
elmicro 0:fe18ab08e05d 125 }
elmicro 0:fe18ab08e05d 126 }
elmicro 0:fe18ab08e05d 127
elmicro 0:fe18ab08e05d 128
elmicro 0:fe18ab08e05d 129 /* ===================================================================
elmicro 0:fe18ab08e05d 130 table: BRLookUp
elmicro 0:fe18ab08e05d 131 purpose: provides settings for UART configuration (baudrate)
elmicro 0:fe18ab08e05d 132 date: 2011-02-04
elmicro 0:fe18ab08e05d 133 author: Stefan Guenther | Elektronikladen
elmicro 0:fe18ab08e05d 134 source: NXP's user manual for the LPC17xx (UM10360), Page 335
elmicro 0:fe18ab08e05d 135 -------------------------------------------------------------------*/
elmicro 0:fe18ab08e05d 136
elmicro 0:fe18ab08e05d 137 const unsigned int BRLookUp[72][3] =
elmicro 0:fe18ab08e05d 138 {
elmicro 0:fe18ab08e05d 139 1000, 0, 1,
elmicro 0:fe18ab08e05d 140 1067, 1, 15,
elmicro 0:fe18ab08e05d 141 1071, 1, 14,
elmicro 0:fe18ab08e05d 142 1077, 1, 13,
elmicro 0:fe18ab08e05d 143 1083, 1, 12,
elmicro 0:fe18ab08e05d 144 1091, 1, 11,
elmicro 0:fe18ab08e05d 145 1100, 1, 9,
elmicro 0:fe18ab08e05d 146 1125, 1, 8,
elmicro 0:fe18ab08e05d 147 1133, 2, 15,
elmicro 0:fe18ab08e05d 148 1143, 1, 7,
elmicro 0:fe18ab08e05d 149 1154, 2, 13,
elmicro 0:fe18ab08e05d 150 1167, 1, 6,
elmicro 0:fe18ab08e05d 151 1182, 2, 11,
elmicro 0:fe18ab08e05d 152 1200, 1, 5,
elmicro 0:fe18ab08e05d 153 1214, 3, 14,
elmicro 0:fe18ab08e05d 154 1222, 2, 9,
elmicro 0:fe18ab08e05d 155 1231, 3, 13,
elmicro 0:fe18ab08e05d 156 1250, 1, 4,
elmicro 0:fe18ab08e05d 157 1267, 4, 15,
elmicro 0:fe18ab08e05d 158 1273, 3, 11,
elmicro 0:fe18ab08e05d 159 1286, 2, 7,
elmicro 0:fe18ab08e05d 160 1300, 3, 10,
elmicro 0:fe18ab08e05d 161 1308, 4, 13,
elmicro 0:fe18ab08e05d 162 1333, 1, 3,
elmicro 0:fe18ab08e05d 163 1357, 5, 14,
elmicro 0:fe18ab08e05d 164 1364, 4, 11,
elmicro 0:fe18ab08e05d 165 1375, 3, 8,
elmicro 0:fe18ab08e05d 166 1385, 5, 13,
elmicro 0:fe18ab08e05d 167 1400, 2, 5,
elmicro 0:fe18ab08e05d 168 1417, 5, 12,
elmicro 0:fe18ab08e05d 169 1429, 3, 7,
elmicro 0:fe18ab08e05d 170 1444, 4, 9,
elmicro 0:fe18ab08e05d 171 1455, 5, 11,
elmicro 0:fe18ab08e05d 172 1462, 6, 13,
elmicro 0:fe18ab08e05d 173 1467, 7, 15,
elmicro 0:fe18ab08e05d 174 1500, 1, 2,
elmicro 0:fe18ab08e05d 175 1533, 8, 15,
elmicro 0:fe18ab08e05d 176 1538, 7, 13,
elmicro 0:fe18ab08e05d 177 1545, 6, 11,
elmicro 0:fe18ab08e05d 178 1556, 5, 9,
elmicro 0:fe18ab08e05d 179 1571, 4, 7,
elmicro 0:fe18ab08e05d 180 1583, 7, 12,
elmicro 0:fe18ab08e05d 181 1600, 3, 5,
elmicro 0:fe18ab08e05d 182 1615, 8, 13,
elmicro 0:fe18ab08e05d 183 1625, 5, 8,
elmicro 0:fe18ab08e05d 184 1636, 7, 11,
elmicro 0:fe18ab08e05d 185 1643, 9, 14,
elmicro 0:fe18ab08e05d 186 1667, 2, 3,
elmicro 0:fe18ab08e05d 187 1692, 9, 13,
elmicro 0:fe18ab08e05d 188 1700, 7, 10,
elmicro 0:fe18ab08e05d 189 1714, 5, 7,
elmicro 0:fe18ab08e05d 190 1727, 8, 11,
elmicro 0:fe18ab08e05d 191 1733, 11, 15,
elmicro 0:fe18ab08e05d 192 1750, 3, 4,
elmicro 0:fe18ab08e05d 193 1769, 10, 13,
elmicro 0:fe18ab08e05d 194 1778, 7, 9,
elmicro 0:fe18ab08e05d 195 1786, 11, 14,
elmicro 0:fe18ab08e05d 196 1800, 4, 5,
elmicro 0:fe18ab08e05d 197 1818, 9, 11,
elmicro 0:fe18ab08e05d 198 1833, 5, 6,
elmicro 0:fe18ab08e05d 199 1846, 11, 13,
elmicro 0:fe18ab08e05d 200 1857, 6, 7,
elmicro 0:fe18ab08e05d 201 1867, 13, 15,
elmicro 0:fe18ab08e05d 202 1875, 7, 8,
elmicro 0:fe18ab08e05d 203 1889, 8, 9,
elmicro 0:fe18ab08e05d 204 1900, 9, 10,
elmicro 0:fe18ab08e05d 205 1909, 10, 11,
elmicro 0:fe18ab08e05d 206 1917, 11, 12,
elmicro 0:fe18ab08e05d 207 1923, 12, 13,
elmicro 0:fe18ab08e05d 208 1929, 13, 14,
elmicro 0:fe18ab08e05d 209 1933, 14, 15
elmicro 0:fe18ab08e05d 210 };