Elmicro Computer
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.
Diff: main.cpp
- Revision:
- 0:fe18ab08e05d
--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/main.cpp Mon Nov 21 10:29:41 2011 +0000
@@ -0,0 +1,210 @@
+#include "mbed.h"
+
+DigitalOut myled(LED1);
+Serial pc(USBTX, USBRX);
+
+void RS485_Init(void);
+void RS485_SendChar(unsigned char data);
+void RS485_SendText(char *pString);
+
+extern const unsigned int BRLookUp[][3];
+
+
+void RS485_Init(unsigned int iBR, unsigned int iPCLK)
+{
+/* ===================================================================
+ routine: RS485_Init
+ purpose: Sets all required parameters for UART1 as RS485
+ using following signals:
+
+ mbed | LPC1768 | function
+ -----+---------+---------
+ P21 | P2[5] | DTR - '1' for TX
+ P25 | P2[1] | RX
+ P26 | P2[0] | TX
+
+ parameters: <iBR> Desired baudrate
+ <iPCLK> Current peripheral clock in Hz
+ (mbed standard is 24000000)
+ date: 2011-11-21
+ author: Stefan Guenther | Elektronikladen
+ co-author:
+ notes: Calculation of baudrate based on NXP's algorithm in
+ the LPC17xx manual, Fig. 50 on page 334.
+
+ PCLK
+ baud = ---------------------------------------
+ 16*(256*DLM+DLL)*(1+(DivAddVal/MulVal))
+ -------------------------------------------------------------------*/
+
+ unsigned int iDL, iFR, iOffset, x;
+ unsigned char cDLM, cDLL, cMULVAL, cDIVADDVAL;
+
+ iDL = iPCLK/(16*iBR);
+
+ if(iDL*16*iBR==iPCLK) //iDL is an even number
+ {
+ cDIVADDVAL = 0;
+ cMULVAL = 1;
+ cDLM = 0;
+ cDLL = 0;
+ } else //iDL is an odd number
+ {
+ iOffset=0;
+ do //change iFR until it's value is within 1.1 .. 1.9 range
+ {
+ iOffset+=100;
+ iFR = 1005+iOffset;
+ iDL=iPCLK/(0.016*iBR*iFR);
+ iFR=iPCLK/(0.016*iBR*iDL);
+ } while((iFR>1900) || (iFR<1100));
+
+ //iFR is now correctly calculated!
+
+ cDLM = (iDL>>8);
+ cDLL = iDL;
+ x = 0;
+
+ do //use lookup table to find values for DIVADDVAL and MULVAL
+ {
+ x++;
+ } while(BRLookUp[x][0]<iFR);
+
+ cDIVADDVAL = BRLookUp[x][1];
+ cMULVAL = BRLookUp[x][2];
+ }
+ //Now, all necessary values are calculated for the desired baudrate according to
+ //the current PCLK frequency. These values (cDLM, cDLL, cDIVADDVAL and cMULVAL)
+ //now are used to configure UART1 for RS485 communication.
+
+ LPC_PINCON->PINSEL4 |= 0x80A; //RXD1, TXD1, DTR1
+ LPC_SC->PCONP |= (1<<4); //Power on UART1
+ //LPC_SC->PCLKSEL //clock default is /4, we keep this
+ LPC_UART1->LCR = 0x83; //sets DLAB; 8bit,1stopbit
+ LPC_UART1->DLL = cDLL; //UART Divisor Latch LSB
+ LPC_UART1->FDR = cDIVADDVAL; //DivAddVal
+ LPC_UART1->FDR |= (cMULVAL<<4); //MulVal
+ LPC_UART1->DLM = cDLM; //UART Divisor Latch MSB
+ LPC_UART1->LCR &=~(1<<7); //clears DLAB
+ LPC_UART1->RS485CTRL &=~(1<<1); //Receiver enabled
+ LPC_UART1->RS485CTRL &=~(1<<2); //AAD disabled
+ LPC_UART1->RS485CTRL |= (1<<3); //DTR used for direction control
+ LPC_UART1->RS485CTRL |= (1<<4); //direction control enabled
+ LPC_UART1->RS485CTRL |= (1<<5); //DTR=1 when transmitting
+ //LPC_UART1->IER |= 1; //RBR IRQ enable
+ //LPC_UART1->TER &= ~0x80; //!TXEN - disable transmitter, enable receiver
+ //NVIC_EnableIRQ(UART1_IRQn); //set up CM3 NVIC to process UART1 IRQs
+ RS485_SendText("\nRS485 communication port setup succesful!\n\n");
+}
+
+void RS485_SendChar(unsigned char data)
+{
+ LPC_UART1->TER |= 0x80; //enable transmitter
+ while (!(LPC_UART1->LSR & 0x20)); //wait for UART1 to be ready - !!could lock up system!!
+ LPC_UART1->THR=data; //write to THR register triggers transmission
+}
+
+void RS485_SendText(char *pString)
+{
+ char *pText; //initialize pointer
+ pText=(char *)pString; //set pointer to first character
+ while(*pText!=0x00) { //0x00 marks end of text string
+ RS485_SendChar(*pText); //send each character seperately
+ *pText++; //move pointer to next character
+ }
+}
+
+int main() {
+ RS485_Init(115200, 24000000); //setup RS485 communication with 115200baud
+
+ while(1) {
+ myled = 1;
+ wait(0.2);
+ myled = 0;
+ wait(0.2);
+ }
+}
+
+
+/* ===================================================================
+ table: BRLookUp
+ purpose: provides settings for UART configuration (baudrate)
+ date: 2011-02-04
+ author: Stefan Guenther | Elektronikladen
+ source: NXP's user manual for the LPC17xx (UM10360), Page 335
+ -------------------------------------------------------------------*/
+
+const unsigned int BRLookUp[72][3] =
+{
+ 1000, 0, 1,
+ 1067, 1, 15,
+ 1071, 1, 14,
+ 1077, 1, 13,
+ 1083, 1, 12,
+ 1091, 1, 11,
+ 1100, 1, 9,
+ 1125, 1, 8,
+ 1133, 2, 15,
+ 1143, 1, 7,
+ 1154, 2, 13,
+ 1167, 1, 6,
+ 1182, 2, 11,
+ 1200, 1, 5,
+ 1214, 3, 14,
+ 1222, 2, 9,
+ 1231, 3, 13,
+ 1250, 1, 4,
+ 1267, 4, 15,
+ 1273, 3, 11,
+ 1286, 2, 7,
+ 1300, 3, 10,
+ 1308, 4, 13,
+ 1333, 1, 3,
+ 1357, 5, 14,
+ 1364, 4, 11,
+ 1375, 3, 8,
+ 1385, 5, 13,
+ 1400, 2, 5,
+ 1417, 5, 12,
+ 1429, 3, 7,
+ 1444, 4, 9,
+ 1455, 5, 11,
+ 1462, 6, 13,
+ 1467, 7, 15,
+ 1500, 1, 2,
+ 1533, 8, 15,
+ 1538, 7, 13,
+ 1545, 6, 11,
+ 1556, 5, 9,
+ 1571, 4, 7,
+ 1583, 7, 12,
+ 1600, 3, 5,
+ 1615, 8, 13,
+ 1625, 5, 8,
+ 1636, 7, 11,
+ 1643, 9, 14,
+ 1667, 2, 3,
+ 1692, 9, 13,
+ 1700, 7, 10,
+ 1714, 5, 7,
+ 1727, 8, 11,
+ 1733, 11, 15,
+ 1750, 3, 4,
+ 1769, 10, 13,
+ 1778, 7, 9,
+ 1786, 11, 14,
+ 1800, 4, 5,
+ 1818, 9, 11,
+ 1833, 5, 6,
+ 1846, 11, 13,
+ 1857, 6, 7,
+ 1867, 13, 15,
+ 1875, 7, 8,
+ 1889, 8, 9,
+ 1900, 9, 10,
+ 1909, 10, 11,
+ 1917, 11, 12,
+ 1923, 12, 13,
+ 1929, 13, 14,
+ 1933, 14, 15
+};