Adhithya Rajasekaran / MODSERIAL

Bug fix release

Dependents:   esp8266test

Fork of MODSERIAL by Andy K

example_dma.cpp@9:b3cdae80e7a9, 2010-11-23 (annotated)

Committer:
AjK
Date:
Tue Nov 23 21:34:54 2010 +0000
Revision:
9:b3cdae80e7a9
Child:
11:a93a62eeeb9d
1.9

Who changed what in which revision?

UserRevisionLine numberNew contents of line
AjK 9:b3cdae80e7a9 1 #ifdef COMPILE_EXAMPLE_CODE_MODSERIAL_MODDMA
AjK 9:b3cdae80e7a9 2
AjK 9:b3cdae80e7a9 3 /*
AjK 9:b3cdae80e7a9 4 * To run this test program, link p9 to p10 so the Serial loops
AjK 9:b3cdae80e7a9 5 * back and receives characters it sends.
AjK 9:b3cdae80e7a9 6 */
AjK 9:b3cdae80e7a9 7
AjK 9:b3cdae80e7a9 8 #include "mbed.h"
AjK 9:b3cdae80e7a9 9
AjK 9:b3cdae80e7a9 10 /* Note, this example requires that you also import into the Mbed
AjK 9:b3cdae80e7a9 11 compiler the MODDMA project as well as MODSERIAL
AjK 9:b3cdae80e7a9 12 http://mbed.org/users/AjK/libraries/MODDMA/latest
AjK 9:b3cdae80e7a9 13 MODDMA.h MUST come before MODSERIAL.h */
AjK 9:b3cdae80e7a9 14 #include "MODDMA.h" // <--- Declare first
AjK 9:b3cdae80e7a9 15 #include "MODSERIAL.h" // Flollowed by MODSERIAL
AjK 9:b3cdae80e7a9 16
AjK 9:b3cdae80e7a9 17 DigitalOut led1(LED1);
AjK 9:b3cdae80e7a9 18 DigitalOut led2(LED2);
AjK 9:b3cdae80e7a9 19 DigitalOut led3(LED3);
AjK 9:b3cdae80e7a9 20 DigitalOut led4(LED4);
AjK 9:b3cdae80e7a9 21
AjK 9:b3cdae80e7a9 22 MODSERIAL pc(USBTX, USBRX);
AjK 9:b3cdae80e7a9 23
AjK 9:b3cdae80e7a9 24 /*
AjK 9:b3cdae80e7a9 25 * As experiement, you can define MODSERIAL as show here and see what
AjK 9:b3cdae80e7a9 26 * effects it has on the LEDs.
AjK 9:b3cdae80e7a9 27 *
AjK 9:b3cdae80e7a9 28 * MODSERIAL uart(TX_PIN, RX_PIN, 512);
AjK 9:b3cdae80e7a9 29 * With this, the 512 characters sent can straight into the buffer
AjK 9:b3cdae80e7a9 30 * vary quickly. This means LED1 is only on briefly as the TX buffer
AjK 9:b3cdae80e7a9 31 * fills.
AjK 9:b3cdae80e7a9 32 *
AjK 9:b3cdae80e7a9 33 * MODSERIAL uart(TX_PIN, RX_PIN, 32);
AjK 9:b3cdae80e7a9 34 * With this, the buffer is smaller than the default 256 bytes and
AjK 9:b3cdae80e7a9 35 * therefore LED1 stays on much longer while the system waits for
AjK 9:b3cdae80e7a9 36 * room in the TX buffer.
AjK 9:b3cdae80e7a9 37 */
AjK 9:b3cdae80e7a9 38 MODSERIAL uart(TX_PIN, RX_PIN);
AjK 9:b3cdae80e7a9 39
AjK 9:b3cdae80e7a9 40 MODDMA dma;
AjK 9:b3cdae80e7a9 41
AjK 9:b3cdae80e7a9 42 // This function is called when a character goes from the TX buffer
AjK 9:b3cdae80e7a9 43 // to the Uart THR FIFO register.
AjK 9:b3cdae80e7a9 44 void txCallback(void) {
AjK 9:b3cdae80e7a9 45 led2 = !led2;
AjK 9:b3cdae80e7a9 46 }
AjK 9:b3cdae80e7a9 47
AjK 9:b3cdae80e7a9 48 // This function is called when TX buffer goes empty
AjK 9:b3cdae80e7a9 49 void txEmpty(void) {
AjK 9:b3cdae80e7a9 50 led2 = 0;
AjK 9:b3cdae80e7a9 51 pc.puts(" Done. ");
AjK 9:b3cdae80e7a9 52 }
AjK 9:b3cdae80e7a9 53
AjK 9:b3cdae80e7a9 54 void dmaComplete(void) {
AjK 9:b3cdae80e7a9 55 led1 = 1;
AjK 9:b3cdae80e7a9 56 }
AjK 9:b3cdae80e7a9 57
AjK 9:b3cdae80e7a9 58 // This function is called when a character goes into the RX buffer.
AjK 9:b3cdae80e7a9 59 void rxCallback(void) {
AjK 9:b3cdae80e7a9 60 led3 = !led3;
AjK 9:b3cdae80e7a9 61 pc.putc(uart.getc());
AjK 9:b3cdae80e7a9 62 }
AjK 9:b3cdae80e7a9 63
AjK 9:b3cdae80e7a9 64 int main() {
AjK 9:b3cdae80e7a9 65 char s1[] = " *DMA* *DMA* *DMA* *DMA* *DMA* *DMA* *DMA* ";
AjK 9:b3cdae80e7a9 66 int c = 'A';
AjK 9:b3cdae80e7a9 67
AjK 9:b3cdae80e7a9 68 // Tell MODSERIAL where the MODDMA controller is.
AjK 9:b3cdae80e7a9 69 pc.MODDMA( &dma );
AjK 9:b3cdae80e7a9 70
AjK 9:b3cdae80e7a9 71 // Ensure the baud rate for the PC "USB" serial is much
AjK 9:b3cdae80e7a9 72 // higher than "uart" baud rate below.
AjK 9:b3cdae80e7a9 73 pc.baud( PC_BAUD );
AjK 9:b3cdae80e7a9 74
AjK 9:b3cdae80e7a9 75 // Use a deliberatly slow baud to fill up the TX buffer
AjK 9:b3cdae80e7a9 76 uart.baud(1200);
AjK 9:b3cdae80e7a9 77
AjK 9:b3cdae80e7a9 78 uart.attach( &txCallback, MODSERIAL::TxIrq );
AjK 9:b3cdae80e7a9 79 uart.attach( &rxCallback, MODSERIAL::RxIrq );
AjK 9:b3cdae80e7a9 80 uart.attach( &txEmpty, MODSERIAL::TxEmpty );
AjK 9:b3cdae80e7a9 81
AjK 9:b3cdae80e7a9 82 // Loop sending characters. We send 512
AjK 9:b3cdae80e7a9 83 // which is twice the default TX/RX buffer size.
AjK 9:b3cdae80e7a9 84
AjK 9:b3cdae80e7a9 85 led1 = 0;
AjK 9:b3cdae80e7a9 86
AjK 9:b3cdae80e7a9 87 // Send the buffer s using DMA channel 7
AjK 9:b3cdae80e7a9 88 pc.attach_dma_complete( &dmaComplete );
AjK 9:b3cdae80e7a9 89 pc.dmaSend( s1, sizeof(s1), MODDMA::Channel_7 );
AjK 9:b3cdae80e7a9 90
AjK 9:b3cdae80e7a9 91 for (int loop = 0; loop < 512; loop++) {
AjK 9:b3cdae80e7a9 92 uart.printf("%c", c);
AjK 9:b3cdae80e7a9 93 c++;
AjK 9:b3cdae80e7a9 94 if (c > 'Z') c = 'A';
AjK 9:b3cdae80e7a9 95 }
AjK 9:b3cdae80e7a9 96
AjK 9:b3cdae80e7a9 97 led1 = 0; // Show the end of sending by switching off LED1.
AjK 9:b3cdae80e7a9 98
AjK 9:b3cdae80e7a9 99 // End program. Flash LED4. Notice how LED 2 and 3 continue
AjK 9:b3cdae80e7a9 100 // to flash for a short period while the interrupt system
AjK 9:b3cdae80e7a9 101 // continues to send the characters left in the TX buffer.
AjK 9:b3cdae80e7a9 102
AjK 9:b3cdae80e7a9 103 while(1) {
AjK 9:b3cdae80e7a9 104 led4 = !led4;
AjK 9:b3cdae80e7a9 105 wait(0.25);
AjK 9:b3cdae80e7a9 106 }
AjK 9:b3cdae80e7a9 107 }
AjK 9:b3cdae80e7a9 108
AjK 9:b3cdae80e7a9 109 /*
AjK 9:b3cdae80e7a9 110 * Notes. Here is the sort of output you can expect on your PC/Mac/Linux host
AjK 9:b3cdae80e7a9 111 * machine that is connected to the "pc" USB serial port.
AjK 9:b3cdae80e7a9 112 *
AjK 9:b3cdae80e7a9 113 * *DMA* *DMA* *DMA* *DMA* *DMA* *DMA* *DMA* ABCDEFGHIJKLMNOPQRSTUVWXYZABCDE
AjK 9:b3cdae80e7a9 114 * FGHIJKLMNOPQRSTUVWXYZABCDEFGHIJKLMNOPQRSTUVWXYZABCDEFGHIJKLMNOPQRSTUVWXYZA
AjK 9:b3cdae80e7a9 115 * BCDEFGHIJKLMNOPQRSTUVWXYZABCDEFGHIJKLMNOPQRSTUVWXYZABCDEFGHIJKLMNOPQRSTUVW
AjK 9:b3cdae80e7a9 116 * XYZABCDEFGHIJKLMNOPQRSTUVWXYZABCDEFGHIJKLMNOPQRSTUVWXYZABCDEFGHIJKLMNOPQRS
AjK 9:b3cdae80e7a9 117 * TUVWXYZABCDEFGHIJKLMNOPQRSTUVWXYZABCDEFGHIJKLMNOPQRSTUVWXYZABCDEFGHIJKLMNO
AjK 9:b3cdae80e7a9 118 * PQRSTUVWXYZABCDEFGHIJKLMNOPQRSTUVWXYZABCDEFGHIJKLMNOPQRSTUVWXYZABCDEFGHIJK
AjK 9:b3cdae80e7a9 119 * LMNOPQRSTUVWXYZABCDEFGHIJKLMNOPQRSTUVWXYZABCDEFGHIJKLMNOPQRSTUVWXYZABCDEFG
AjK 9:b3cdae80e7a9 120 * HIJKLMNOPQRSTUVWXYZABCDEFGHIJKLMNOPQ Done. R
AjK 9:b3cdae80e7a9 121 *
AjK 9:b3cdae80e7a9 122 * Note how the DMA blocks the TX buffer sending under standard interrupt control.
AjK 9:b3cdae80e7a9 123 * Not until the DMA transfer is complete will "normal" buffered TX sending resume.
AjK 9:b3cdae80e7a9 124 *
AjK 9:b3cdae80e7a9 125 * Of interest is that last "R" character after the system has said "Done."
AjK 9:b3cdae80e7a9 126 * This comes from the fact that the TxEmpty callback is made when the TX buffer
AjK 9:b3cdae80e7a9 127 * becomes empty. MODSERIAL makes use of the fact that the Uarts built into the
AjK 9:b3cdae80e7a9 128 * LPC17xx device use a 16 byte FIFO on both RX and TX channels. This means that
AjK 9:b3cdae80e7a9 129 * when the TxEmpty callback is made, the TX buffer is empty, but that just means
AjK 9:b3cdae80e7a9 130 * the "last few characters" were written to the TX FIFO. So although the TX
AjK 9:b3cdae80e7a9 131 * buffer has gone empty, the Uart's transmit system is still sending any remaining
AjK 9:b3cdae80e7a9 132 * characters from it's TX FIFO. If you want to be truely sure all the characters
AjK 9:b3cdae80e7a9 133 * you have sent have left the Mbed then call txIsBusy(); This function will
AjK 9:b3cdae80e7a9 134 * return true if characters are still being sent. If it returns false after
AjK 9:b3cdae80e7a9 135 * the Tx buffer is empty then all your characters have been sent.
AjK 9:b3cdae80e7a9 136 *
AjK 9:b3cdae80e7a9 137 * In a similar way, when characters are received into the RX FIFO, the entire
AjK 9:b3cdae80e7a9 138 * FIFO contents is moved to the RX buffer, assuming there is room left in the
AjK 9:b3cdae80e7a9 139 * RX buffer. If there is not, any remaining characters are left in the RX FIFO
AjK 9:b3cdae80e7a9 140 * and will be moved to the RX buffer on the next interrupt or when the running
AjK 9:b3cdae80e7a9 141 * program removes a character(s) from the RX buffer with the getc() method.
AjK 9:b3cdae80e7a9 142 */
AjK 9:b3cdae80e7a9 143
AjK 9:b3cdae80e7a9 144 #endif