Amanda Travieso / MODSERIAL

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Fork of MODSERIAL by Andy K

example_dma.cpp@12:8c7394e2ae7f, 2011-01-20 (annotated)

Committer:
AjK
Date:
Thu Jan 20 11:57:32 2011 +0000
Revision:
12:8c7394e2ae7f
Parent:
11:a93a62eeeb9d 
1.12 See ChangeLog

Who changed what in which revision?

UserRevisionLine numberNew contents of line
AjK 12:8c7394e2ae7f 1 #ifdef COMPILE_EXAMPLE_CODE_MODSERIAL_MODDMA
AjK 12:8c7394e2ae7f 2
AjK 12:8c7394e2ae7f 3 /*
AjK 12:8c7394e2ae7f 4 * To run this test program, link p9 to p10 so the Serial loops
AjK 12:8c7394e2ae7f 5 * back and receives characters it sends.
AjK 12:8c7394e2ae7f 6 */
AjK 12:8c7394e2ae7f 7
AjK 12:8c7394e2ae7f 8 #include "mbed.h"
AjK 12:8c7394e2ae7f 9
AjK 12:8c7394e2ae7f 10 /* Note, this example requires that you also import into the Mbed
AjK 12:8c7394e2ae7f 11 compiler the MODDMA project as well as MODSERIAL
AjK 12:8c7394e2ae7f 12 http://mbed.org/users/AjK/libraries/MODDMA/latest
AjK 12:8c7394e2ae7f 13 MODDMA.h MUST come before MODSERIAL.h */
AjK 12:8c7394e2ae7f 14 #include "MODDMA.h" // <--- Declare first
AjK 12:8c7394e2ae7f 15 #include "MODSERIAL.h" // Flollowed by MODSERIAL
AjK 12:8c7394e2ae7f 16
AjK 12:8c7394e2ae7f 17 DigitalOut led1(LED1);
AjK 12:8c7394e2ae7f 18 DigitalOut led2(LED2);
AjK 12:8c7394e2ae7f 19 DigitalOut led3(LED3);
AjK 12:8c7394e2ae7f 20 DigitalOut led4(LED4);
AjK 12:8c7394e2ae7f 21
AjK 12:8c7394e2ae7f 22 MODSERIAL pc(USBTX, USBRX);
AjK 12:8c7394e2ae7f 23
AjK 12:8c7394e2ae7f 24 /*
AjK 12:8c7394e2ae7f 25 * As experiement, you can define MODSERIAL as show here and see what
AjK 12:8c7394e2ae7f 26 * effects it has on the LEDs.
AjK 12:8c7394e2ae7f 27 *
AjK 12:8c7394e2ae7f 28 * MODSERIAL uart(TX_PIN, RX_PIN, 512);
AjK 12:8c7394e2ae7f 29 * With this, the 512 characters sent can straight into the buffer
AjK 12:8c7394e2ae7f 30 * vary quickly. This means LED1 is only on briefly as the TX buffer
AjK 12:8c7394e2ae7f 31 * fills.
AjK 12:8c7394e2ae7f 32 *
AjK 12:8c7394e2ae7f 33 * MODSERIAL uart(TX_PIN, RX_PIN, 32);
AjK 12:8c7394e2ae7f 34 * With this, the buffer is smaller than the default 256 bytes and
AjK 12:8c7394e2ae7f 35 * therefore LED1 stays on much longer while the system waits for
AjK 12:8c7394e2ae7f 36 * room in the TX buffer.
AjK 12:8c7394e2ae7f 37 */
AjK 12:8c7394e2ae7f 38 MODSERIAL uart(TX_PIN, RX_PIN);
AjK 12:8c7394e2ae7f 39
AjK 12:8c7394e2ae7f 40 MODDMA dma;
AjK 12:8c7394e2ae7f 41
AjK 12:8c7394e2ae7f 42 // This function is called when a character goes from the TX buffer
AjK 12:8c7394e2ae7f 43 // to the Uart THR FIFO register.
AjK 12:8c7394e2ae7f 44 void txCallback(void) {
AjK 12:8c7394e2ae7f 45 led2 = !led2;
AjK 12:8c7394e2ae7f 46 }
AjK 12:8c7394e2ae7f 47
AjK 12:8c7394e2ae7f 48 // This function is called when TX buffer goes empty
AjK 12:8c7394e2ae7f 49 void txEmpty(void) {
AjK 12:8c7394e2ae7f 50 led2 = 0;
AjK 12:8c7394e2ae7f 51 pc.puts(" Done. ");
AjK 12:8c7394e2ae7f 52 }
AjK 12:8c7394e2ae7f 53
AjK 12:8c7394e2ae7f 54 void dmaComplete(void) {
AjK 12:8c7394e2ae7f 55 led1 = 1;
AjK 12:8c7394e2ae7f 56 }
AjK 12:8c7394e2ae7f 57
AjK 12:8c7394e2ae7f 58 // This function is called when a character goes into the RX buffer.
AjK 12:8c7394e2ae7f 59 void rxCallback(void) {
AjK 12:8c7394e2ae7f 60 led3 = !led3;
AjK 12:8c7394e2ae7f 61 pc.putc(uart.getc());
AjK 12:8c7394e2ae7f 62 }
AjK 12:8c7394e2ae7f 63
AjK 12:8c7394e2ae7f 64 int main() {
AjK 12:8c7394e2ae7f 65 char s1[] = " *DMA* *DMA* *DMA* *DMA* *DMA* *DMA* *DMA* ";
AjK 12:8c7394e2ae7f 66 int c = 'A';
AjK 12:8c7394e2ae7f 67
AjK 12:8c7394e2ae7f 68 // Tell MODSERIAL where the MODDMA controller is.
AjK 12:8c7394e2ae7f 69 pc.MODDMA( &dma );
AjK 12:8c7394e2ae7f 70
AjK 12:8c7394e2ae7f 71 // Ensure the baud rate for the PC "USB" serial is much
AjK 12:8c7394e2ae7f 72 // higher than "uart" baud rate below.
AjK 12:8c7394e2ae7f 73 pc.baud( PC_BAUD );
AjK 12:8c7394e2ae7f 74
AjK 12:8c7394e2ae7f 75 // Use a deliberatly slow baud to fill up the TX buffer
AjK 12:8c7394e2ae7f 76 uart.baud(1200);
AjK 12:8c7394e2ae7f 77
AjK 12:8c7394e2ae7f 78 uart.attach( &txCallback, MODSERIAL::TxIrq );
AjK 12:8c7394e2ae7f 79 uart.attach( &rxCallback, MODSERIAL::RxIrq );
AjK 12:8c7394e2ae7f 80 uart.attach( &txEmpty, MODSERIAL::TxEmpty );
AjK 12:8c7394e2ae7f 81
AjK 12:8c7394e2ae7f 82 // Loop sending characters. We send 512
AjK 12:8c7394e2ae7f 83 // which is twice the default TX/RX buffer size.
AjK 12:8c7394e2ae7f 84
AjK 12:8c7394e2ae7f 85 led1 = 0;
AjK 12:8c7394e2ae7f 86
AjK 12:8c7394e2ae7f 87 // Send the buffer s using DMA channel 7
AjK 12:8c7394e2ae7f 88 pc.attach_dmaSendComplete( &dmaComplete );
AjK 12:8c7394e2ae7f 89 pc.dmaSend( s1, sizeof(s1), MODDMA::Channel_7 );
AjK 12:8c7394e2ae7f 90
AjK 12:8c7394e2ae7f 91 for (int loop = 0; loop < 512; loop++) {
AjK 12:8c7394e2ae7f 92 uart.printf("%c", c);
AjK 12:8c7394e2ae7f 93 c++;
AjK 12:8c7394e2ae7f 94 if (c > 'Z') c = 'A';
AjK 12:8c7394e2ae7f 95 }
AjK 12:8c7394e2ae7f 96
AjK 12:8c7394e2ae7f 97 led1 = 0; // Show the end of sending by switching off LED1.
AjK 12:8c7394e2ae7f 98
AjK 12:8c7394e2ae7f 99 // End program. Flash LED4. Notice how LED 2 and 3 continue
AjK 12:8c7394e2ae7f 100 // to flash for a short period while the interrupt system
AjK 12:8c7394e2ae7f 101 // continues to send the characters left in the TX buffer.
AjK 12:8c7394e2ae7f 102
AjK 12:8c7394e2ae7f 103 while(1) {
AjK 12:8c7394e2ae7f 104 led4 = !led4;
AjK 12:8c7394e2ae7f 105 wait(0.25);
AjK 12:8c7394e2ae7f 106 }
AjK 12:8c7394e2ae7f 107 }
AjK 12:8c7394e2ae7f 108
AjK 12:8c7394e2ae7f 109 /*
AjK 12:8c7394e2ae7f 110 * Notes. Here is the sort of output you can expect on your PC/Mac/Linux host
AjK 12:8c7394e2ae7f 111 * machine that is connected to the "pc" USB serial port.
AjK 12:8c7394e2ae7f 112 *
AjK 12:8c7394e2ae7f 113 * *DMA* *DMA* *DMA* *DMA* *DMA* *DMA* *DMA* ABCDEFGHIJKLMNOPQRSTUVWXYZABCDE
AjK 12:8c7394e2ae7f 114 * FGHIJKLMNOPQRSTUVWXYZABCDEFGHIJKLMNOPQRSTUVWXYZABCDEFGHIJKLMNOPQRSTUVWXYZA
AjK 12:8c7394e2ae7f 115 * BCDEFGHIJKLMNOPQRSTUVWXYZABCDEFGHIJKLMNOPQRSTUVWXYZABCDEFGHIJKLMNOPQRSTUVW
AjK 12:8c7394e2ae7f 116 * XYZABCDEFGHIJKLMNOPQRSTUVWXYZABCDEFGHIJKLMNOPQRSTUVWXYZABCDEFGHIJKLMNOPQRS
AjK 12:8c7394e2ae7f 117 * TUVWXYZABCDEFGHIJKLMNOPQRSTUVWXYZABCDEFGHIJKLMNOPQRSTUVWXYZABCDEFGHIJKLMNO
AjK 12:8c7394e2ae7f 118 * PQRSTUVWXYZABCDEFGHIJKLMNOPQRSTUVWXYZABCDEFGHIJKLMNOPQRSTUVWXYZABCDEFGHIJK
AjK 12:8c7394e2ae7f 119 * LMNOPQRSTUVWXYZABCDEFGHIJKLMNOPQRSTUVWXYZABCDEFGHIJKLMNOPQRSTUVWXYZABCDEFG
AjK 12:8c7394e2ae7f 120 * HIJKLMNOPQRSTUVWXYZABCDEFGHIJKLMNOPQ Done. R
AjK 12:8c7394e2ae7f 121 *
AjK 12:8c7394e2ae7f 122 * Note how the DMA blocks the TX buffer sending under standard interrupt control.
AjK 12:8c7394e2ae7f 123 * Not until the DMA transfer is complete will "normal" buffered TX sending resume.
AjK 12:8c7394e2ae7f 124 *
AjK 12:8c7394e2ae7f 125 * Of interest is that last "R" character after the system has said "Done."
AjK 12:8c7394e2ae7f 126 * This comes from the fact that the TxEmpty callback is made when the TX buffer
AjK 12:8c7394e2ae7f 127 * becomes empty. MODSERIAL makes use of the fact that the Uarts built into the
AjK 12:8c7394e2ae7f 128 * LPC17xx device use a 16 byte FIFO on both RX and TX channels. This means that
AjK 12:8c7394e2ae7f 129 * when the TxEmpty callback is made, the TX buffer is empty, but that just means
AjK 12:8c7394e2ae7f 130 * the "last few characters" were written to the TX FIFO. So although the TX
AjK 12:8c7394e2ae7f 131 * buffer has gone empty, the Uart's transmit system is still sending any remaining
AjK 12:8c7394e2ae7f 132 * characters from it's TX FIFO. If you want to be truely sure all the characters
AjK 12:8c7394e2ae7f 133 * you have sent have left the Mbed then call txIsBusy(); This function will
AjK 12:8c7394e2ae7f 134 * return true if characters are still being sent. If it returns false after
AjK 12:8c7394e2ae7f 135 * the Tx buffer is empty then all your characters have been sent.
AjK 12:8c7394e2ae7f 136 *
AjK 12:8c7394e2ae7f 137 * In a similar way, when characters are received into the RX FIFO, the entire
AjK 12:8c7394e2ae7f 138 * FIFO contents is moved to the RX buffer, assuming there is room left in the
AjK 12:8c7394e2ae7f 139 * RX buffer. If there is not, any remaining characters are left in the RX FIFO
AjK 12:8c7394e2ae7f 140 * and will be moved to the RX buffer on the next interrupt or when the running
AjK 12:8c7394e2ae7f 141 * program removes a character(s) from the RX buffer with the getc() method.
AjK 12:8c7394e2ae7f 142 */
AjK 12:8c7394e2ae7f 143
AjK 12:8c7394e2ae7f 144 #endif