Derek Fukumori / MODSERIAL

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Fork of MODSERIAL by Andy K

example_dma.cpp@23:1236d0b64e71, 2012-07-13 (annotated)

Committer:
dfukumori
Date:
Fri Jul 13 01:09:23 2012 +0000
Revision:
23:1236d0b64e71
Parent:
12:8c7394e2ae7f 
Required commit -- no changes

Who changed what in which revision?

UserRevisionLine numberNew contents of line
dfukumori 23:1236d0b64e71 1 #ifdef COMPILE_EXAMPLE_CODE_MODSERIAL_MODDMA
dfukumori 23:1236d0b64e71 2
dfukumori 23:1236d0b64e71 3 /*
dfukumori 23:1236d0b64e71 4 * To run this test program, link p9 to p10 so the Serial loops
dfukumori 23:1236d0b64e71 5 * back and receives characters it sends.
dfukumori 23:1236d0b64e71 6 */
dfukumori 23:1236d0b64e71 7
dfukumori 23:1236d0b64e71 8 #include "mbed.h"
dfukumori 23:1236d0b64e71 9
dfukumori 23:1236d0b64e71 10 /* Note, this example requires that you also import into the Mbed
dfukumori 23:1236d0b64e71 11 compiler the MODDMA project as well as MODSERIAL
dfukumori 23:1236d0b64e71 12 http://mbed.org/users/AjK/libraries/MODDMA/latest
dfukumori 23:1236d0b64e71 13 MODDMA.h MUST come before MODSERIAL.h */
dfukumori 23:1236d0b64e71 14 #include "MODDMA.h" // <--- Declare first
dfukumori 23:1236d0b64e71 15 #include "MODSERIAL.h" // Flollowed by MODSERIAL
dfukumori 23:1236d0b64e71 16
dfukumori 23:1236d0b64e71 17 DigitalOut led1(LED1);
dfukumori 23:1236d0b64e71 18 DigitalOut led2(LED2);
dfukumori 23:1236d0b64e71 19 DigitalOut led3(LED3);
dfukumori 23:1236d0b64e71 20 DigitalOut led4(LED4);
dfukumori 23:1236d0b64e71 21
dfukumori 23:1236d0b64e71 22 MODSERIAL pc(USBTX, USBRX);
dfukumori 23:1236d0b64e71 23
dfukumori 23:1236d0b64e71 24 /*
dfukumori 23:1236d0b64e71 25 * As experiement, you can define MODSERIAL as show here and see what
dfukumori 23:1236d0b64e71 26 * effects it has on the LEDs.
dfukumori 23:1236d0b64e71 27 *
dfukumori 23:1236d0b64e71 28 * MODSERIAL uart(TX_PIN, RX_PIN, 512);
dfukumori 23:1236d0b64e71 29 * With this, the 512 characters sent can straight into the buffer
dfukumori 23:1236d0b64e71 30 * vary quickly. This means LED1 is only on briefly as the TX buffer
dfukumori 23:1236d0b64e71 31 * fills.
dfukumori 23:1236d0b64e71 32 *
dfukumori 23:1236d0b64e71 33 * MODSERIAL uart(TX_PIN, RX_PIN, 32);
dfukumori 23:1236d0b64e71 34 * With this, the buffer is smaller than the default 256 bytes and
dfukumori 23:1236d0b64e71 35 * therefore LED1 stays on much longer while the system waits for
dfukumori 23:1236d0b64e71 36 * room in the TX buffer.
dfukumori 23:1236d0b64e71 37 */
dfukumori 23:1236d0b64e71 38 MODSERIAL uart(TX_PIN, RX_PIN);
dfukumori 23:1236d0b64e71 39
dfukumori 23:1236d0b64e71 40 MODDMA dma;
dfukumori 23:1236d0b64e71 41
dfukumori 23:1236d0b64e71 42 // This function is called when a character goes from the TX buffer
dfukumori 23:1236d0b64e71 43 // to the Uart THR FIFO register.
dfukumori 23:1236d0b64e71 44 void txCallback(void) {
dfukumori 23:1236d0b64e71 45 led2 = !led2;
dfukumori 23:1236d0b64e71 46 }
dfukumori 23:1236d0b64e71 47
dfukumori 23:1236d0b64e71 48 // This function is called when TX buffer goes empty
dfukumori 23:1236d0b64e71 49 void txEmpty(void) {
dfukumori 23:1236d0b64e71 50 led2 = 0;
dfukumori 23:1236d0b64e71 51 pc.puts(" Done. ");
dfukumori 23:1236d0b64e71 52 }
dfukumori 23:1236d0b64e71 53
dfukumori 23:1236d0b64e71 54 void dmaComplete(void) {
dfukumori 23:1236d0b64e71 55 led1 = 1;
dfukumori 23:1236d0b64e71 56 }
dfukumori 23:1236d0b64e71 57
dfukumori 23:1236d0b64e71 58 // This function is called when a character goes into the RX buffer.
dfukumori 23:1236d0b64e71 59 void rxCallback(void) {
dfukumori 23:1236d0b64e71 60 led3 = !led3;
dfukumori 23:1236d0b64e71 61 pc.putc(uart.getc());
dfukumori 23:1236d0b64e71 62 }
dfukumori 23:1236d0b64e71 63
dfukumori 23:1236d0b64e71 64 int main() {
dfukumori 23:1236d0b64e71 65 char s1[] = " *DMA* *DMA* *DMA* *DMA* *DMA* *DMA* *DMA* ";
dfukumori 23:1236d0b64e71 66 int c = 'A';
dfukumori 23:1236d0b64e71 67
dfukumori 23:1236d0b64e71 68 // Tell MODSERIAL where the MODDMA controller is.
dfukumori 23:1236d0b64e71 69 pc.MODDMA( &dma );
dfukumori 23:1236d0b64e71 70
dfukumori 23:1236d0b64e71 71 // Ensure the baud rate for the PC "USB" serial is much
dfukumori 23:1236d0b64e71 72 // higher than "uart" baud rate below.
dfukumori 23:1236d0b64e71 73 pc.baud( PC_BAUD );
dfukumori 23:1236d0b64e71 74
dfukumori 23:1236d0b64e71 75 // Use a deliberatly slow baud to fill up the TX buffer
dfukumori 23:1236d0b64e71 76 uart.baud(1200);
dfukumori 23:1236d0b64e71 77
dfukumori 23:1236d0b64e71 78 uart.attach( &txCallback, MODSERIAL::TxIrq );
dfukumori 23:1236d0b64e71 79 uart.attach( &rxCallback, MODSERIAL::RxIrq );
dfukumori 23:1236d0b64e71 80 uart.attach( &txEmpty, MODSERIAL::TxEmpty );
dfukumori 23:1236d0b64e71 81
dfukumori 23:1236d0b64e71 82 // Loop sending characters. We send 512
dfukumori 23:1236d0b64e71 83 // which is twice the default TX/RX buffer size.
dfukumori 23:1236d0b64e71 84
dfukumori 23:1236d0b64e71 85 led1 = 0;
dfukumori 23:1236d0b64e71 86
dfukumori 23:1236d0b64e71 87 // Send the buffer s using DMA channel 7
dfukumori 23:1236d0b64e71 88 pc.attach_dmaSendComplete( &dmaComplete );
dfukumori 23:1236d0b64e71 89 pc.dmaSend( s1, sizeof(s1), MODDMA::Channel_7 );
dfukumori 23:1236d0b64e71 90
dfukumori 23:1236d0b64e71 91 for (int loop = 0; loop < 512; loop++) {
dfukumori 23:1236d0b64e71 92 uart.printf("%c", c);
dfukumori 23:1236d0b64e71 93 c++;
dfukumori 23:1236d0b64e71 94 if (c > 'Z') c = 'A';
dfukumori 23:1236d0b64e71 95 }
dfukumori 23:1236d0b64e71 96
dfukumori 23:1236d0b64e71 97 led1 = 0; // Show the end of sending by switching off LED1.
dfukumori 23:1236d0b64e71 98
dfukumori 23:1236d0b64e71 99 // End program. Flash LED4. Notice how LED 2 and 3 continue
dfukumori 23:1236d0b64e71 100 // to flash for a short period while the interrupt system
dfukumori 23:1236d0b64e71 101 // continues to send the characters left in the TX buffer.
dfukumori 23:1236d0b64e71 102
dfukumori 23:1236d0b64e71 103 while(1) {
dfukumori 23:1236d0b64e71 104 led4 = !led4;
dfukumori 23:1236d0b64e71 105 wait(0.25);
dfukumori 23:1236d0b64e71 106 }
dfukumori 23:1236d0b64e71 107 }
dfukumori 23:1236d0b64e71 108
dfukumori 23:1236d0b64e71 109 /*
dfukumori 23:1236d0b64e71 110 * Notes. Here is the sort of output you can expect on your PC/Mac/Linux host
dfukumori 23:1236d0b64e71 111 * machine that is connected to the "pc" USB serial port.
dfukumori 23:1236d0b64e71 112 *
dfukumori 23:1236d0b64e71 113 * *DMA* *DMA* *DMA* *DMA* *DMA* *DMA* *DMA* ABCDEFGHIJKLMNOPQRSTUVWXYZABCDE
dfukumori 23:1236d0b64e71 114 * FGHIJKLMNOPQRSTUVWXYZABCDEFGHIJKLMNOPQRSTUVWXYZABCDEFGHIJKLMNOPQRSTUVWXYZA
dfukumori 23:1236d0b64e71 115 * BCDEFGHIJKLMNOPQRSTUVWXYZABCDEFGHIJKLMNOPQRSTUVWXYZABCDEFGHIJKLMNOPQRSTUVW
dfukumori 23:1236d0b64e71 116 * XYZABCDEFGHIJKLMNOPQRSTUVWXYZABCDEFGHIJKLMNOPQRSTUVWXYZABCDEFGHIJKLMNOPQRS
dfukumori 23:1236d0b64e71 117 * TUVWXYZABCDEFGHIJKLMNOPQRSTUVWXYZABCDEFGHIJKLMNOPQRSTUVWXYZABCDEFGHIJKLMNO
dfukumori 23:1236d0b64e71 118 * PQRSTUVWXYZABCDEFGHIJKLMNOPQRSTUVWXYZABCDEFGHIJKLMNOPQRSTUVWXYZABCDEFGHIJK
dfukumori 23:1236d0b64e71 119 * LMNOPQRSTUVWXYZABCDEFGHIJKLMNOPQRSTUVWXYZABCDEFGHIJKLMNOPQRSTUVWXYZABCDEFG
dfukumori 23:1236d0b64e71 120 * HIJKLMNOPQRSTUVWXYZABCDEFGHIJKLMNOPQ Done. R
dfukumori 23:1236d0b64e71 121 *
dfukumori 23:1236d0b64e71 122 * Note how the DMA blocks the TX buffer sending under standard interrupt control.
dfukumori 23:1236d0b64e71 123 * Not until the DMA transfer is complete will "normal" buffered TX sending resume.
dfukumori 23:1236d0b64e71 124 *
dfukumori 23:1236d0b64e71 125 * Of interest is that last "R" character after the system has said "Done."
dfukumori 23:1236d0b64e71 126 * This comes from the fact that the TxEmpty callback is made when the TX buffer
dfukumori 23:1236d0b64e71 127 * becomes empty. MODSERIAL makes use of the fact that the Uarts built into the
dfukumori 23:1236d0b64e71 128 * LPC17xx device use a 16 byte FIFO on both RX and TX channels. This means that
dfukumori 23:1236d0b64e71 129 * when the TxEmpty callback is made, the TX buffer is empty, but that just means
dfukumori 23:1236d0b64e71 130 * the "last few characters" were written to the TX FIFO. So although the TX
dfukumori 23:1236d0b64e71 131 * buffer has gone empty, the Uart's transmit system is still sending any remaining
dfukumori 23:1236d0b64e71 132 * characters from it's TX FIFO. If you want to be truely sure all the characters
dfukumori 23:1236d0b64e71 133 * you have sent have left the Mbed then call txIsBusy(); This function will
dfukumori 23:1236d0b64e71 134 * return true if characters are still being sent. If it returns false after
dfukumori 23:1236d0b64e71 135 * the Tx buffer is empty then all your characters have been sent.
dfukumori 23:1236d0b64e71 136 *
dfukumori 23:1236d0b64e71 137 * In a similar way, when characters are received into the RX FIFO, the entire
dfukumori 23:1236d0b64e71 138 * FIFO contents is moved to the RX buffer, assuming there is room left in the
dfukumori 23:1236d0b64e71 139 * RX buffer. If there is not, any remaining characters are left in the RX FIFO
dfukumori 23:1236d0b64e71 140 * and will be moved to the RX buffer on the next interrupt or when the running
dfukumori 23:1236d0b64e71 141 * program removes a character(s) from the RX buffer with the getc() method.
dfukumori 23:1236d0b64e71 142 */
dfukumori 23:1236d0b64e71 143
dfukumori 23:1236d0b64e71 144 #endif