Lee Kai Xuan / mbed-os

mbed-os

Fork of mbed-os by erkin yucel

features/unsupported/tests/mbed/modserial/main.cpp@0:f269e3021894, 2016-10-23 (annotated)

Committer:
elessair
Date:
Sun Oct 23 15:10:02 2016 +0000
Revision:
0:f269e3021894
Initial commit

Who changed what in which revision?

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elessair 0:f269e3021894 1 /*
elessair 0:f269e3021894 2 * To run this test program, link p9 to p10 so the Serial loops
elessair 0:f269e3021894 3 * back and receives characters it sends.
elessair 0:f269e3021894 4 */
elessair 0:f269e3021894 5 #include "mbed.h"
elessair 0:f269e3021894 6 #include "MODSERIAL.h"
elessair 0:f269e3021894 7
elessair 0:f269e3021894 8 DigitalOut led1(LED1);
elessair 0:f269e3021894 9 DigitalOut led2(LED2);
elessair 0:f269e3021894 10 DigitalOut led3(LED3);
elessair 0:f269e3021894 11 DigitalOut led4(LED4);
elessair 0:f269e3021894 12
elessair 0:f269e3021894 13 MODSERIAL pc(USBTX, USBRX);
elessair 0:f269e3021894 14
elessair 0:f269e3021894 15 /*
elessair 0:f269e3021894 16 * As experiement, you can define MODSERIAL as show here and see what
elessair 0:f269e3021894 17 * effects it has on the LEDs.
elessair 0:f269e3021894 18 *
elessair 0:f269e3021894 19 * MODSERIAL uart(TX_PIN, RX_PIN, 512);
elessair 0:f269e3021894 20 * With this, the 512 characters sent can straight into the buffer
elessair 0:f269e3021894 21 * vary quickly. This means LED1 is only on briefly as the TX buffer
elessair 0:f269e3021894 22 * fills.
elessair 0:f269e3021894 23 *
elessair 0:f269e3021894 24 * MODSERIAL uart(TX_PIN, RX_PIN, 32);
elessair 0:f269e3021894 25 * With this, the buffer is smaller than the default 256 bytes and
elessair 0:f269e3021894 26 * therefore LED1 stays on much longer while the system waits for
elessair 0:f269e3021894 27 * room in the TX buffer.
elessair 0:f269e3021894 28 */
elessair 0:f269e3021894 29 MODSERIAL uart(p9, p10);
elessair 0:f269e3021894 30
elessair 0:f269e3021894 31 // This function is called when a character goes from the TX buffer
elessair 0:f269e3021894 32 // to the Uart THR FIFO register.
elessair 0:f269e3021894 33 void txCallback(MODSERIAL_IRQ_INFO *q) {
elessair 0:f269e3021894 34 led2 = !led2;
elessair 0:f269e3021894 35 }
elessair 0:f269e3021894 36
elessair 0:f269e3021894 37 // This function is called when TX buffer goes empty
elessair 0:f269e3021894 38 void txEmpty(MODSERIAL_IRQ_INFO *q) {
elessair 0:f269e3021894 39 led2 = 0;
elessair 0:f269e3021894 40 pc.puts(" Done. ");
elessair 0:f269e3021894 41 }
elessair 0:f269e3021894 42
elessair 0:f269e3021894 43 // This function is called when a character goes into the RX buffer.
elessair 0:f269e3021894 44 void rxCallback(MODSERIAL_IRQ_INFO *q) {
elessair 0:f269e3021894 45 led3 = !led3;
elessair 0:f269e3021894 46 pc.putc(uart.getc());
elessair 0:f269e3021894 47 }
elessair 0:f269e3021894 48
elessair 0:f269e3021894 49 int main() {
elessair 0:f269e3021894 50 int c = 'A';
elessair 0:f269e3021894 51
elessair 0:f269e3021894 52 // Ensure the baud rate for the PC "USB" serial is much
elessair 0:f269e3021894 53 // higher than "uart" baud rate below. (default: 9600)
elessair 0:f269e3021894 54 // pc.baud(9600);
elessair 0:f269e3021894 55
elessair 0:f269e3021894 56 // Use a deliberatly slow baud to fill up the TX buffer
elessair 0:f269e3021894 57 uart.baud(1200);
elessair 0:f269e3021894 58
elessair 0:f269e3021894 59 uart.attach(&txCallback, MODSERIAL::ModTxIrq);
elessair 0:f269e3021894 60 uart.attach(&rxCallback, MODSERIAL::ModRxIrq);
elessair 0:f269e3021894 61 uart.attach(&txEmpty, MODSERIAL::ModTxEmpty);
elessair 0:f269e3021894 62
elessair 0:f269e3021894 63 // Loop sending characters. We send 512
elessair 0:f269e3021894 64 // which is twice the default TX/RX buffer size.
elessair 0:f269e3021894 65
elessair 0:f269e3021894 66 led1 = 1; // Show start of sending with LED1.
elessair 0:f269e3021894 67
elessair 0:f269e3021894 68 for (int loop = 0; loop < 512; loop++) {
elessair 0:f269e3021894 69 uart.printf("%c", c);
elessair 0:f269e3021894 70 c++;
elessair 0:f269e3021894 71 if (c > 'Z') c = 'A';
elessair 0:f269e3021894 72 }
elessair 0:f269e3021894 73
elessair 0:f269e3021894 74 led1 = 0; // Show the end of sending by switching off LED1.
elessair 0:f269e3021894 75
elessair 0:f269e3021894 76 // End program. Flash LED4. Notice how LED 2 and 3 continue
elessair 0:f269e3021894 77 // to flash for a short period while the interrupt system
elessair 0:f269e3021894 78 // continues to send the characters left in the TX buffer.
elessair 0:f269e3021894 79
elessair 0:f269e3021894 80 while(1) {
elessair 0:f269e3021894 81 led4 = !led4;
elessair 0:f269e3021894 82 wait(0.25);
elessair 0:f269e3021894 83 }
elessair 0:f269e3021894 84 }
elessair 0:f269e3021894 85
elessair 0:f269e3021894 86 /*
elessair 0:f269e3021894 87 * Notes. Here is the sort of output you can expect on your PC/Mac/Linux host
elessair 0:f269e3021894 88 * machine that is connected to the "pc" USB serial port.
elessair 0:f269e3021894 89 *
elessair 0:f269e3021894 90 * ABCDEFGHIJKLMNOPQRSTUVWXYZABCDEFGHIJKLMNOPQRSTUVWXYZABCDEFGHIJKLMNOPQRSTUV
elessair 0:f269e3021894 91 * WXYZABCDEFGHIJKLMNOPQRSTUVWXYZABCDEFGHIJKLMNOPQRSTUVWXYZABCDEFGHIJKLMNOPQR
elessair 0:f269e3021894 92 * STUVWXYZABCDEFGHIJKLMNOPQRSTUVWXYZABCDEFGHIJKLMNOPQRSTUVWXYZABCDEFGHIJKLMN
elessair 0:f269e3021894 93 * OPQRSTUVWXYZABCDEFGHIJKLMNOPQRSTUVWXYZABCDEFGHIJKLMNOPQRSTUVWXYZABCDEFGHIJ
elessair 0:f269e3021894 94 * KLMNOPQRSTUVWXYZABCDEFGHIJKLMNOPQRSTUVWXYZABCDEFGHIJKLMNOPQRSTUVWXYZABCDEF
elessair 0:f269e3021894 95 * GHIJKLMNOPQRSTUVWXYZABCDEFGHIJKLMNOPQRSTUVWXYZABCDEFGHIJKLMNOPQRSTUVWXYZAB
elessair 0:f269e3021894 96 * CDEFGHIJKLMNOPQRSTUVWXYZABCDEFGHIJKLMNOPQRSTUVWXYZABCDEFGHIJKLMNOPQ Done. R
elessair 0:f269e3021894 97 *
elessair 0:f269e3021894 98 * Of interest is that last "R" character after the system has said "Done."
elessair 0:f269e3021894 99 * This comes from the fact that the TxEmpty callback is made when the TX buffer
elessair 0:f269e3021894 100 * becomes empty. MODSERIAL makes use of the fact that the Uarts built into the
elessair 0:f269e3021894 101 * LPC17xx device use a 16 byte FIFO on both RX and TX channels. This means that
elessair 0:f269e3021894 102 * when the TxEmpty callback is made, the TX buffer is empty, but that just means
elessair 0:f269e3021894 103 * the "last few characters" were written to the TX FIFO. So although the TX
elessair 0:f269e3021894 104 * buffer has gone empty, the Uart's transmit system is still sending any remaining
elessair 0:f269e3021894 105 * characters from it's TX FIFO. If you want to be truely sure all the characters
elessair 0:f269e3021894 106 * you have sent have left the Mbed then call txIsBusy(); This function will
elessair 0:f269e3021894 107 * return true if characters are still being sent. If it returns false after
elessair 0:f269e3021894 108 * the Tx buffer is empty then all your characters have been sent.
elessair 0:f269e3021894 109 *
elessair 0:f269e3021894 110 * In a similar way, when characters are received into the RX FIFO, the entire
elessair 0:f269e3021894 111 * FIFO contents is moved to the RX buffer, assuming there is room left in the
elessair 0:f269e3021894 112 * RX buffer. If there is not, any remaining characters are left in the RX FIFO
elessair 0:f269e3021894 113 * and will be moved to the RX buffer on the next interrupt or when the running
elessair 0:f269e3021894 114 * program removes a character(s) from the RX buffer with the getc() method.
elessair 0:f269e3021894 115 */