FreeCalypso > hg > freecalypso-tools

annotate target-utils/buzplayer/timer.c @ 416:30f6d1c32c6f

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doc/Flash-boot-defect article removed (no longer relevant) This article is no longer relevant because the issue in question only affected one (1) defective FCDEV3B board which was not and never will be sold.
author Mychaela Falconia <falcon@freecalypso.org>
date Fri, 26 Oct 2018 07:11:08 +0000
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1 /*
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2 * FreeCalypso buzzer "melodies" have times measured in TDMA frames,
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3 * as that is the time unit in the main firmware which will ultimately
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4 * play them. In this standalone buzzer player we simulate TDMA frame
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5 * timing by programming Calypso TIMER1 with the period of 1875, and
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6 * we detect timer overflow (one virtual TDMA frame time having passed)
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7 * by polling the read register to avoid the need for interrupt handling
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8 * infrastructure.
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9 */
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10
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11 #include "types.h"
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12 #include "timer.h"
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13
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14 void
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15 timer_init()
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16 {
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17 TIMER1_REGS.cntl = CNTL_CLOCK_ENABLE;
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18 TIMER1_REGS.load = 1875;
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19 TIMER1_REGS.cntl = CNTL_CLOCK_ENABLE | CNTL_AUTO_RELOAD | CNTL_START;
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20 }
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22 void
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23 wait_for_tdma_frame()
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24 {
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25 u16 read1, read2;
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27 read1 = TIMER1_REGS.read;
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28 for (;;) {
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29 read2 = TIMER1_REGS.read;
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30 if (read2 > read1)
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31 return;
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32 read1 = read2;
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33 }
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34 }