FreeCalypso > hg > freecalypso-tools

annotate target-utils/buzplayer/timer.c @ 731:d89b72f2181b

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doc/TIFFS-IVA-usage: new decode facility documented
author Mychaela Falconia <falcon@freecalypso.org>
date Fri, 28 Aug 2020 05:56:13 +0000
parents e3d40f49d8c4
children
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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 }