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Change softserial timer calculation code to support baud rates in the

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range 600 to 19200 (tested)
This commit is contained in:
Dominic Clifton 2014-04-03 12:40:17 +01:00
parent 06554338d1
commit c36d884899
4 changed files with 32 additions and 11 deletions
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26
src/drv_softserial.c
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@ -1,8 +1,5 @@
#include "board.h"
// There needs to be a table of timerMhz per baud rate so the system can set the timer correctly.
// See http://www.wormfood.net/avrbaudcalc.php?postbitrate=19200&postclock=72
// Currently defaulting to 3Mhz to support 19200.
#define SOFT_SERIAL_TIMER_MHZ 3
#define SOFT_SERIAL_1_TIMER_RX_HARDWARE 4
#define SOFT_SERIAL_1_TIMER_TX_HARDWARE 5
@ -74,10 +71,29 @@ void serialInputPortConfig(const timerHardware_t *timerHardwarePtr)
#define TICKS_PER_BIT 3
bool isTimerPeriodTooLarge(uint32_t timerPeriod)
{
return timerPeriod > 0xFFFF;
}
void serialTimerConfig(const timerHardware_t *timerHardwarePtr, uint32_t baud, uint8_t reference, timerCCCallbackPtr callback)
{
uint16_t timerPeriod = (SOFT_SERIAL_TIMER_MHZ * 1000000) / (baud * TICKS_PER_BIT);
timerInConfig(timerHardwarePtr, timerPeriod, SOFT_SERIAL_TIMER_MHZ);
uint32_t clock = SystemCoreClock;
uint32_t timerPeriod;
do {
timerPeriod = clock / (baud * TICKS_PER_BIT);
if (isTimerPeriodTooLarge(timerPeriod)) {
if (clock > 1) {
clock = clock / 2;
} else {
// TODO unable to continue, unable to determine clock and timerPeriods for the given baud
}
}
} while (isTimerPeriodTooLarge(timerPeriod));
uint8_t mhz = SystemCoreClock / 1000000;
timerInConfig(timerHardwarePtr, timerPeriod, mhz);
configureTimerCaptureCompareInterrupt(timerHardwarePtr, reference, callback);
}