sergiotarxz/nuttx
1
0
Fork 0
Code Issues Pull Requests Releases Wiki Activity

Fix PIC32 timer source frequency

Browse Source 
git-svn-id: svn://svn.code.sf.net/p/nuttx/code/trunk@4146 42af7a65-404d-4744-a932-0658087f49c3
This commit is contained in:
patacongo 2011-12-07 23:38:23 +00:00
parent f45477ac99
commit 5072f4a553
2 changed files with 43 additions and 8 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

44
arch/mips/src/pic32mx/pic32mx-timerisr.c
View File

@ -59,28 +59,53 @@
* Definitions
****************************************************************************/
/* Timer Setup **************************************************************/
/* Timer 1 is a type A timer. Setting the TCS bit in the timer control
* register will select the SOSC as the clock source. Otherwise, PBCLOCK
* is the clock source.
*/
#ifdef BOARD_TIMER1_SOSC
# define TIMER1_SRC_FREQ BOARD_SOSC_FREQ
# define TIMER1_CON_TCS TIMER_CON_TCS
#else
# define TIMER1_SRC_FREQ BOARD_PBCLOCK
# define TIMER1_CON_TCS (0)
#endif
/* Select a timer 1 prescale value. Our goal is to select the timer MATCH
* register value given the board's SOSC clock frequency and the desired
* register value given the timer 1 input clock frequency and the desired
* system timer frequency:
*
* TIMER1_MATCH = BOARD_SOSC_FREQ / TIMER1_PRESCALE / CLOCKS_PER_SEC
* TIMER1_MATCH = TIMER1_SRC_FREQ / TIMER1_PRESCALE / CLOCKS_PER_SEC
*
* We want the largest possible value for MATCH that is less than 65,535, the
* maximum value for the 16-bit timer register:
*
* TIMER1_PRESCALE >= BOARD_SOSC_FREQ / CLOCKS_PER_SEC / 65535
* TIMER1_PRESCALE >= TIMER1_SRC_FREQ / CLOCKS_PER_SEC / 65535
*
* Timer 1 does not have very many options for the perscaler value. So we
* can pick the best by brute force. Example:
*
* Example 1. Given:
* BOARD_TIMER1_SOSC = Defined
* BOARD_SOSC_FREQ = 32768
* CLOCKS_PER_SEC = 100
* Then:
* OPTIMAL_PRESCALE = 1
* TIMER1_PRESCALE = 1
* TIMER1_MATCH = 328 -> 99.90 ticks/sec
* TIMER1_MATCH = 327 -> 100.3 ticks/sec
*
* Example 2. Given:
* BOARD_TIMER1_SOSC = Not defined
* BOARD_PBCLOCK = 60000000
* CLOCKS_PER_SEC = 100
* Then:
* OPTIMAL_PRESCALE = 9.2
* TIMER1_PRESCALE = 64
* TIMER1_MATCH = 9375 -> 100.0 ticks/sec
*/
#define OPTIMAL_PRESCALE (BOARD_SOSC_FREQ / CLOCKS_PER_SEC / 65535)
#define OPTIMAL_PRESCALE (TIMER1_SRC_FREQ / CLOCKS_PER_SEC / 65535)
#if OPTIMAL_PRESCALE <= 1
# define TIMER1_CON_TCKPS TIMER1_CON_TCKPS_1
# define TIMER1_PRESCALE 1
@ -97,7 +122,7 @@
# error "This timer frequency cannot be represented"
#endif
#define TIMER1_MATCH (BOARD_SOSC_FREQ / TIMER1_PRESCALE / CLOCKS_PER_SEC)
#define TIMER1_MATCH (TIMER1_SRC_FREQ / TIMER1_PRESCALE / CLOCKS_PER_SEC)
/****************************************************************************
* Private Types
@ -143,9 +168,12 @@ int up_timerisr(int irq, uint32_t *regs)
void up_timerinit(void)
{
/* Configure and enable TIMER1 -- source internal SOSC (TCS=0) */
/* Configure and enable TIMER1. Used the computed TCKPS divider and timer
* match valude. The source will be either the internal PBCLOCK (TCS=0) or
* the external SOSC (TCS=1)
*/
putreg32(TIMER1_CON_TCKPS, PIC32MX_TIMER1_CON);
putreg32((TIMER1_CON_TCKPS|TIMER1_CON_TCS), PIC32MX_TIMER1_CON);
putreg32(0, PIC32MX_TIMER1_CNT);
putreg32(TIMER1_MATCH-1, PIC32MX_TIMER1_PR);
putreg32(TIMER_CON_ON, PIC32MX_TIMER1_CONSET);

7
configs/sure-pic32mx/include/board.h
View File

@ -83,6 +83,13 @@
#define BOARD_WD_ENABLE 0 /* Watchdog is disabled */
#define BOARD_WD_PRESCALER 8 /* Watchdog pre-scaler */
/* Timer 1 is a type A timer and is used as system clock. It can be clocked
* with either the SOSC or the PBCLOCK. We will use the PBCLOCK because it
* is much more accurate.
*/
#undef BOARD_TIMER1_SOSC
/* LED definitions **********************************************************/
/* The Sure PIC32MX board has five LEDs. One (D4, lablel "Power") is not
* controllable by software. Four are controllable by software: