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Refine timing calculations; use for serial baudrate calculation

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This commit is contained in:
Allen Hill 2023-09-10 16:48:48 -04:00
parent 4c19f27992
commit bcd07d0ffb
3 changed files with 35 additions and 13 deletions
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7
CMakeLists.txt
View File

@ -15,10 +15,10 @@ set(FREQSEL 16MHz CACHE STRING "Select the operating frequency")
set_property(CACHE FREQSEL PROPERTY STRINGS "20MHz" "16MHz")
if(FREQSEL MATCHES "20MHz")
set(F_CPU 20000000L)
set(FREQSEL 20000000L)
set(AVR_UPLOADTOOL_BASE_OPTIONS ${AVR_UPLOADTOOL_BASE_OPTIONS} -U osccfg:w:0x2:m)
else()
set(F_CPU 16000000L)
set(FREQSEL 16000000L)
set(AVR_UPLOADTOOL_BASE_OPTIONS ${AVR_UPLOADTOOL_BASE_OPTIONS} -U osccfg:w:0x1:m)
endif()
@ -115,9 +115,10 @@ target_link_options(mockingboard PUBLIC
-B "${attiny_atpack_SOURCE_DIR}/gcc/dev/${AVR_MCU}"
)
target_compile_definitions(mockingboard PRIVATE
F_CPU=${F_CPU}
FREQSEL=${FREQSEL}
CLK_PRESCALE=$<IF:$<BOOL:${CLK_PRESCALE}>,0x01,0x00>
CLK_PRESCALE_DIV=${CLK_PRESCALE_DIV}
__CLK_PRESCALE_DIV=__${CLK_PRESCALE_DIV}
TCB_CLKSEL=${TCB_CLKSEL}
)
target_compile_options(mockingboard PRIVATE

9
src/com232.c
View File

@ -20,12 +20,16 @@
along with this program. If not, see <https://www.gnu.org/licenses/>.
*/
#define USART_BAUD_RATE(BAUD_RATE) \
(uint16_t)((float)(F_CPU * 64 / (16 * (float)BAUD_RATE)) + 0.5)
#include <avr/interrupt.h>
#include <avr/io.h>
#include <avr/sfr_defs.h>
#include <stdint.h>
#include "com232.h"
#include "timing.h"
uint8_t RS232_RxCharBuffer[25], RS232_RxCharBegin, RS232_RxCharEnd;
uint8_t readkey;
@ -35,13 +39,16 @@ void RS232_Init(void) {
PORTMUX.CTRLB = PORTMUX_USART0_ALTERNATE_gc; // Use PA1/PA2 for TxD/RxD
PORTA.DIRSET = PIN1_bm;
PORTA.DIRCLR = PIN2_bm;
USART0.CTRLA = USART_RXCIE_bm; // Enable receive interrupts
USART0.CTRLB = USART_RXEN_bm | USART_TXEN_bm | // Enable Rx/Tx and set receive
USART_RXMODE_NORMAL_gc; // mode normal
USART0.CTRLC = USART_CMODE_ASYNCHRONOUS_gc | USART_PMODE_DISABLED_gc |
USART_CHSIZE_8BIT_gc |
USART_SBMODE_1BIT_gc; // Async UART with 8N1 config
USART0.BAUD = 256; // 250k baud rate (64*F_CPU/(16*250k)) for F_CPU = 16MHz
USART0.BAUD = USART_BAUD_RATE(250000);
}
ISR(USART0_RXC_vect) {

32
src/timing.h
View File

@ -1,14 +1,30 @@
#ifndef _TIMING_HPP_
#define _TIMING_HPP_
#if CLK_PRESCALE == 0x01
#error "Not implemented"
#else
#define __CLKCTRL_PDIV_2X_gc 2
#define __CLKCTRL_PDIV_4X_gc 4
#define __CLKCTRL_PDIV_8X_gc 8
#define __CLKCTRL_PDIV_16X_gc 16
#define __CLKCTRL_PDIV_32X_gc 32
#define __CLKCTRL_PDIV_64X_gc 64
#define __CLKCTRL_PDIV_6X_gc 6
#define __CLKCTRL_PDIV_10X_gc 10
#define __CLKCTRL_PDIV_12X_gc 12
#define __CLKCTRL_PDIV_24X_gc 24
#define __CLKCTRL_PDIV_48X_gc 48
#if F_CPU == 20000000L
#define CPU_CYCLE 50
#elif F_CPU == 16000000L
#define CPU_CYCLE 62.5
#if CLK_PRESCALE == 0x01
#define F_CPU (FREQSEL / __CLK_PRESCALE_DIV)
#define CYCLE_MUL __CLK_PRESCALE_DIV
#else
#define F_CPU (FREQSEL)
#define CYCLE_MUL 1
#endif
#if FREQSEL == 20000000L
#define CPU_CYCLE (50 * CYCLE_MUL)
#elif FREQSEL == 16000000L
#define CPU_CYCLE (62.5 * CYCLE_MUL)
#else
#error "Not implemented"
#endif
@ -47,5 +63,3 @@
#define AVCLAN_BIT_LENGTH (39.5e3 / TCB_TICK)
#endif
#endif