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Merged
xchrishawk merged 2 commits into from
Aug 29, 2025
Merged

Support additional USART baud rates. #21

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74fa557
Support additional USART baud rates.
xchrishawk Aug 29, 2025
e5ddd37
Remove BAUD macro that is no longer needed.
xchrishawk Aug 29, 2025
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4 changes: 2 additions & 2 deletions .vscode/c_cpp_properties.json
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Original file line number Diff line number Diff line change
Expand Up @@ -8,13 +8,13 @@
],
"defines": [
"MCU=\"atmega1284p\"",
"BAUD=19200",
"F_CPU=8000000",
"F_CPU=16000000",
"_DEBUG=1",
"_BUILD_TYPE=\"Debug\"",
"_FEATURE_ON=1",
"_FEATURE_OFF=0",
"_FEATURE_ENABLE_DEBUG_PORT=_FEATURE_ON",
"_FEATURE_OPT_DEBUG_PORT_BAUD=USART_BAUD_38400",
"_CONFIG_DFLT_WPM=200",
"_CONFIG_DFLT_WPM_ELEMENT_SCALE=1.0f",
"_CONFIG_DFLT_BUZZER_ENABLED=true",
Expand Down
3 changes: 0 additions & 3 deletions CMakeLists.txt
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Expand Up @@ -37,8 +37,6 @@ set(DEVICE_MCU atmega1284p
CACHE STRING "The MCU model to compile for.")
set(DEVICE_F_CPU 16000000
CACHE STRING "The device's CPU frequency, in Hz.")
set(DEVICE_BAUD 19200
CACHE STRING "The default USART baud rate, in bits per second.")

# -- Project Setup --

Expand Down Expand Up @@ -75,7 +73,6 @@ add_compile_definitions(
# Device information
MCU="${DEVICE_MCU}"
F_CPU=${DEVICE_F_CPU}
BAUD=${DEVICE_BAUD}
# Build type
_BUILD_TYPE="${CMAKE_BUILD_TYPE}"
$<$<CONFIG:Debug>:_DEBUG=1>
Expand Down
11 changes: 11 additions & 0 deletions configuration.cmake
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Expand Up @@ -18,6 +18,17 @@ add_compile_definitions(
_FEATURE_ENABLE_DEBUG_PORT=${FEATURE_ENABLE_DEBUG_PORT}
)

# -- Feature Options --

# Define values
set(FEATURE_OPT_DEBUG_PORT_BAUD USART_BAUD_38400
CACHE STRING "Baud rate for debug port. (usart_baud_t)")

# Set compile definitions
add_compile_definitions(
_FEATURE_OPT_DEBUG_PORT_BAUD=${FEATURE_OPT_DEBUG_PORT_BAUD}
)

# -- Configuration Defaults --

# Define values
Expand Down
1 change: 1 addition & 0 deletions src/main/application/debug_port.c
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Expand Up @@ -266,6 +266,7 @@ void debug_port_init( void )
usart_init( DEBUG_PORT_USART,
true,
true,
_FEATURE_OPT_DEBUG_PORT_BAUD,
USART_DATA_BITS_8,
USART_STOP_BITS_1,
USART_PARITY_DISABLED );
Expand Down
16 changes: 8 additions & 8 deletions src/main/drivers/gpio.c
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Expand Up @@ -24,19 +24,19 @@

// Helper macro for the register table below
#define gpio_reg( _port, _pin, _pcmsk_reg ) \
{ register_addr( DDR ## _port ), \
register_addr( PIN ## _port ), \
register_addr( PORT ## _port ), \
register_addr( PCMSK ## _pcmsk_reg ), \
{ register8_addr( DDR ## _port ), \
register8_addr( PIN ## _port ), \
register8_addr( PORT ## _port ), \
register8_addr( PCMSK ## _pcmsk_reg ), \
_pin }

// This array must be in the same order as the gpio_pin_t enumeration
static struct
{
register_t ddr_reg; /**< DDR register. */
register_t in_reg; /**< PIN register. */
register_t out_reg; /**< PORT register. */
register_t pcmsk_reg; /**< PCMSK register. */
register8_t ddr_reg; /**< DDR register. */
register8_t in_reg; /**< PIN register. */
register8_t out_reg; /**< PORT register. */
register8_t pcmsk_reg; /**< PCMSK register. */
uint8_t index; /**< Pin index in port. */
}
const s_reg_tbl[] =
Expand Down
141 changes: 93 additions & 48 deletions src/main/drivers/usart.c
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Expand Up @@ -18,7 +18,6 @@
#include <avr/interrupt.h>
#include <avr/io.h>
#include <util/delay.h>
#include <util/setbaud.h>

#include "core/sys.h"
#include "drivers/usart.h"
Expand All @@ -29,21 +28,23 @@
/* --------------------------------------------------- CONSTANTS ---------------------------------------------------- */

#define usart_reg( _idx ) \
{ register_addr( UDR ## _idx ), \
register_addr( UCSR ## _idx ## A ), \
register_addr( UCSR ## _idx ## B ), \
register_addr( UCSR ## _idx ## C ), \
register_addr( UBRR ## _idx ## H ), \
register_addr( UBRR ## _idx ## L ) }
{ register8_addr( UDR ## _idx ), \
register8_addr( UCSR ## _idx ## A ), \
register8_addr( UCSR ## _idx ## B ), \
register8_addr( UCSR ## _idx ## C ), \
register16_addr( UBRR ## _idx ), \
register8_addr( UBRR ## _idx ## H ), \
register8_addr( UBRR ## _idx ## L ) }

static struct
{
register_t udr; /**< The UDRn register for this USART. */
register_t ucsra; /**< The UCSRnA register for this USART. */
register_t ucsrb; /**< The UCSRnB register for this USART. */
register_t ucsrc; /**< The UCSRnC register for this USART. */
register_t ubrrh; /**< The UBRRnH register for this USART. */
register_t ubrrl; /**< The UBRRnL register for this USART. */
register8_t udr; /**< The UDRn register for this USART. */
register8_t ucsra; /**< The UCSRnA register for this USART. */
register8_t ucsrb; /**< The UCSRnB register for this USART. */
register8_t ucsrc; /**< The UCSRnC register for this USART. */
register16_t ubrr; /**< The UBRRn register for this USART. */
register8_t ubrrh; /**< The UBRRnH register for this USART. */
register8_t ubrrl; /**< The UBRRnL register for this USART. */
}
const s_reg_tbl[] =
{
Expand All @@ -69,14 +70,17 @@ _Static_assert( array_count( s_reg_tbl ) == USART_COUNT, "Invalid register table
/**
* @def TX_DELAY_US
* @brief The time to wait before trying again if the TX buffer is full, in microseconds.
* @note This macro uses `19200` as a conservative estimated baud rate.
*/
#define TX_DELAY_US ( ( ( USEC_PER_MSEC * MSEC_PER_SEC ) / ( unsigned int )BAUD ) * 2 )
#define TX_DELAY_US ( ( ( USEC_PER_MSEC * MSEC_PER_SEC ) / ( unsigned int )19200 ) * BITS_PER_BYTE )

/* ----------------------------------------------------- MACROS ----------------------------------------------------- */

// Validation macros
#define validate_usart( _usart ) \
assert_always( ( _usart ) < USART_COUNT )
#define validate_baud( _baud ) \
assert_always( ( _baud ) < USART_BAUD_COUNT )
#define validate_data_bits( _data_bits ) \
assert_always( ( _data_bits ) < USART_DATA_BITS_COUNT )
#define validate_parity( _parity ) \
Expand All @@ -95,6 +99,8 @@ _Static_assert( array_count( s_reg_tbl ) == USART_COUNT, "Invalid register table
( * ( s_reg_tbl[ ( _usart ) ].ucsrb ) )
#define UCSRC( _usart ) \
( * ( s_reg_tbl[ ( _usart ) ].ucsrc ) )
#define UBRR( _usart ) \
( * ( s_reg_tbl[ ( _usart ) ].ubrr ) )
#define UBRRH( _usart ) \
( * ( s_reg_tbl[ ( _usart ) ].ubrrh ) )
#define UBRRL( _usart ) \
Expand Down Expand Up @@ -149,12 +155,6 @@ static volatile size_t s_tx_tail[ USART_COUNT ];

/* ---------------------------------------------- PROCEDURE PROTOTYPES ---------------------------------------------- */

/**
* @fn autoconfigure_baud( usart_t )
* @brief Automatically configures the baud rate for the specified USART based on the `BAUD` macro.
*/
static void autoconfigure_baud( usart_t usart );

/**
* @fn isr_rx_complete( usart_t )
* @brief Runs the USART RX complete interrupt service routine for the specified USART.
Expand Down Expand Up @@ -185,6 +185,12 @@ static size_t rx_buf_avail( usart_t usart );
*/
static size_t rx_buf_count( usart_t usart );

/**
* @fn set_baud( usart_t, usart_baud_t )
* @brief Sets the baud rate for the specified USART.
*/
static void set_baud( usart_t usart, usart_baud_t baud );

/**
* @fn set_data_bits( usart_t, usart_data_bits_t )
* @brief Sets the data bits setting for the specified USART.
Expand Down Expand Up @@ -314,11 +320,13 @@ usart_error_t usart_get_errors( usart_t usart )
void usart_init( usart_t usart,
bool rx_enabled,
bool tx_enabled,
usart_baud_t baud,
usart_data_bits_t data_bits,
usart_stop_bits_t stop_bits,
usart_parity_t parity )
{
validate_usart( usart );
validate_baud( baud );
validate_data_bits( data_bits );
validate_stop_bits( stop_bits );
validate_parity( parity );
Expand All @@ -332,7 +340,7 @@ void usart_init( usart_t usart,
TX_TAIL( usart ) = 0;

// Configure USART
autoconfigure_baud( usart );
set_baud( usart, baud );
set_data_bits( usart, data_bits );
set_stop_bits( usart, stop_bits );
set_parity( usart, parity );
Expand All @@ -347,20 +355,6 @@ void usart_init( usart_t usart,
} /* usart_init() */


size_t usart_max_rx_size( void )
{
return( RX_BUF_SIZE );

} /* usart_max_rx_size() */


size_t usart_max_tx_size( void )
{
return( TX_BUF_SIZE );

} /* usart_max_tx_size() */


size_t usart_rx( usart_t usart, byte_t * data, size_t max_size )
{
validate_usart( usart );
Expand Down Expand Up @@ -449,19 +443,6 @@ size_t usart_tx_str( usart_t usart, char const * str, usart_wait_mode_t wait_mod
} /* usart_tx_str() */


static void autoconfigure_baud( usart_t usart )
{
UBRRH( usart ) = UBRRH_VALUE;
UBRRL( usart ) = UBRRL_VALUE;
#if( USE_2X )
set_bit( UCSRA( usart ), U2X0 );
#else
clear_bit( UCSRA( usart ), U2X0 );
#endif

} /* autoconfigure_baud() */


static void isr_rx_complete( usart_t usart, event_t event )
{
// If the buffer is full, drop the oldest received byte
Expand Down Expand Up @@ -523,6 +504,70 @@ static size_t rx_buf_count( usart_t usart )
} /* rx_buf_count() */


static void set_baud( usart_t usart, usart_baud_t baud )
{
_Static_assert( F_CPU == 16000000UL, "Baud settings depend on F_CPU of 16 MHz!" );

// Always enable 2X setting
set_bit( UCSRA( usart ), U2X0 );

// Set UBRR register based on selected baud rate
// These are taken from table 19-12 in the ATmega1283P data sheet:
// https://ww1.microchip.com/downloads/en/DeviceDoc/ATmega164A_PA-324A_PA-644A_PA-1284_P_Data-Sheet-40002070B.pdf
switch( baud )
{
case USART_BAUD_2400:
UBRR( usart ) = 832;
break;

case USART_BAUD_4800:
UBRR( usart ) = 416;
break;

case USART_BAUD_9600:
UBRR( usart ) = 207;
break;

case USART_BAUD_14400:
UBRR( usart ) = 138;
break;

case USART_BAUD_19200:
UBRR( usart ) = 103;
break;

case USART_BAUD_28800_NOT_RECOMMENDED:
UBRR( usart ) = 68;
break;

case USART_BAUD_38400:
UBRR( usart ) = 51;
break;

case USART_BAUD_57600_NOT_RECOMMENDED:
UBRR( usart ) = 34;
break;

case USART_BAUD_76800:
UBRR( usart ) = 25;
break;

case USART_BAUD_115200_NOT_RECOMMENDED:
UBRR( usart ) = 16;
break;

case USART_BAUD_230400_NOT_RECOMMENDED:
UBRR( usart ) = 8;
break;

case USART_BAUD_250000:
UBRR( usart ) = 7;
break;
}

} /* set_baud() */


static void set_data_bits( usart_t usart, usart_data_bits_t data_bits )
{
// Note that UCSZn2 is in UCSRnB, not UCSRnC
Expand Down
40 changes: 27 additions & 13 deletions src/main/drivers/usart.h
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Expand Up @@ -34,6 +34,31 @@ enum
USART_COUNT, /**< Number of valid USARTs. */
};

/**
* @typedef usart_baud_t
* @brief Enumeration of the supported USART baud settings.
* @note The approximate error percentage for each setting is indicated in the comment. Baud settings with an error
* of more than 0.5% are not recommended.
*/
typedef uint8_t usart_baud_t;
enum
{
USART_BAUD_2400, /**< 2400 baud (0.0% error). */
USART_BAUD_4800, /**< 4800 baud (-0.1% error). */
USART_BAUD_9600, /**< 9600 baud (0.2% error). */
USART_BAUD_14400, /**< 14400 baud (-0.1% error). */
USART_BAUD_19200, /**< 19200 baud (0.2% error). */
USART_BAUD_28800_NOT_RECOMMENDED, /**< 28800 baud (0.6% error - N/R). */
USART_BAUD_38400, /**< 38400 baud (0.2% error). */
USART_BAUD_57600_NOT_RECOMMENDED, /**< 57600 baud (-0.8% error - N/R). */
USART_BAUD_76800, /**< 76800 baud (0.2% error). */
USART_BAUD_115200_NOT_RECOMMENDED, /**< 115200 baud (2.1% error - N/R). */
USART_BAUD_230400_NOT_RECOMMENDED, /**< 230400 baud (-3.5% error - N/R). */
USART_BAUD_250000, /**< 250000 baud (0.0% error). */

USART_BAUD_COUNT, /**< Number of valid USART baud settings. */
};

/**
* @typedef usart_data_bits_t
* @brief Enumeration of the supported data bits settings for the USARTs.
Expand Down Expand Up @@ -126,29 +151,18 @@ void usart_deinit( usart_t usart );
usart_error_t usart_get_errors( usart_t usart );

/**
* @fn usart_init( usart_t, bool, bool, usart_data_bits_t, usart_stop_bits_t, usart_parity_t )
* @fn usart_init( usart_t, bool, bool, usart_baud_t, usart_data_bits_t, usart_stop_bits_t, usart_parity_t )
* @brief Initializes the specified USART with the specified configuration.
* @note Must be called prior to attempting any use of the USART.
*/
void usart_init( usart_t usart,
bool rx_enabled,
bool tx_enabled,
usart_baud_t baud,
usart_data_bits_t data_bits,
usart_stop_bits_t stop_bits,
usart_parity_t parity );

/**
* @fn usart_max_rx_size( void )
* @brief Returns the maximum supported RX buffer size for all USARTs.
*/
size_t usart_max_rx_size( void );

/**
* @fn usart_max_tx_size( void )
* @brief Returns the maximum supported TX buffer size for all USARTs.
*/
size_t usart_max_tx_size( void );

/**
* @fn usart_rx( usart_t, byte_t *, size_t )
* @brief Receives up to `max_size` bytes from the RX buffer for the specified USART.
Expand Down
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