STM32F1xx micro-controller C firmware template
You can not select more than 25 topics Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
 
 
stm32f1/lib/usart_enhanced.c

185 lines
7.8 KiB

/* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*
*/
/** library for enhanced USART communication (code)
* @file usart_enhanced.c
* @author King Kévin <kingkevin@cuvoodoo.info>
* @date 2018
* @details the USART peripherals only support 8 or 9-bit word and even or odd parity (included in the data bits). The library adds support for 5 to 8-bit words, none/even/odd/mark/space parity (on top of the data bits)
* @note since parity is handled in software, the parity error (PE) flag is unused and should be replaced by the value return by usart_enhanced_parity_error
* @remark 9-bit raw communication is not supported since this is not common and can be done without this library
*/
/* standard libraries */
#include <stdint.h> // standard integer types
/* STM32 (including CM3) libraries */
#include <libopencm3/stm32/usart.h> // USART utilities
/* own libraries */
#include "usart_enhanced.h" // utilities for USART enhancements
/** number of available USART peripherals */
#define USART_PERIPHERALS_NB 3
/** configured enhanced USART word size */
static uint8_t usart_enhanced_databits[USART_PERIPHERALS_NB];
/** configured enhanced USART parity */
static enum usart_enhanced_parity_t usart_enhanced_parity[USART_PERIPHERALS_NB];
/** last enhanced USART parity error status */
static bool usart_enhanced_parity_errors[USART_PERIPHERALS_NB];
/** know if there is an even number of 1's in a integer
* @remark a look-up is a lot faster than making the calculation and doesn't does a lot of (flash) space
*/
static const bool even_parity_lut[256] = { true, false, false, true, false, true, true, false, false, true, true, false, true, false, false, true, false, true, true, false, true, false, false, true, true, false, false, true, false, true, true, false, false, true, true, false, true, false, false, true, true, false, false, true, false, true, true, false, true, false, false, true, false, true, true, false, false, true, true, false, true, false, false, true, false, true, true, false, true, false, false, true, true, false, false, true, false, true, true, false, true, false, false, true, false, true, true, false, false, true, true, false, true, false, false, true, true, false, false, true, false, true, true, false, false, true, true, false, true, false, false, true, false, true, true, false, true, false, false, true, true, false, false, true, false, true, true, false, false, true, true, false, true, false, false, true, true, false, false, true, false, true, true, false, true, false, false, true, false, true, true, false, false, true, true, false, true, false, false, true, true, false, false, true, false, true, true, false, false, true, true, false, true, false, false, true, false, true, true, false, true, false, false, true, true, false, false, true, false, true, true, false, true, false, false, true, false, true, true, false, false, true, true, false, true, false, false, true, false, true, true, false, true, false, false, true, true, false, false, true, false, true, true, false, false, true, true, false, true, false, false, true, true, false, false, true, false, true, true, false, true, false, false, true, false, true, true, false, false, true, true, false, true, false, false, true, };
/** get index of corresponding enhanced USART configurations
* @param[in] usart USART peripheral base address
* @return index used for the individual USART configurations
* @note the returned value is valid only is less than USART_PERIPHERALS_NB
*/
static uint8_t usart_enhanced_id(uint32_t usart)
{
uint8_t to_return = USART_PERIPHERALS_NB;
switch (usart) {
case USART1:
to_return = 0;
break;
case USART2:
to_return = 1;
break;
case USART3:
to_return = 2;
break;
default:
to_return = USART_PERIPHERALS_NB;
break;
}
return to_return;
}
bool usart_enhanced_config(uint32_t usart, uint8_t databits, enum usart_enhanced_parity_t parity)
{
/* sanity check */
uint8_t id = usart_enhanced_id(usart);
if (id>=USART_PERIPHERALS_NB) {
return false;
}
if (databits<5 || databits>8) {
return false;
}
if (parity>USART_ENHANCED_PARITY_SPACE) {
return false;
}
// save configuration for later use
usart_enhanced_databits[id] = databits;
usart_enhanced_parity[id] = parity;
// configure USART peripheral
if (8==databits && USART_ENHANCED_PARITY_NONE!=parity) { // the parity bit is additional to the data bits
usart_set_databits(usart, 9);
} else {
usart_set_databits(usart, 8);
}
usart_set_parity(usart, USART_PARITY_NONE); // set no parity since we will take care of it ourselves
// we could also lower the number of stop bits when less than 8 bits are used, for higher throughput, but this is not a good idea since most UART transceiver parse 8 bits even is less is used
return true;
}
void usart_enhanced_send(uint32_t usart, uint8_t data)
{
/* sanity check */
uint8_t id = usart_enhanced_id(usart);
if (id>=USART_PERIPHERALS_NB) {
return;
}
data &= ~(0xff<<usart_enhanced_databits[id]); // only keep the data bits
uint16_t output = data; // put value in output buffer
switch (usart_enhanced_parity[id]) {
case USART_ENHANCED_PARITY_NONE: // a mark is also decoded as idle/stop
case USART_ENHANCED_PARITY_MARK:
output |= (1<<usart_enhanced_databits[id]); // add idle state
break;
case USART_ENHANCED_PARITY_EVEN:
if (!even_parity_lut[data]) {
output |= (1<<usart_enhanced_databits[id]);
}
// no need to clear a bit if the parity is even
break;
case USART_ENHANCED_PARITY_ODD:
if (even_parity_lut[data]) {
output |= (1<<usart_enhanced_databits[id]);
}
// no need to clear a bit if the parity is odd
break;
case USART_ENHANCED_PARITY_SPACE:
// no need to clear the bit
break;
}
output |= (0xffff<<(usart_enhanced_databits[id]+1)); // set additional bits to idle (high)
usart_send(usart, output); // transmit character
}
uint8_t usart_enhanced_recv(uint32_t usart)
{
/* sanity check */
uint8_t id = usart_enhanced_id(usart);
if (id>=USART_PERIPHERALS_NB) {
return 0xff;
}
uint16_t input = usart_recv(usart); // read received character (also clears the error flags)
input &= ~(0xffff<<(usart_enhanced_databits[id]+1)); // only keep the data bits + parity bit
// check the parity
uint16_t parity = input&(1<<usart_enhanced_databits[id]); // only keep the parity bit
usart_enhanced_parity_errors[id] = false;
switch (usart_enhanced_parity[id]) {
case USART_ENHANCED_PARITY_NONE:
usart_enhanced_parity_errors[id] = false;
break;
case USART_ENHANCED_PARITY_EVEN:
if (parity) {
usart_enhanced_parity_errors[id] = !even_parity_lut[input&0xff];
} else {
usart_enhanced_parity_errors[id] = even_parity_lut[input&0xff];
}
break;
case USART_ENHANCED_PARITY_ODD:
if (parity) {
usart_enhanced_parity_errors[id] = even_parity_lut[input&0xff];
} else {
usart_enhanced_parity_errors[id] = !even_parity_lut[input&0xff];
}
break;
case USART_ENHANCED_PARITY_MARK:
usart_enhanced_parity_errors[id] = !parity;
break;
case USART_ENHANCED_PARITY_SPACE:
usart_enhanced_parity_errors[id] = parity;
break;
}
input &= ~(0xffff<<(usart_enhanced_databits[id])); // only keep the data bits
return input;
}
bool usart_enhanced_parity_error(uint32_t usart)
{
/* sanity check */
uint8_t id = usart_enhanced_id(usart);
if (id>=USART_PERIPHERALS_NB) {
return false;
}
return usart_enhanced_parity_errors[id];
}