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uart.c fix from TMK #7628

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merged 2 commits into from
Feb 21, 2020
Merged

uart.c fix from TMK #7628

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e9df527
uart.c fix from TMK
drashna Dec 13, 2019
2d64a88
Avoid deadlock when uart.c is usind in ISR
drashna Dec 13, 2019
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54 changes: 44 additions & 10 deletions tmk_core/common/uart.c
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Original file line number Diff line number Diff line change
Expand Up @@ -31,9 +31,41 @@

#include "uart.h"

#if defined(__AVR_ATmega168__) || defined(__AVR_ATmega168P__) || defined(__AVR_ATmega328P__)
# define UDRn UDR0
# define UBRRn UBRR0
# define UCSRnA UCSR0A
# define UCSRnB UCSR0B
# define UCSRnC UCSR0C
# define U2Xn U2X0
# define RXENn RXEN0
# define TXENn TXEN0
# define RXCIEn RXCIE0
# define UCSZn1 UCSZ01
# define UCSZn0 UCSZ00
# define UDRIEn UDRIE0
# define UDRE_vect USART_UDRE_vect
# define RX_vect USART_RX_vect
#elif defined(__AVR_ATmega32U4__) || defined(__AVR_ATmega32U2__) || defined(__AVR_AT90USB1286__) || defined(__AVR_AT90USB1287__)
# define UDRn UDR1
# define UBRRn UBRR1
# define UCSRnA UCSR1A
# define UCSRnB UCSR1B
# define UCSRnC UCSR1C
# define U2Xn U2X1
# define RXENn RXEN1
# define TXENn TXEN1
# define RXCIEn RXCIE1
# define UCSZn1 UCSZ11
# define UCSZn0 UCSZ10
# define UDRIEn UDRIE1
# define UDRE_vect USART1_UDRE_vect
# define RX_vect USART1_RX_vect
#endif

// These buffers may be any size from 2 to 256 bytes.
#define RX_BUFFER_SIZE 64
#define TX_BUFFER_SIZE 40
#define TX_BUFFER_SIZE 256

static volatile uint8_t tx_buffer[TX_BUFFER_SIZE];
static volatile uint8_t tx_buffer_head;
Expand All @@ -45,10 +77,10 @@ static volatile uint8_t rx_buffer_tail;
// Initialize the UART
void uart_init(uint32_t baud) {
cli();
UBRR0 = (F_CPU / 4 / baud - 1) / 2;
UCSR0A = (1 << U2X0);
UCSR0B = (1 << RXEN0) | (1 << TXEN0) | (1 << RXCIE0);
UCSR0C = (1 << UCSZ01) | (1 << UCSZ00);
UBRRn = (F_CPU / 4 / baud - 1) / 2;
UCSRnA = (1 << U2Xn);
UCSRnB = (1 << RXENn) | (1 << TXENn) | (1 << RXCIEn);
UCSRnC = (1 << UCSZn1) | (1 << UCSZn0);
tx_buffer_head = tx_buffer_tail = 0;
rx_buffer_head = rx_buffer_tail = 0;
sei();
Expand All @@ -60,12 +92,14 @@ void uart_putchar(uint8_t c) {

i = tx_buffer_head + 1;
if (i >= TX_BUFFER_SIZE) i = 0;
// return immediately to avoid deadlock when interrupt is disabled(called from ISR)
if (tx_buffer_tail == i && (SREG & (1<<SREG_I)) == 0) return;
while (tx_buffer_tail == i)
; // wait until space in buffer
// cli();
tx_buffer[i] = c;
tx_buffer_head = i;
UCSR0B = (1 << RXEN0) | (1 << TXEN0) | (1 << RXCIE0) | (1 << UDRIE0);
UCSRB = (1 << RXENn) | (1 << TXENn) | (1 << RXCIEn) | (1 << UDRIEn);
// sei();
}

Expand Down Expand Up @@ -95,12 +129,12 @@ uint8_t uart_available(void) {
}

// Transmit Interrupt
ISR(USART_UDRE_vect) {
ISR(UDRE_vect) {
uint8_t i;

if (tx_buffer_head == tx_buffer_tail) {
// buffer is empty, disable transmit interrupt
UCSR0B = (1 << RXEN0) | (1 << TXEN0) | (1 << RXCIE0);
UCSRnB = (1 << RXENn) | (1 << TXENn) | (1 << RXCIEn);
} else {
i = tx_buffer_tail + 1;
if (i >= TX_BUFFER_SIZE) i = 0;
Expand All @@ -110,10 +144,10 @@ ISR(USART_UDRE_vect) {
}

// Receive Interrupt
ISR(USART_RX_vect) {
ISR(RX_vect) {
uint8_t c, i;

c = UDR0;
c = UDRn;
i = rx_buffer_head + 1;
if (i >= RX_BUFFER_SIZE) i = 0;
if (i != rx_buffer_tail) {
Expand Down