summaryrefslogtreecommitdiffstats
path: root/tmk_core/common/uart.c
blob: b29d3bbb94139aa29b1af0fc0356d8af59c2d6cf (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
// TODO: Teensy support(ATMega32u4/AT90USB128)
// Fixed for Arduino Duemilanove ATmega168p by Jun Wako
/* UART Example for Teensy USB Development Board
 * http://www.pjrc.com/teensy/
 * Copyright (c) 2009 PJRC.COM, LLC
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */

// Version 1.0: Initial Release
// Version 1.1: Add support for Teensy 2.0, minor optimizations

#include <avr/io.h>
#include <avr/interrupt.h>

#include "uart.h"

#if defined(__AVR_ATmega168__) || defined(__AVR_ATmega168P__) || defined(__AVR_ATmega328P__)
#    define UDRn UDR0
#    define UBRRnL UBRR0L
#    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 USARTn_UDRE_vect USART_UDRE_vect
#    define USARTn_RX_vect USART_RX_vect
#elif defined(__AVR_ATmega32U4__) || defined(__AVR_ATmega32U2__) || defined(__AVR_AT90USB646__) || defined(__AVR_AT90USB647__) || defined(__AVR_AT90USB1286__) || defined(__AVR_AT90USB1287__)
#    define UDRn UDR1
#    define UBRRnL UBRR1L
#    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 USARTn_UDRE_vect USART1_UDRE_vect
#    define USARTn_RX_vect USART1_RX_vect
#elif defined(__AVR_ATmega32A__)
#    define UDRn UDR
#    define UBRRnL UBRRL
#    define UCSRnA UCSRA
#    define UCSRnB UCSRB
#    define UCSRnC UCSRC
#    define U2Xn U2X
#    define RXENn RXEN
#    define TXENn TXEN
#    define RXCIEn RXCIE
#    define UCSZn1 UCSZ1
#    define UCSZn0 UCSZ0
#    define UDRIEn UDRIE
#    define USARTn_UDRE_vect USART_UDRE_vect
#    define USARTn_RX_vect USART_RX_vect
#endif

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

static volatile uint8_t tx_buffer[TX_BUFFER_SIZE];
static volatile uint8_t tx_buffer_head;
static volatile uint8_t tx_buffer_tail;
static volatile uint8_t rx_buffer[RX_BUFFER_SIZE];
static volatile uint8_t rx_buffer_head;
static volatile uint8_t rx_buffer_tail;

// Initialize the UART
void uart_init(uint32_t baud) {
    cli();
    UBRRnL         = (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();
}

// Transmit a byte
void uart_putchar(uint8_t c) {
    uint8_t i;

    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;
    UCSRnB         = (1 << RXENn) | (1 << TXENn) | (1 << RXCIEn) | (1 << UDRIEn);
    // sei();
}

// Receive a byte
uint8_t uart_getchar(void) {
    uint8_t c, i;

    while (rx_buffer_head == rx_buffer_tail)
        ;  // wait for character
    i = rx_buffer_tail + 1;
    if (i >= RX_BUFFER_SIZE) i = 0;
    c              = rx_buffer[i];
    rx_buffer_tail = i;
    return c;
}

// Return the number of bytes waiting in the receive buffer.
// Call this before uart_getchar() to check if it will need
// to wait for a byte to arrive.
uint8_t uart_available(void) {
    uint8_t head, tail;

    head = rx_buffer_head;
    tail = rx_buffer_tail;
    if (head >= tail) return head - tail;
    return RX_BUFFER_SIZE + head - tail;
}

// Transmit Interrupt
ISR(USARTn_UDRE_vect) {
    uint8_t i;

    if (tx_buffer_head == tx_buffer_tail) {
        // buffer is empty, disable transmit interrupt
        UCSRnB = (1 << RXENn) | (1 << TXENn) | (1 << RXCIEn);
    } else {
        i = tx_buffer_tail + 1;
        if (i >= TX_BUFFER_SIZE) i = 0;
        UDRn           = tx_buffer[i];
        tx_buffer_tail = i;
    }
}

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

    c = UDRn;
    i = rx_buffer_head + 1;
    if (i >= RX_BUFFER_SIZE) i = 0;
    if (i != rx_buffer_tail) {
        rx_buffer[i]   = c;
        rx_buffer_head = i;
    }
}