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
|
/* *****************************************************************************
* 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/>.
*
* Created: 12/18/09 02:38:35
* Copyright (c) 2009 Perry L. Hung. All rights reserved.
*
* ****************************************************************************/
/**
* @file usart.h
*
* @brief USART Definitions
*/
#ifndef _USART_H_
#define _USART_H_
/* Transmit procedure:
* 1. Enable the USART by writing the UE bit in USART_CR1 register to 1.
*
* 2. Program the M bit in USART_CR1 to define the word length.
*
* 3. Program the number of stop bits in USART_CR2.
*
* 4. Select DMA enable (DMAT) in USART_CR3 if Multi buffer Communication is
* to take place. Configure the DMA register as explained in multibuffer
* communication.
*
* 5. Select the desired baud rate using the USART_BRR register.
*
* 6. Set the TE bit in USART_CR1 to send an idle frame as first transmission.
*
* 7. Write the data to send in the USART_DR register (this clears the TXE
* bit). Repeat this for each data to be transmitted in case of single buffer.
*
* 8. After writing the last data into the USART_DR register, wait until TC=1.
* This indicates that the transmission of the last frame is complete. This is
* required for instance when the USART is disabled or enters the Halt mode to
* avoid corrupting the last transmission.
*
* Single byte communication
* Clearing the TXE bit is always performed by a write to the data register.
*
* The TXE bit is set by hardware and it indicates:
* ? The data has been moved from TDR to the shift register and the data transmission has
* started.
* ? The TDR register is empty.
* ? The next data can be written in the USART_DR register without overwriting the
* previous data.
* This flag generates an interrupt if the TXEIE bit is set.
*
* When a transmission is taking place, a write instruction to the USART_DR
* register stores the data in the TDR register and which is copied in the
* shift register at the end of the current transmission.
*
* When no transmission is taking place, a write instruction to the USART_DR
* register places the data directly in the shift register, the data
* transmission starts, and the TXE bit is immediately set.
*
* If a frame is transmitted (after the stop bit) and the TXE bit is set, the
* TC bit goes high. An interrupt is generated if the TCIE bit is set in the
* USART_CR1 register. After writing the last data into the USART_DR register,
* it is mandatory to wait for TC=1 before disabling the USART or causing the
* microcontroller to enter the low power mode (see Figure 241: TC/TXE behavior
* when transmitting).
*
* Clearing the TC bit is performed by the following software sequence:
* 1. A read from the USART_SR register
* 2. A write to the USART_DR register
*
*
* For now, use 8N1
*
* Baud rate is generated by programming the mantissa and fraction values of
* USARTDIV
*
* baud = fck / 16*USARTDIV
* Fck = PLK1 for USART2 and USART3 = 36MHz
* Fck = PCLK2 for USART1 = 72MHz
*
* Baud Actual USARTDIV_36MHZ Error USARTDIV_72MHZ Error
* 2400 2.400 937.5 0% 1875 0%
* 9600 9.600 234.375 0% 468.75 0%
* 19200 19.2 117.1875 0% 234.375 0%
* 57600 57.6 39.0625 0% 78.125 0.%
* 115200 115.384 19.5 0.15% 39.0625 0%
* 230400 230.769 9.75 0.16% 19.5 0.16%
* 460800 461.538 4.875 0.16% 9.75 0.16%
* 921600 923.076 2.4375 0.16% 4.875 0.16%
* 225000 2250 1 0% 2 0%
*
* */
#define NR_USARTS 0x3
#ifdef __cplusplus
extern "C"{
#endif
#define USART_MAX_BAUD 225000
void usart_init(uint8 usart_num, uint32 baud);
void usart_disable(uint8 usart_num);
void usart_putstr(uint8 usart_num, const char*);
void usart_putudec(uint8 usart_num, uint32 val);
void usart_putc(uint8 usart_num, uint8 ch);
uint32 usart_data_available(uint8 usart_num);
uint8 usart_getc(uint8 usart_num);
#ifdef __cplusplus
} // extern "C"
#endif
#endif
|
