1 /******************************************************************************
2 * Filename: uart.c
3 *
4 * Description: Driver for the UART peripheral.
5 *
6 * Copyright (c) 2022 Texas Instruments Incorporated
7 *
8 * Redistribution and use in source and binary forms, with or without
9 * modification, are permitted provided that the following conditions are met:
10 *
11 * 1) Redistributions of source code must retain the above copyright notice,
12 * this list of conditions and the following disclaimer.
13 *
14 * 2) Redistributions in binary form must reproduce the above copyright notice,
15 * this list of conditions and the following disclaimer in the documentation
16 * and/or other materials provided with the distribution.
17 *
18 * 3) Neither the name of the copyright holder nor the names of its
19 * contributors may be used to endorse or promote products derived from this
20 * software without specific prior written permission.
21 *
22 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
23 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
24 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
25 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
26 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
27 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
28 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
29 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
30 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
31 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
32 * POSSIBILITY OF SUCH DAMAGE.
33 *
34 ******************************************************************************/
35
36 #include "uart.h"
37
38 //*****************************************************************************
39 //
40 // Sets the configuration of a UART
41 //
42 //*****************************************************************************
UARTConfigSetExpClk(uint32_t base,uint32_t UARTClkFreq,uint32_t baudFreq,uint32_t config)43 void UARTConfigSetExpClk(uint32_t base, uint32_t UARTClkFreq, uint32_t baudFreq, uint32_t config)
44 {
45 uint32_t div;
46
47 // Check the arguments.
48 ASSERT(baudFreq != 0);
49
50 // Stop the UART.
51 UARTDisable(base);
52
53 // Compute the fractional baud rate divider.
54 div = (((UARTClkFreq * 8) / baudFreq) + 1) / 2;
55
56 // Set the baud rate.
57 HWREG(base + UART_O_IBRD) = div / 64;
58 HWREG(base + UART_O_FBRD) = div % 64;
59
60 // Set parity, data length, and number of stop bits.
61 HWREG(base + UART_O_LCRH) = config;
62 }
63
64 //*****************************************************************************
65 //
66 // Disables transmitting and receiving
67 //
68 //*****************************************************************************
UARTDisable(uint32_t base)69 void UARTDisable(uint32_t base)
70 {
71 // Wait for end of TX.
72 while (HWREG(base + UART_O_FR) & UART_FR_BUSY) {}
73
74 // Disable the FIFO.
75 HWREG(base + UART_O_LCRH) &= ~(UART_LCRH_FEN);
76
77 // Disable the UART.
78 HWREG(base + UART_O_CTL) &= ~(UART_CTL_UARTEN | UART_CTL_TXE | UART_CTL_RXE);
79 }
80
81 //*****************************************************************************
82 //
83 // Enable UART
84 //
85 //*****************************************************************************
UARTEnable(uint32_t base)86 void UARTEnable(uint32_t base)
87 {
88 // Enable the UART.
89 HWREG(base + UART_O_CTL) |= (UART_CTL_UARTEN | UART_CTL_TXE | UART_CTL_RXE);
90 }
91
92 //*****************************************************************************
93 //
94 // Blocks until a character is available, and returns it
95 //
96 //*****************************************************************************
UARTGetChar(uint32_t base)97 uint8_t UARTGetChar(uint32_t base)
98 {
99 // Wait until a char is available.
100 while (HWREG(base + UART_O_FR) & UART_FR_RXFE) {}
101
102 // Return the character.
103 return (HWREG(base + UART_O_DR));
104 }
105
106 //*****************************************************************************
107 //
108 // Blocks until there is space in the data register, and writes a byte to it
109 //
110 //*****************************************************************************
UARTPutChar(uint32_t base,uint8_t data)111 void UARTPutChar(uint32_t base, uint8_t data)
112 {
113 // Wait until space is available.
114 while (HWREG(base + UART_O_FR) & UART_FR_TXFF) {}
115
116 // Send the char.
117 HWREG(base + UART_O_DR) = data;
118 }
119
