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Merge pull request #5 from mrnuke/stellaris-lcd
examples/lm4f/stellaris: Add LCD printf example
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‎examples/tiva/lm4f/stellaris-ek-lm4f120xl/lcd-hd44780-printf/Makefile

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##
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## This file is part of the libopencm3 project.
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##
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## Copyright (C) 2016 Alexandru Gagniuc <[email protected]>
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##
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## This library is free software: you can redistribute it and/or modify
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## it under the terms of the GNU Lesser General Public License as published by
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## the Free Software Foundation, either version 3 of the License, or
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## (at your option) any later version.
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##
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## This library is distributed in the hope that it will be useful,
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## but WITHOUT ANY WARRANTY; without even the implied warranty of
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## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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## GNU Lesser General Public License for more details.
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##
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## You should have received a copy of the GNU Lesser General Public License
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## along with this library. If not, see <http://www.gnu.org/licenses/>.
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##
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BINARY = lcd-hd44780-printf
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LDSCRIPT = ../ek-lm4f120xl.ld
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OBJS += hd44780-gpio.o stellaris_vfd.o uart.o
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include ../../Makefile.include

‎examples/tiva/lm4f/stellaris-ek-lm4f120xl/lcd-hd44780-printf/README.md

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# README
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This example demonstrates interfacing the Stellaris board to any HD44780 style
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LCD display, using an 8-bit data bus. It demonstrates the use of LCDs or VFDs
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(Vacuum Fluorescent Displays) driven by a HD44780 controller. It also
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demonstrates the use of printf-like functionality to print data to the display.
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While this example has been split up in component parts, it is complex, and
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contains many parts. If you're only looking for an example on how to use the
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UART, see uart_echo_simple, and uart_echo_interrupt examples instead.
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## HD44780 diplay control
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The HD44780 interface is split into two parts:
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### hd44780-gpio.[ch]
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These files provide a generic, object-oriented interface to talk to HD44780
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display controllers. It abstracts the communication interface into several easy
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to use functions, ranging from low-level control of the communication lines, to
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high-level control of the data to be displayed. The driver is named
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hd44780-gpio because the communication is driven via GPIO (as opposed to using
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an external bus).
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Hardware-specific details, such as driving the GPIO lines are not implemented
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here, but are instead outsourced to hardware-specific drivers. A
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hardware-specific driver can be provided by filling up a hd44870_lcd structure.
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This structure is also the context for every function in the generic display
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code.
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The hd44780-gpio aims to be a minimalistic driver, and does not aim to impement
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all the bells and whistles of the HD44780 controller, nor is it guaranteed to
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work on all display geometries (but it's pretty easy to adapt).
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### stellaris_vfd.c
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This file implements the hardware-specific part of the display driver. It
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provides initialization of the GPIO lines, and controls the communication lines
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leading to the display. It also implements other hardware details, such as
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delays, and details about the geometry of the display.
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## UART control
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This example uses UART0 send and receive data. It also echoes back any data
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received. The echo happens within the UART interrupt routine. See
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uart_echo_interrupt for a simpler example on using UART interrupts.
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The uart.c file also keeps tracks of the numbers of received and sent bytes,
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and provides a way to report them to the application, as well as reset the
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counters.
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## Main application
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the application prints the "libopencm3" text on the first line of the display,
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followed by two special characters. The number of bytes sent and received over
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UART0 are displayed on the second line. The display is updated whenever one of
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the counters changes.
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The main application demonstrates how to use printf-like functionality to send
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data over the UART. It then demonstrates how to put simple strings on the
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display, and use the CGRAM (character generation RAM) of the HD44780 to create
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custom characters.
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The program's event loop demonstrates how to partition the display into
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subsections for displaying different information, using lcd_nprintf(), and
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lcd_printf(). With lcd_nprintf(), it is possible to print text to the LCD and
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confine it to a specified number of characters.
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## UART
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PA0 is the Rx pin, and PA1 is the Tx pin (from the LM4F perspective). These
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pins are connected to the CDCACM interface on the debug chip, so no hardware is
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necessary to test this example. Just connect the debug USB cable and use a
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terminal program to open the ACM port with 921600-8N1.
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For example:
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picocom /dev/ttyACM0 -b921600
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## Connections
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display data[0-7] <-> PB[0-7]
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display FNC -> PD4 (unused)
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display RS -> PD5
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display RW -> PD6
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display E -> PD7
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UART0 TX -> PA0
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UART0 RX <- PA1
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These connections were chosen such that writing to the data bus can be done
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with a single GPIO write. This is, however, not required, and GPIOs from
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different ports may be mixed to create the 8-bit data bus. Such changes should
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be reflected in the hardware-specific driver in stellaris_vfd.c .
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## Hardware
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This example was developed using a Noritake CU20025ECPB-U1J 2x20 vacuum
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fluorescent display.
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‎examples/tiva/lm4f/stellaris-ek-lm4f120xl/lcd-hd44780-printf/hd44780-gpio.c

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/*
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* This file is part of the libopencm3 project.
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*
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* Copyright (C) 2016 Alexandru Gagniuc <[email protected]>
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*
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* This library is free software: you can redistribute it and/or modify
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* it under the terms of the GNU Lesser General Public License as published by
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* the Free Software Foundation, either version 3 of the License, or
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* (at your option) any later version.
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*
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* This library is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public License
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* along with this library. If not, see <http://www.gnu.org/licenses/>.
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*/
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#include "hd44780-gpio.h"
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#include <stdarg.h>
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#include <stdio.h>
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#define MIN(x, y) ((x) < (y) ? (x) : (y))
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static void set_data_lines(struct hd44780_lcd *ctx, uint8_t data)
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{
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ctx->set_data_lines(ctx, data);
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}
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static void set_handshake_lines(struct hd44780_lcd *ctx,
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enum lcd_ctl_lines lines)
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{
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ctx->set_handshake_lines(ctx, lines);
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}
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static void ndelay(struct hd44780_lcd *ctx, unsigned int nano_sec)
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{
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ctx->ndelay(ctx, nano_sec);
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}
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void lcd_init(struct hd44780_lcd *ctx)
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{
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uint8_t function_bits;
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ctx->hardware_init(ctx);
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function_bits = HD44780_FUNCTION_8BIT;
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if (ctx->num_lines > 1)
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function_bits |= HD44780_FUNCTION_2LINES;
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lcd_send_command(ctx, HD44780_CMD_FUNCTION_SET | function_bits);
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/* VFD-specific: set brightness after sending FUNCTION_SET command */
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lcd_send_data(ctx, 0x02);
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/* Enable display. Disable cursor and blinker. */
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lcd_send_command(ctx, HD44780_CMD_DISPLAY_ON_OFF |
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HD44780_DISP_ONOFF_DISPLAY);
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lcd_send_command(ctx, HD44780_CMD_ENTRY_MODE_SET |
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HD44780_MODE_INCREMENT);
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}
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void lcd_clear_display(struct hd44780_lcd *ctx)
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{
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lcd_send_command(ctx, HD44780_CMD_CLEAR_DISPLAY);
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ndelay(ctx, 2300000);
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}
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void lcd_send_command(struct hd44780_lcd *ctx, uint8_t cmd)
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{
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set_handshake_lines(ctx, LINE_E);
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ndelay(ctx, 1000);
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set_data_lines(ctx, cmd);
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ndelay(ctx, 1000);
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set_handshake_lines(ctx, LINE_NONE);
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ndelay(ctx, 1000);
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}
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void lcd_send_data(struct hd44780_lcd *ctx, uint8_t data)
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{
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set_handshake_lines(ctx, LINE_E | LINE_RS);
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ndelay(ctx, 1000);
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set_data_lines(ctx, data);
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ndelay(ctx, 1000);
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set_handshake_lines(ctx, LINE_RS);
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ndelay(ctx, 1000);
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}
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void lcd_write_ddram(struct hd44780_lcd *ctx, uint8_t addr, uint8_t val)
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{
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lcd_send_command(ctx, HD44780_CMD_SET_DDRAM_ADDR | addr);
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lcd_send_data(ctx, val);
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}
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static void set_cgram_addr(struct hd44780_lcd *ctx, uint8_t addr)
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{
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addr &= HD44780_CMD_MASK(HD44780_CMD_SET_CGRAM_ADDR);
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lcd_send_command(ctx, HD44780_CMD_SET_CGRAM_ADDR | addr);
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}
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void lcd_write_cgram(struct hd44780_lcd *ctx, uint8_t addr, uint8_t val)
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{
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set_cgram_addr(ctx, addr);
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lcd_send_data(ctx, val);
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}
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void lcd_put_string(struct hd44780_lcd *ctx, uint8_t line, uint8_t start_char,
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const char *str)
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{
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unsigned int i;
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uint8_t addr;
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if (start_char >= ctx->line_len)
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return;
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addr = ctx->mem_line_stride * line + start_char;
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lcd_send_command(ctx, HD44780_CMD_SET_DDRAM_ADDR | addr);
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for (i = 0; i < (ctx->line_len - start_char); i++) {
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if (str[i] == '\0')
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break;
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lcd_send_data(ctx, str[i]);
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}
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}
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static void lcd_print_variadic(struct hd44780_lcd *ctx, uint8_t line,
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uint8_t start_char, uint8_t num_chars,
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const char *format, va_list args)
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{
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char buffer[64];
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int len;
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if (start_char >= ctx->line_len)
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return;
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len = MIN(ctx->line_len - start_char, num_chars);
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len = vsnprintf(buffer, len, format, args);
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lcd_put_string(ctx, line, start_char, buffer);
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}
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void lcd_printf(struct hd44780_lcd *ctx, uint8_t line, uint8_t start_char,
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const char *format, ...)
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{
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va_list args;
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va_start(args, format);
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lcd_print_variadic(ctx, line, start_char, ctx->line_len, format, args);
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va_end(args);
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}
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void lcd_nprintf(struct hd44780_lcd *ctx, uint8_t line, uint8_t start_char,
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uint8_t num_chars, const char *format, ...)
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{
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va_list args;
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va_start(args, format);
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lcd_print_variadic(ctx, line, start_char, num_chars, format, args);
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va_end(args);
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}
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void lcd_fill_cgram_character(struct hd44780_lcd *ctx, uint8_t char_idx,
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const uint8_t bitmap[8])
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{
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int i;
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if (char_idx > 7)
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return;
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set_cgram_addr(ctx, char_idx * 8);
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for (i = 0; i < 8; i++)
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lcd_send_data(ctx, bitmap[i]);
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}

‎examples/tiva/lm4f/stellaris-ek-lm4f120xl/lcd-hd44780-printf/hd44780-gpio.h

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/*
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* This file is part of the libopencm3 project.
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*
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* Copyright (C) 2016 Alexandru Gagniuc <[email protected]>
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*
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* This library is free software: you can redistribute it and/or modify
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* it under the terms of the GNU Lesser General Public License as published by
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* the Free Software Foundation, either version 3 of the License, or
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* (at your option) any later version.
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*
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* This library is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public License
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* along with this library. If not, see <http://www.gnu.org/licenses/>.
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*/
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#ifndef _HD44780_GPIO_H_
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#define _HD44780_GPIO_H_
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#include <stdint.h>
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#include <string.h>
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enum lcd_ctl_lines {
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LINE_NONE = 0,
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LINE_E = 1 << 0,
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LINE_RS = 1 << 1,
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LINE_WR = 1 << 2,
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};
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enum hd44780_commands {
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HD44780_CMD_CLEAR_DISPLAY = 1 << 0,
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HD44780_CMD_RETURN_HOME = 1 << 1,
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HD44780_CMD_ENTRY_MODE_SET = 1 << 2,
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HD44780_CMD_DISPLAY_ON_OFF = 1 << 3,
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HD44780_CMD_CURSOR_SHIFT = 1 << 4,
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HD44780_CMD_FUNCTION_SET = 1 << 5,
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HD44780_CMD_SET_CGRAM_ADDR = 1 << 6,
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HD44780_CMD_SET_DDRAM_ADDR = 1 << 7,
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};
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enum hd44780_function {
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HD44780_FUNCTION_8BIT = 1 << 4,
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HD44780_FUNCTION_2LINES = 1 << 3,
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HD44780_FUNCTION_FONT_5x8 = 1 << 2,
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};
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enum hd44780_disp_onoff {
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HD44780_DISP_ONOFF_DISPLAY = 1 << 2,
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HD44780_DISP_ONOFF_CURSOR = 1 << 1,
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HD44780_DISP_ONOFF_BLINKER = 1 << 0,
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};
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enum hd44780_entry_mode {
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HD44780_MODE_INCREMENT = 1 << 1,
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HD44780_MODE_SHIFT = 1 << 0,
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};
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#define HD44780_CMD_MASK(cmd) ((cmd) - 1)
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struct hd44780_lcd {
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void (*hardware_init)(struct hd44780_lcd *);
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void (*set_data_lines)(struct hd44780_lcd *, uint8_t data);
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void (*set_handshake_lines)(struct hd44780_lcd *, enum lcd_ctl_lines);
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void (*change_data_lines_mode_in)(struct hd44780_lcd *);
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void (*change_data_lines_mode_out)(struct hd44780_lcd *);
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void (*ndelay)(struct hd44780_lcd *, unsigned int nano_sec);
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void *priv;
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unsigned int num_lines;
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unsigned int line_len;
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unsigned int mem_line_stride;
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};
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void lcd_init(struct hd44780_lcd *ctx);
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void lcd_clear_display(struct hd44780_lcd *ctx);
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void lcd_write_ddram(struct hd44780_lcd *ctx, uint8_t addr, uint8_t val);
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void lcd_write_cgram(struct hd44780_lcd *ctx, uint8_t addr, uint8_t val);
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void lcd_send_command(struct hd44780_lcd *ctx, uint8_t cmd);
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void lcd_send_data(struct hd44780_lcd *ctx, uint8_t data);
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void lcd_put_string(struct hd44780_lcd *ctx, uint8_t line, uint8_t start_char,
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const char *str);
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void lcd_printf(struct hd44780_lcd *ctx, uint8_t line, uint8_t start_char,
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const char *format, ...);
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void lcd_nprintf(struct hd44780_lcd *ctx, uint8_t line, uint8_t start_char,
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uint8_t num_chars, const char *format, ...);
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void lcd_fill_cgram_character(struct hd44780_lcd *ctx, uint8_t char_idx,
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const uint8_t bitmap[8]);
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#endif /* _HD44780_GPIO_H_ */

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