133 lines
3.9 KiB
C
133 lines
3.9 KiB
C
// Commands for sending messages to a 4-bit hd44780 lcd driver
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//
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// Copyright (C) 2018 Kevin O'Connor <kevin@koconnor.net>
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//
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// This file may be distributed under the terms of the GNU GPLv3 license.
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#include "basecmd.h" // oid_alloc
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#include "board/gpio.h" // gpio_out_write
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#include "board/irq.h" // irq_disable
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#include "board/misc.h" // timer_from_us
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#include "command.h" // DECL_COMMAND
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#include "sched.h" // DECL_SHUTDOWN
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struct hd44780 {
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uint32_t last_cmd_time, cmd_wait_ticks;
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uint8_t last;
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struct gpio_out rs, e, d4, d5, d6, d7;
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};
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/****************************************************************
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* Transmit functions
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****************************************************************/
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// Write 4 bits to the hd44780 using the 4bit parallel interface
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static __always_inline void
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hd44780_xmit_bits(uint8_t toggle, struct gpio_out e, struct gpio_out d4
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, struct gpio_out d5, struct gpio_out d6, struct gpio_out d7)
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{
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gpio_out_toggle(e);
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if (toggle & 0x10)
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gpio_out_toggle(d4);
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if (toggle & 0x20)
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gpio_out_toggle(d5);
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if (toggle & 0x40)
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gpio_out_toggle(d6);
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if (toggle & 0x80)
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gpio_out_toggle(d7);
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gpio_out_toggle(e);
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}
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// Transmit 8 bits to the chip
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static void
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hd44780_xmit_byte(struct hd44780 *h, uint8_t data)
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{
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struct gpio_out e = h->e, d4 = h->d4, d5 = h->d5, d6 = h->d6, d7 = h->d7;
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hd44780_xmit_bits(h->last ^ data, e, d4, d5, d6, d7);
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h->last = data << 4;
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hd44780_xmit_bits(data ^ h->last, e, d4, d5, d6, d7);
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}
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// Transmit a series of bytes to the chip
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static void
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hd44780_xmit(struct hd44780 *h, uint8_t len, uint8_t *data)
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{
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uint32_t last_cmd_time=h->last_cmd_time, cmd_wait_ticks=h->cmd_wait_ticks;
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while (len--) {
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uint8_t b = *data++;
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while (timer_read_time() - last_cmd_time < cmd_wait_ticks)
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irq_poll();
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hd44780_xmit_byte(h, b);
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last_cmd_time = timer_read_time();
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}
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h->last_cmd_time = last_cmd_time;
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}
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/****************************************************************
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* Interface
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****************************************************************/
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void
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command_config_hd44780(uint32_t *args)
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{
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struct hd44780 *h = oid_alloc(args[0], command_config_hd44780, sizeof(*h));
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h->rs = gpio_out_setup(args[1], 0);
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h->e = gpio_out_setup(args[2], 0);
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h->d4 = gpio_out_setup(args[3], 0);
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h->d5 = gpio_out_setup(args[4], 0);
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h->d6 = gpio_out_setup(args[5], 0);
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h->d7 = gpio_out_setup(args[6], 0);
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// Calibrate cmd_wait_ticks
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irq_disable();
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uint32_t start = timer_read_time();
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hd44780_xmit_byte(h, 0);
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uint32_t end = timer_read_time();
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irq_enable();
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uint32_t diff = end - start, delay_ticks = args[7];
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if (delay_ticks > diff)
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h->cmd_wait_ticks = delay_ticks - diff;
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}
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DECL_COMMAND(command_config_hd44780,
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"config_hd44780 oid=%c rs_pin=%u e_pin=%u"
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" d4_pin=%u d5_pin=%u d6_pin=%u d7_pin=%u delay_ticks=%u");
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void
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command_hd44780_send_cmds(uint32_t *args)
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{
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struct hd44780 *h = oid_lookup(args[0], command_config_hd44780);
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gpio_out_write(h->rs, 0);
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uint8_t len = args[1], *cmds = (void*)(size_t)args[2];
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hd44780_xmit(h, len, cmds);
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}
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DECL_COMMAND(command_hd44780_send_cmds, "hd44780_send_cmds oid=%c cmds=%*s");
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void
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command_hd44780_send_data(uint32_t *args)
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{
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struct hd44780 *h = oid_lookup(args[0], command_config_hd44780);
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gpio_out_write(h->rs, 1);
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uint8_t len = args[1], *data = (void*)(size_t)args[2];
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hd44780_xmit(h, len, data);
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}
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DECL_COMMAND(command_hd44780_send_data, "hd44780_send_data oid=%c data=%*s");
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void
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hd44780_shutdown(void)
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{
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uint8_t i;
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struct hd44780 *h;
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foreach_oid(i, h, command_config_hd44780) {
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gpio_out_write(h->rs, 0);
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gpio_out_write(h->e, 0);
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gpio_out_write(h->d4, 0);
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gpio_out_write(h->d5, 0);
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gpio_out_write(h->d6, 0);
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gpio_out_write(h->d7, 0);
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h->last = 0;
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}
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}
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DECL_SHUTDOWN(hd44780_shutdown);
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