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// Commands for sending messages to an st7920 lcd driver
//
// Copyright (C) 2018 Kevin O'Connor <kevin@koconnor.net>
//
// This file may be distributed under the terms of the GNU GPLv3 license.
#include "autoconf.h" // CONFIG_MACH_AVR
#include "basecmd.h" // oid_alloc
#include "board/gpio.h" // gpio_out_write
#include "board/irq.h" // irq_poll
#include "board/misc.h" // timer_from_us
#include "command.h" // DECL_COMMAND
#include "sched.h" // DECL_SHUTDOWN
struct st7920 {
uint32_t last_cmd_time, sync_wait_ticks, cmd_wait_ticks;
struct gpio_out sclk, sid;
};
/****************************************************************
* Transmit functions
****************************************************************/
static uint32_t
nsecs_to_ticks(uint32_t ns)
{
return timer_from_us(ns * 1000) / 1000000;
}
static inline void
ndelay(uint32_t nsecs)
{
if (CONFIG_MACH_AVR)
// Slower MCUs don't require a delay
return;
uint32_t end = timer_read_time() + nsecs_to_ticks(nsecs);
while (timer_is_before(timer_read_time(), end))
irq_poll();
}
#define SYNC_CMD 0xf8
#define SYNC_DATA 0xfa
// Write eight bits to the st7920 via the serial interface
static void
st7920_xmit_byte(struct st7920 *s, uint8_t data)
{
struct gpio_out sclk = s->sclk, sid = s->sid;
uint8_t i;
for (i=0; i<8; i++) {
if (data & 0x80) {
gpio_out_toggle(sid);
data = ~data;
}
ndelay(200);
gpio_out_toggle(sclk);
ndelay(200);
data <<= 1;
gpio_out_toggle(sclk);
}
}
// Transmit a series of command bytes to the chip
static void
st7920_xmit(struct st7920 *s, uint8_t count, uint8_t *cmds)
{
if (!count)
return;
// Send first byte (with longer delay)
uint32_t last_cmd_time = s->last_cmd_time, wait_ticks = s->sync_wait_ticks;
uint8_t cmd = *cmds++;
st7920_xmit_byte(s, cmd & 0xf0);
while (timer_read_time() - last_cmd_time < wait_ticks)
// Can't complete transfer until delay complete
irq_poll();
st7920_xmit_byte(s, cmd << 4);
last_cmd_time = timer_read_time();
// Send subsequent bytes
wait_ticks = s->cmd_wait_ticks;
while (--count) {
uint8_t cmd = *cmds++;
st7920_xmit_byte(s, cmd & 0xf0);
while (timer_read_time() - last_cmd_time < wait_ticks)
// Can't complete transfer until delay complete
irq_poll();
st7920_xmit_byte(s, cmd << 4);
last_cmd_time = timer_read_time();
}
s->last_cmd_time = last_cmd_time;
}
/****************************************************************
* Interface
****************************************************************/
void
command_config_st7920(uint32_t *args)
{
struct st7920 *s = oid_alloc(args[0], command_config_st7920, sizeof(*s));
s->sclk = gpio_out_setup(args[2], 0);
s->sid = gpio_out_setup(args[3], 0);
gpio_out_setup(args[1], 1);
if (!CONFIG_HAVE_STRICT_TIMING) {
s->sync_wait_ticks = args[4];
s->cmd_wait_ticks = args[5];
return;
}
// Calibrate cmd_wait_ticks
st7920_xmit_byte(s, SYNC_CMD);
st7920_xmit_byte(s, 0x20);
irq_disable();
uint32_t start = timer_read_time();
st7920_xmit_byte(s, 0x00);
uint32_t end = timer_read_time();
irq_enable();
s->last_cmd_time = end;
uint32_t diff = end - start, sync_delay_ticks = args[4];
if (sync_delay_ticks > diff)
s->sync_wait_ticks = sync_delay_ticks - diff;
uint32_t cmd_delay_ticks = args[5];
if (cmd_delay_ticks > diff)
s->cmd_wait_ticks = cmd_delay_ticks - diff;
}
DECL_COMMAND(command_config_st7920,
"config_st7920 oid=%c cs_pin=%u sclk_pin=%u sid_pin=%u"
" sync_delay_ticks=%u cmd_delay_ticks=%u");
void
command_st7920_send_cmds(uint32_t *args)
{
struct st7920 *s = oid_lookup(args[0], command_config_st7920);
st7920_xmit_byte(s, SYNC_CMD);
uint8_t len = args[1], *cmds = command_decode_ptr(args[2]);
st7920_xmit(s, len, cmds);
}
DECL_COMMAND(command_st7920_send_cmds, "st7920_send_cmds oid=%c cmds=%*s");
void
command_st7920_send_data(uint32_t *args)
{
struct st7920 *s = oid_lookup(args[0], command_config_st7920);
st7920_xmit_byte(s, SYNC_DATA);
uint8_t len = args[1], *data = command_decode_ptr(args[2]);
st7920_xmit(s, len, data);
}
DECL_COMMAND(command_st7920_send_data, "st7920_send_data oid=%c data=%*s");
void
st7920_shutdown(void)
{
uint8_t i;
struct st7920 *s;
foreach_oid(i, s, command_config_st7920) {
gpio_out_write(s->sclk, 0);
gpio_out_write(s->sid, 0);
}
}
DECL_SHUTDOWN(st7920_shutdown);
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