swuart/: merge library part into libubb

libubb/Makefile

@@ -17,8 +17,8 @@ CC = $(TARGET)gcc
 CFLAGS = -g -Wall -Iinclude
 LIB = libubb.a
 
-OBJS = ubb.o
-HDRS = ubb/ubb.h ubb/regbase.h ubb/regs4740.h
+OBJS = ubb.o swuart.o
+HDRS = ubb/ubb.h ubb/regbase.h ubb/regs4740.h ubb/swuart.h
 
 .PHONY:		all clean spotless
 

libubb/include/ubb/swuart.h

@@ -0,0 +1,35 @@
+/*
+ * include/ubb/swuart.h - Software-implemented UART for UBB
+ *
+ * Written 2012 by Werner Almesberger
+ * Copyright 2012 Werner Almesberger
+ *
+ * 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 2 of the License, or
+ * (at your option) any later version.
+ */
+
+#ifndef UBB_SWUART_H
+#define UBB_SWUART_H
+
+#include <stdint.h>
+
+
+struct swuart_err {
+	unsigned glitch;	/* unstable start bit */
+	unsigned framing;	/* stop bit wasn't "1" */
+	unsigned overflow;	/* buffer overflow */
+};
+
+
+int swuart_trx(void *out, int out_size, void *in, int in_size,
+    int wait_bits, int idle_bits);
+
+unsigned swuart_get_errors(struct swuart_err *res);
+void swuart_clear_errors(void);
+
+int swuart_open(uint32_t tx, uint32_t rx, int bps);
+void swuart_close(void);
+
+#endif /* !UBB_SWUART_H */

libubb/swuart.c

@@ -0,0 +1,254 @@
+/*
+ * swuart/swuart.c - Software-implemented UART for UBB
+ *
+ * Written 2012 by Werner Almesberger
+ * Copyright 2012 Werner Almesberger
+ *
+ * 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 2 of the License, or
+ * (at your option) any later version.
+ */
+
+
+#include <stdbool.h>
+#include <string.h>
+
+#include <ubb/ubb.h>
+#include <ubb/regs4740.h>
+#include <ubb/swuart.h>
+
+
+#define	TIMER	7
+
+
+static uint32_t tx_mask, rx_mask;
+static uint32_t ticks;
+
+
+/* ----- Hardware timer ---------------------------------------------------- */
+
+
+/*
+ * We run the hardware timer at PCLK/16 = 7 MHz. This gives us 60 cycles at
+ * 115200 bps and sets the lowest data rate to 106.8 bps.
+ */
+
+#define	PCLK	(112*1000*1000)		/* 112 MHz */
+#define	TCLK	(PCLK/16)		/*   7 MHz */
+
+
+static void get_timer(uint32_t cycle)
+{
+	TSCR = 1 << TIMER;		/* enable clock to timer */
+	TDFR(TIMER) = cycle-1;		/* cycle = one bit time */
+	TCSR(TIMER) = (2 << 3) | 1;	/* count at PCLK/16 */
+}
+
+
+static void reset_timer(void)
+{
+	TECR = 1 << TIMER;		/* disable timer */
+	TCNT(TIMER) = 0;		/* reset timer */
+	TFCR = 0x10001 << TIMER;	/* clear flags */
+	TESR = 1 << TIMER;		/* enable timer */
+}
+
+
+static void set_half_cycle(uint32_t cycle)
+{
+	uint32_t t;
+
+	t = (uint16_t) TCNT(TIMER)+(cycle >> 1);
+					/* TCNT+cycle/2 mod cycle-1 */
+	if (t >= cycle-1)
+		t -= cycle-1;
+	TDHR(TIMER) = t;
+	TFCR = 0x10000 << TIMER;		/* clear half flags */
+}
+
+
+static void release_timer(void)
+{
+	TECR = 1 << TIMER;		/* disable timer */
+	TFCR = 0x10001 << TIMER;	/* clear flags */
+	TSSR = 1 << TIMER;		/* disable clock to timer */
+}
+
+
+static inline bool timer_full(void)
+{
+	if (!(TFR & (1 << TIMER)))
+		return 0;
+	TFCR = 1 << TIMER;
+	return 1;
+}
+
+
+static inline bool timer_half(void)
+{
+	if (!(TFR & (0x10000 << TIMER)))
+		return 0;
+	TFCR = 0x10000 << TIMER;
+	return 1;
+}
+
+
+/* ----- Enable/disable interrupts ----------------------------------------- */
+
+
+static uint32_t old_icmr;
+
+
+static void disable_interrupts(void)
+{
+	old_icmr = ICMR;
+	ICMSR = 0xffffffff;
+}
+
+
+static void enable_interrupts(void)
+{
+	ICMCR = ~old_icmr;
+}
+
+
+/* ----- Transmit a block -------------------------------------------------- */
+
+
+static struct swuart_err errors;
+
+
+static int trx(uint8_t *out, int out_size, uint8_t *in, int in_size,
+    unsigned wait_bits, unsigned idle_bits)
+{
+	unsigned tx, rx = 0, idle = 0;
+	int tx_bits = 0, rx_bits = 0;
+	int in_len = 0;
+
+	reset_timer();
+	while (1) {
+full:
+		/* timer has just crossed FULL */
+
+		if (tx_bits) {
+			if (tx & 1)
+				SET(tx_mask);
+			else
+				CLR(tx_mask);
+			tx >>= 1;
+			tx_bits--;
+		} else {
+			if (out_size) {
+				CLR(tx_mask);
+				tx = *out++ | 0x100;
+				out_size--;
+				tx_bits = 9;
+			} else  {
+				if (idle++ == wait_bits)
+					return in_len;
+			}
+		}
+
+		/* wait for reception (if any) */
+
+		if (rx_bits) {
+			while (!timer_half());
+		} else {
+			while (!timer_full())
+				if (!PIN(rx_mask)) {
+					set_half_cycle(ticks);
+					rx_bits = 10;
+					break;
+				}
+			if (!rx_bits)
+				continue;
+			while (!timer_half())
+				if (timer_full())
+					goto full;
+		}
+
+		/* timer has just crossed HALF */
+
+		rx = (rx >> 1) | (PIN(rx_mask) ? 0x200 : 0);
+		if (!--rx_bits) {
+			if (rx & 1) {
+				errors.glitch++;
+			} else if (!(rx & 0x200)) {
+				errors.framing++;
+			} else if (in_len == in_size) {
+				errors.overflow++;
+			} else {
+				*in++ = rx >> 1;
+				in_len++;
+				idle = 0;
+				wait_bits = idle_bits;
+			}
+		}
+
+		while (!timer_full());
+	}
+}
+
+
+int swuart_trx(void *out, int out_size, void *in, int in_size,
+    int wait_bits, int idle_bits)
+{
+	int got;
+
+	disable_interrupts();
+	get_timer(ticks);
+
+	got = trx(out, out_size, in, in_size, wait_bits, idle_bits);
+
+	release_timer();
+	enable_interrupts();
+
+	return got;
+}
+
+
+/* ----- Access error counters --------------------------------------------- */
+
+
+unsigned swuart_get_errors(struct swuart_err *res)
+{
+	unsigned sum = errors.glitch+errors.framing+errors.overflow;
+
+	if (res)
+		*res = errors;
+	return sum;
+}
+
+
+void swuart_clear_errors(void)
+{
+	memset(&errors, 0, sizeof(errors));
+}
+
+
+/* ----- Open/close the software UART -------------------------------------- */
+
+
+int swuart_open(uint32_t tx, uint32_t rx, int bps)
+{
+	if (ubb_open(0))
+		return -1;
+
+	ticks = TCLK/bps-1;
+	tx_mask = tx;
+	rx_mask = rx;
+
+	ubb_power(1);
+	OUT(tx);
+	CLR(tx);
+	IN(rx);
+
+	return 0;
+}
+
+
+void swuart_close(void)
+{
+	ubb_close(0);
+}