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swuart/: use a hardware timer and allow full-duplex operation
This commit is contained in:
Werner Almesberger
parent
4689882497
commit
8816dcfa3c
@ -1,5 +1,5 @@
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CC = mipsel-openwrt-linux-gcc
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CFLAGS = -g -Wall -I../libubb/include
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CFLAGS = -g -Wall -O9 -I../libubb/include
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LDFLAGS = -static
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LDLIBS = -L../libubb -lubb
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259
swuart/swuart.c
259
swuart/swuart.c
@ -1,5 +1,5 @@
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/*
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* swuart/swuart.c - Software-implemented half-duplex UART for UBB
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* swuart/swuart.c - Software-implemented UART for UBB
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*
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* Written 2012 by Werner Almesberger
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* Copyright 2012 Werner Almesberger
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@ -11,38 +11,221 @@
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*/
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#include <stdbool.h>
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#include <stdlib.h>
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#include <stdio.h>
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#include <unistd.h>
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#include <string.h>
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#include <ubb/ubb.h>
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#include <ubb/regs4740.h>
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#define TX UBB_DAT2
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#define RX UBB_DAT0
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#define TX UBB_DAT1
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#define TIMER 7
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static uint32_t tx_mask, rx_mask;
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static int loops;
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static uint32_t ticks;
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/* ----- Hardware timer ---------------------------------------------------- */
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/*
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* TX bit timing:
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*
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* bps loops nominal estimated measured error
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* 1152200 202 8.696 us 8.673 us 8.67 us -0.3%
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* 38400 619 26.042 us 26.062 us 26.04 us n/a
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* 9600 2494 104.167 us 104.250 us 104.16 us n/a
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*
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* Estimated loop timing: 0.25+0.0417*loops
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* We run the hardware timer at PCLK/16 = 7 MHz. This gives us 60 cycles at
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* 115200 bps and sets the lowest data rate to 106.8 bps.
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*/
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#define PCLK (112*1000*1000) /* 112 MHz */
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#define TCLK (PCLK/16) /* 7 MHz */
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static void get_timer(uint32_t cycle)
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{
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TSCR = 1 << TIMER; /* enable clock to timer */
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TDFR(TIMER) = cycle-1; /* cycle = one bit time */
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TCSR(TIMER) = (2 << 3) | 1; /* count at PCLK/16 */
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}
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static void reset_timer(void)
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{
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TECR = 1 << TIMER; /* disable timer */
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TCNT(TIMER) = 0; /* reset timer */
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TFCR = 0x10001 << TIMER; /* clear flags */
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TESR = 1 << TIMER; /* enable timer */
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}
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static void set_half_cycle(uint32_t cycle)
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{
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uint32_t t;
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t = (uint16_t) TCNT(TIMER)+(cycle >> 1);
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/* TCNT+cycle/2 mod cycle-1 */
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if (t >= cycle-1)
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t -= cycle-1;
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TDHR(TIMER) = t;
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TFCR = 0x10000 << TIMER; /* clear half flags */
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}
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static void release_timer(void)
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{
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TECR = 1 << TIMER; /* disable timer */
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TFCR = 0x10001 << TIMER; /* clear flags */
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TSSR = 1 << TIMER; /* disable clock to timer */
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}
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static inline bool timer_full(void)
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{
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if (!(TFR & (1 << TIMER)))
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return 0;
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TFCR = 1 << TIMER;
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return 1;
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}
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static inline bool timer_half(void)
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{
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if (!(TFR & (0x10000 << TIMER)))
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return 0;
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TFCR = 0x10000 << TIMER;
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return 1;
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}
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/* ----- Enable/disable interrupts ----------------------------------------- */
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static uint32_t old_icmr;
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static void disable_interrupts(void)
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{
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old_icmr = ICMR;
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ICMSR = 0xffffffff;
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}
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static void enable_interrupts(void)
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{
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ICMCR = ~old_icmr;
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}
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/* ----- Transmit a block -------------------------------------------------- */
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struct rx_err {
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unsigned glitch; /* unstable start bit */
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unsigned framing; /* stop bit wasn't "1" */
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unsigned overflow; /* buffer overflow */
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} rx_err;
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static int trx(uint8_t *out, int out_size, uint8_t *in, int in_size,
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unsigned wait_bits, unsigned idle_bits)
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{
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unsigned tx, rx = 0, idle = 0;
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int tx_bits = 0, rx_bits = 0;
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int in_len = 0;
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reset_timer();
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while (1) {
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full:
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/* timer has just crossed FULL */
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if (tx_bits) {
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if (tx & 1)
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SET(tx_mask);
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else
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CLR(tx_mask);
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tx >>= 1;
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tx_bits--;
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} else {
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if (out_size) {
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CLR(tx_mask);
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tx = *out++ | 0x100;
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out_size--;
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tx_bits = 9;
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} else {
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if (idle++ == wait_bits)
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return in_len;
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}
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}
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/* wait for reception (if any) */
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if (rx_bits) {
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while (!timer_half());
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} else {
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while (!timer_full())
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if (!PIN(rx_mask)) {
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set_half_cycle(ticks);
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rx_bits = 10;
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break;
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}
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if (!rx_bits)
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continue;
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while (!timer_half())
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if (timer_full())
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goto full;
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}
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/* timer has just crossed HALF */
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rx = (rx >> 1) | (PIN(rx_mask) ? 0x200 : 0);
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if (!--rx_bits) {
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if (rx & 1) {
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rx_err.glitch++;
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} else if (!(rx & 0x200)) {
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rx_err.framing++;
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} else if (in_len == in_size) {
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rx_err.overflow++;
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} else {
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*in++ = rx >> 1;
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in_len++;
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idle = 0;
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wait_bits = idle_bits;
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}
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}
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while (!timer_full());
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}
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}
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int swuart_trx(void *out, int out_size, void *in, int in_size,
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int wait_bits, int idle_bits)
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{
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int got;
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disable_interrupts();
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get_timer(ticks);
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got = trx(out, out_size, in, in_size, wait_bits, idle_bits);
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release_timer();
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enable_interrupts();
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return got;
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}
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/* ----- Open/close the software UART -------------------------------------- */
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int swuart_open(uint32_t tx, uint32_t rx, int bps)
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{
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if (ubb_open(0))
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return -1;
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loops = 24000000/bps-6;
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ticks = TCLK/bps-1;
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tx_mask = tx;
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rx_mask = rx;
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@ -55,47 +238,39 @@ int swuart_open(uint32_t tx, uint32_t rx, int bps)
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}
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static void send(uint8_t *out, int out_size)
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void swuart_close(void)
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{
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const uint8_t *end = out+out_size;
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unsigned pattern;
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int i, j;
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while (out != end) {
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pattern = 0x200 | (*out++ << 1);
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for (i = 0; i != 10; i++) {
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if (pattern & 1)
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SET(tx_mask);
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else
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CLR(tx_mask);
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pattern >>= 1;
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for (j = 0; j != loops; j++);
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}
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}
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ubb_close(0);
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}
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int swuart_trx(void *out, int out_size, void *in, int in_size, int bit_wait)
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/* ----- Main -------------------------------------------------------------- */
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static void at_exit(void)
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{
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uint32_t icmr;
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icmr = ICMR;
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ICMSR = 0xffffffff;
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send(out, out_size);
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ICMCR = ~icmr;
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return 0;
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swuart_close();
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}
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int main(int argc, char **argv)
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{
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swuart_open(TX, 0, atoi(argv[1]));
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uint8_t buf[40];
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int got, i;
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swuart_open(TX, RX, atoi(argv[1]));
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atexit(at_exit);
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while (1) {
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swuart_trx("U ", 2, NULL, 0, 0);
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got = swuart_trx(argv[2], strlen(argv[2]), buf, sizeof(buf),
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10000, 100);
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printf("%d (%d %d %d): ", got,
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rx_err.glitch, rx_err.framing, rx_err.overflow);
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for (i = 0; i != got; i++)
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if (buf[i] >= ' ' && buf[i] <= '~')
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printf("%c", buf[i]);
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else
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printf("\\%02o", buf[i]);
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printf("\n");
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usleep(100);
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}
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ubb_close(0);
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}
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