From 63cbb8facd9d9dc016f902bb312283f0b5f8d055 Mon Sep 17 00:00:00 2001
From: Daniel Friesel <derf@finalrewind.org>
Date: Fri, 26 Oct 2018 08:58:18 +0200
Subject: [PATCH] Merge SoftI2C timer={0,1} code paths, adjust timing according
to I2C spec
It's occasionally slower than specified, but should never be too fast
---
src/arch/msp430fr5969lp/arch.cc | 10 +-
src/driver/soft_i2c.cc | 184 +++++---------------------------
2 files changed, 33 insertions(+), 161 deletions(-)
diff --git a/src/arch/msp430fr5969lp/arch.cc b/src/arch/msp430fr5969lp/arch.cc
index cde0503..1eb34b5 100644
--- a/src/arch/msp430fr5969lp/arch.cc
+++ b/src/arch/msp430fr5969lp/arch.cc
@@ -104,8 +104,14 @@ volatile char run_loop = 0;
void Arch::delay_us(unsigned int const us)
{
- for (unsigned int i = 0; i < us/10; i++) {
- __delay_cycles(F_CPU / 100000UL);
+ if (us < 10) {
+ for (unsigned int i = 0; i < us; i++) {
+ __delay_cycles(F_CPU / 1000000UL);
+ }
+ } else {
+ for (unsigned int i = 0; i < us/10; i++) {
+ __delay_cycles(F_CPU / 100000UL);
+ }
}
}
void Arch::delay_ms(unsigned int const ms)
diff --git a/src/driver/soft_i2c.cc b/src/driver/soft_i2c.cc
index 3679514..6c36b6f 100644
--- a/src/driver/soft_i2c.cc
+++ b/src/driver/soft_i2c.cc
@@ -11,6 +11,7 @@
#error "SOFTI2C_TIMER and TIMER_CYCLES are mutually exclusive"
#endif
#include "driver/timer.h"
+volatile unsigned char timer_done = 0;
#endif
#ifdef SOFTI2C_PULLUP_INTERNAL
@@ -30,171 +31,33 @@
#define SCL_LOW gpio.output(scl)
#endif /* SOFTI2C_PULLUP */
-#ifndef SOFTI2C_TIMER
-
-#if F_I2C < 50000
-#define I2C_WAIT arch.delay_us((500000UL / F_I2C) - 10)
-#else
-#define I2C_WAIT
-#endif /* !SOFTI2C_TIMER */
-
-signed char SoftI2C::setup()
-{
-#ifdef SOFTI2C_PULLUP_EXTERNAL
- gpio.output(sda_pull);
- gpio.output(scl_pull);
-#endif
-#ifdef SOFTI2C_PULLUP_FIXED_GPIO
-#if MULTIPASS_ARCH_msp430fr5969lp
- gpio.output(GPIO::p1_4, 1);
- gpio.output(GPIO::p1_5, 1);
-#else
-#error "softi2c_pullup=gpio not supported on this architecture"
-#endif /* MULTIPASS_ARCH_* */
-#endif /* SOFTI2C_PULLUP_FIXED_GPIO */
- SDA_HIGH;
- SCL_HIGH;
- return 0;
-}
-
-void SoftI2C::start()
-{
- SDA_HIGH;
- SCL_HIGH;
- I2C_WAIT;
- SDA_LOW;
- I2C_WAIT;
- SCL_LOW;
-}
-
-void SoftI2C::stop()
-{
- SCL_LOW;
- I2C_WAIT;
- SDA_LOW;
- I2C_WAIT;
- SCL_HIGH;
- I2C_WAIT;
- SDA_HIGH;
-}
-
-bool SoftI2C::tx(unsigned char byte)
-{
- unsigned char got_ack = 0;
- for (unsigned char i = 0; i <= 8; i++) {
- if ((byte & 0x80) || (i == 8)) {
- SDA_HIGH;
- } else {
- SDA_LOW;
- }
- byte <<= 1;
- I2C_WAIT;
- SCL_HIGH;
- while (!gpio.read(scl)) ;
- I2C_WAIT;
- if (i == 8) {
- if (!gpio.read(sda)) {
- got_ack = 1;
- }
- }
- SCL_LOW;
- I2C_WAIT;
- }
- return got_ack;
-}
-
-unsigned char SoftI2C::rx(bool send_ack)
-{
- unsigned char byte = 0;
- SDA_HIGH;
- for (unsigned char i = 0; i <= 8; i++) {
- I2C_WAIT;
- SCL_HIGH;
- while (!gpio.read(scl)) ;
- I2C_WAIT;
- if ((i < 8) && gpio.read(sda)) {
- byte |= 1 << (7 - i);
- }
- I2C_WAIT;
- SCL_LOW;
- I2C_WAIT;
- if ((i == 7) && send_ack) {
- SDA_LOW;
- } else if ((i == 8) && send_ack) {
- SDA_HIGH;
- }
- }
- return byte;
-}
-
-void SoftI2C::scan(unsigned int *results)
-{
- unsigned char i2caddr;
- for (unsigned char address = 0; address < 128; address++) {
-
- i2caddr = (address << 1) | 0;
- start();
-
- if (tx(i2caddr)) {
- results[address / (8 * sizeof(unsigned int))] |= 1 << (address % (8 * sizeof(unsigned int)));
- stop();
- }
- }
- stop();
-}
-
-signed char SoftI2C::xmit(unsigned char address,
- unsigned char tx_len, unsigned char *tx_buf,
- unsigned char rx_len, unsigned char *rx_buf)
+inline void i2c_wait()
{
- unsigned char i;
-
- if (tx_len) {
- start();
- tx((address << 1) | 0);
-
- for (i = 0; i < tx_len; i++) {
- tx(tx_buf[i]);
- }
- }
- if (rx_len) {
- start();
- tx((address << 1) | 1);
-
- for (i = 1; i <= rx_len; i++) {
- rx_buf[i-1] = rx((i < rx_len) * 1);
- }
- }
-
- stop();
-
- return 0;
-}
-
-#else
-
-volatile unsigned char timer_done = 0;
-
+#ifdef SOFTI2C_TIMER
/*
- * Note: On MSP430, if F_CPU / F_I2C < 60 (approx.), await_timer() does not
+ * Note: On MSP430, if F_CPU / F_I2C < 60 (approx.), i2c_wait() does not
* work. Probably related to missed interrupts / not enough cycles between
* start and idle? We work around this for now by simulating an immediate
* return in these cases.
*/
#if MULTIPASS_ARCH_msp430fr5969lp && ((F_CPU / F_I2C) < 60)
-inline void await_timer() {}
#else
-inline void await_timer()
-{
timer_done = 0;
timer.start(1);
while (!timer_done) {
arch.idle();
}
timer.stop();
-}
#endif
+#else /* !SOFTI2C_TIMER */
+#if (500000UL / F_I2C) > 11
+ arch.delay_us((500000UL / F_I2C) - 10);
+#else
+ arch.delay_us(500000UL / F_I2C);
+#endif
+#endif /* SOFTI2C_TIMER */
+}
signed char SoftI2C::setup()
{
@@ -212,6 +75,7 @@ signed char SoftI2C::setup()
#endif /* SOFTI2C_PULLUP_FIXED_GPIO */
SDA_HIGH;
SCL_HIGH;
+#ifdef SOFTI2C_TIMER
/*
* I2C frequency is the time between two SCL low->high transitions
* (or high->low, whatever you prefer). For the timer, we need to set the
@@ -221,6 +85,7 @@ signed char SoftI2C::setup()
* Timer Freq [kHz] = I2C Freq [Hz] * 2 / 1000
*/
timer.setup_khz(F_I2C / 500);
+#endif
return 0;
}
@@ -228,21 +93,22 @@ void SoftI2C::start()
{
SDA_HIGH;
SCL_HIGH;
- await_timer();
+ i2c_wait(); // t_{SU,STA} >= 4.7 µs (für Sr)
SDA_LOW;
- await_timer();
+ i2c_wait(); // t_{HD,STA} >= 4 µs
SCL_LOW;
- await_timer();
+ i2c_wait();
}
void SoftI2C::stop()
{
SCL_LOW;
SDA_LOW;
- await_timer();
+ i2c_wait();
SCL_HIGH;
- await_timer();
+ i2c_wait(); // t_{SU,STO} >= 4 µs
SDA_HIGH;
+ i2c_wait(); // t_{BUF} >= 4.7 µs
}
bool SoftI2C::tx(unsigned char byte)
@@ -255,8 +121,9 @@ bool SoftI2C::tx(unsigned char byte)
SDA_LOW;
}
byte <<= 1;
+ i2c_wait();
SCL_HIGH;
- await_timer();
+ i2c_wait();
while (!gpio.read(scl)) ;
if (i == 8) {
if (!gpio.read(sda)) {
@@ -264,7 +131,6 @@ bool SoftI2C::tx(unsigned char byte)
}
}
SCL_LOW;
- await_timer();
}
return got_ack;
}
@@ -274,14 +140,14 @@ unsigned char SoftI2C::rx(bool send_ack)
unsigned char byte = 0;
SDA_HIGH;
for (unsigned char i = 0; i <= 8; i++) {
+ i2c_wait();
SCL_HIGH;
- await_timer();
+ i2c_wait();
while (!gpio.read(scl)) ;
if ((i < 8) && gpio.read(sda)) {
byte |= 1 << (7 - i);
}
SCL_LOW;
- await_timer();
if ((i == 7) && send_ack) {
SDA_LOW;
} else if ((i == 8) && send_ack) {
@@ -336,10 +202,10 @@ signed char SoftI2C::xmit(unsigned char address,
return 0;
}
+#ifdef SOFTI2C_TIMER
ON_TIMER_INTERRUPT_head
timer_done = 1;
ON_TIMER_INTERRUPT_tail
-
#endif
#if SOFTI2C_PULLUP_EXTERNAL
--
GitLab