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Improve optimistic_yield intervals for performance gain in sketches #7952

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Improve optimistic_yield intervals for performance gain in sketches #7952

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041d2bb
Conservative adjustment of optimistic_yield intervals.
dok-net Mar 31, 2021
671a967
Review provided rationale for original interval value.
dok-net Mar 31, 2021
3cb53ba
More frequent optimistic_yield looks safe to me here.
dok-net Apr 8, 2021
f964600
Optimistic_yield interval changes from PR #7832, these need intense r…
dok-net Apr 8, 2021
07566e4
Wire has an available() function - 10000µs optimistic_yield interval …
dok-net Apr 9, 2021
d3bf7f9
Per review by @earlephilhower
dok-net Apr 11, 2021
342c94e
Refactor macro to an inline function
dok-net May 16, 2021
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31 changes: 22 additions & 9 deletions cores/esp8266/core_esp8266_wiring_pulse.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -26,13 +26,20 @@ extern "C" {

extern uint32_t xthal_get_ccount();

#define WAIT_FOR_PIN_STATE(state) \
while (digitalRead(pin) != (state)) { \
if (xthal_get_ccount() - start_cycle_count > timeout_cycles) { \
return 0; \
} \
optimistic_yield(5000); \
namespace {
inline __attribute__((always_inline)) bool waitForPinState(
const uint8_t pin, const uint8_t state,
const uint32_t timeout_cycles, const uint32_t start_cycle_count)
{
while (digitalRead(pin) != state) {
if (xthal_get_ccount() - start_cycle_count > timeout_cycles) {
return false;
}
optimistic_yield(1000);
}
return true;
}
}

// max timeout is 27 seconds at 160MHz clock and 54 seconds at 80MHz clock
unsigned long pulseIn(uint8_t pin, uint8_t state, unsigned long timeout)
Expand All @@ -43,10 +50,16 @@ unsigned long pulseIn(uint8_t pin, uint8_t state, unsigned long timeout)
}
const uint32_t timeout_cycles = microsecondsToClockCycles(timeout);
const uint32_t start_cycle_count = xthal_get_ccount();
WAIT_FOR_PIN_STATE(!state);
WAIT_FOR_PIN_STATE(state);
if (!waitForPinState(pin, !state, timeout_cycles, start_cycle_count)) {
return 0;
}
if (!waitForPinState(pin, state, timeout_cycles, start_cycle_count)) {
return 0;
}
const uint32_t pulse_start_cycle_count = xthal_get_ccount();
WAIT_FOR_PIN_STATE(!state);
if (!waitForPinState(pin, !state, timeout_cycles, start_cycle_count)) {
return 0;
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This is wrong per my reading of the (not so hot docs) https://www.arduino.cc/reference/en/language/functions/advanced-io/pulsein/?setlang=it

Return 0 on no pulse beginning edge detected. OTW, it should return the full timeout as the pulse width (i.e. get rid of the return 0 and just fallthru tho the return below).

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@earlephilhower I thought I had answered a long time before. IIRC I researched and besides this refactoring not changing how the return works before, my reading of the docs etc was that returning 0 was and is correct. Hm.

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@earlephilhower Can you agree this year; the change is just same effective execution path as with the macros before?

}
return clockCyclesToMicroseconds(xthal_get_ccount() - pulse_start_cycle_count);
}

Expand Down
6 changes: 4 additions & 2 deletions cores/esp8266/uart.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -510,7 +510,10 @@ uart_tx_fifo_full(const int uart_nr)
static void
uart_do_write_char(const int uart_nr, char c)
{
while(uart_tx_fifo_full(uart_nr));
while(uart_tx_fifo_full(uart_nr))
{
optimistic_yield(10000UL);
}

USF(uart_nr) = c;
}
Expand Down Expand Up @@ -544,7 +547,6 @@ uart_write(uart_t* uart, const char* buf, size_t size)
const int uart_nr = uart->uart_nr;
while (size--) {
uart_do_write_char(uart_nr, pgm_read_byte(buf++));
optimistic_yield(10000UL);
}

return ret;
Expand Down
4 changes: 2 additions & 2 deletions libraries/ESP8266WiFi/src/WiFiUdp.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -117,7 +117,7 @@ int WiFiUDP::available() {
if (!result) {
// yielding here will not make more data "available",
// but it will prevent the system from going into WDT reset
optimistic_yield(1000);
optimistic_yield(100UL);
}

return result;
Expand Down Expand Up @@ -194,7 +194,7 @@ int WiFiUDP::parsePacket()
return 0;

if (!_ctx->next()) {
optimistic_yield(100);
optimistic_yield(100UL);
return 0;
}

Expand Down
2 changes: 1 addition & 1 deletion libraries/Wire/Wire.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -227,7 +227,7 @@ int TwoWire::available(void)
{
// yielding here will not make more data "available",
// but it will prevent the system from going into WDT reset
optimistic_yield(1000);
optimistic_yield(100UL);
}

return result;
Expand Down