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Survive I2C slaves that stretch the clock #266

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Merged
lovyan03 merged 2 commits into from
Aug 24, 2026
Merged

Survive I2C slaves that stretch the clock #266

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6c37143
Wait for chunked ESP32 I2C reads to complete
ainyan03 Aug 24, 2026
90dc8db
Survive slaves that stretch the clock for milliseconds
ainyan03 Aug 24, 2026
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49 changes: 40 additions & 9 deletions src/lgfx/v1/platforms/esp32/common.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1654,6 +1654,11 @@ namespace lgfx
for (auto &bup : backup_pins) { bup.restore(); }
}

/// Minimum time a transfer may stall (clock stretching or a wedged bus)
/// before it is given up on; 25ms covers the SMBus Tlow:sext ceiling.
/// NACK handling does not depend on this limit.
static constexpr uint32_t i2c_stall_limit_us = 25000;

static cpp::result<void, error_t> i2c_wait(int i2c_port, bool flg_stop = false)
{
if (flg_stop == false && i2c_context[i2c_port].state.has_error()) { return cpp::fail(i2c_context[i2c_port].state.error()); }
Expand All @@ -1662,7 +1667,7 @@ namespace lgfx
auto dev = getDev(i2c_port);
typeof(dev->int_raw) int_raw;
int_raw.val = dev->int_raw.val; // ACK待ちステージをスキップした場合も後段の分岐で参照されるため必ず初期化する;
static constexpr uint32_t intmask = I2C_ACK_ERR_INT_RAW_M | I2C_END_DETECT_INT_RAW_M | I2C_ARBITRATION_LOST_INT_RAW_M;
static constexpr uint32_t intmask = I2C_ACK_ERR_INT_RAW_M | I2C_TIME_OUT_INT_RAW_M | I2C_END_DETECT_INT_RAW_M | I2C_ARBITRATION_LOST_INT_RAW_M;

if (i2c_context[i2c_port].wait_ack_stage)
{
Expand All @@ -1676,7 +1681,7 @@ namespace lgfx
#else
uint32_t us_limit = (dev->scl_high_period.period + dev->scl_low_period.period + 16 ) * (1 + dev->status_reg.tx_fifo_cnt);
#endif
us_limit += 512 << i2c_context[i2c_port].wait_ack_stage;
us_limit += i2c_stall_limit_us;

do
{
Expand All @@ -1688,6 +1693,13 @@ namespace lgfx
int_raw.val = dev->int_raw.val;

dev->int_clr.val = int_raw.val;
// A timeout or lost arbitration is fatal even when END is also set.
if (int_raw.val & (I2C_TIME_OUT_INT_RAW_M | I2C_ARBITRATION_LOST_INT_RAW_M))
{
res = cpp::fail(error_t::connection_lost);
i2c_context[i2c_port].state = cpp::fail(error_t::connection_lost);
}
else
#if !defined (CONFIG_IDF_TARGET) || defined (CONFIG_IDF_TARGET_ESP32)
if (!int_raw.end_detect || int_raw.ack_err)
#elif defined ( CONFIG_IDF_TARGET_ESP32C2 ) || defined ( CONFIG_IDF_TARGET_ESP32S3 ) || defined ( CONFIG_IDF_TARGET_ESP32C5 ) || defined ( CONFIG_IDF_TARGET_ESP32C6 ) || defined ( CONFIG_IDF_TARGET_ESP32C61 ) || defined ( CONFIG_IDF_TARGET_ESP32P4 ) || defined ( CONFIG_IDF_TARGET_ESP32H2 )
Expand Down Expand Up @@ -1721,22 +1733,37 @@ namespace lgfx
{
i2c_set_cmd(dev, 0, i2c_cmd_stop, 0);
i2c_set_cmd(dev, 1, i2c_cmd_end, 0);
static constexpr uint32_t intmask_ = I2C_ACK_ERR_INT_RAW_M | I2C_TIME_OUT_INT_RAW_M | I2C_END_DETECT_INT_RAW_M | I2C_ARBITRATION_LOST_INT_RAW_M | I2C_TRANS_COMPLETE_INT_RAW_M;
// Wake only on events that end the STOP; a NACK is evaluated after it completes.
static constexpr uint32_t intmask_ = I2C_TIME_OUT_INT_RAW_M | I2C_ARBITRATION_LOST_INT_RAW_M | I2C_TRANS_COMPLETE_INT_RAW_M;
updateDev(dev);
dev->int_clr.val = intmask_;
dev->int_clr.val = intmask_ | I2C_ACK_ERR_INT_RAW_M | I2C_END_DETECT_INT_RAW_M;
dev->ctr.trans_start = 1;
uint32_t ms = lgfx::millis();
taskYIELD();
while (!(dev->int_raw.val & intmask_) && ((millis() - ms) < 14));
while (!(dev->int_raw.val & intmask_) && ((millis() - ms) < (i2c_stall_limit_us / 1000))) { taskYIELD(); }
// A STOP that did not complete leaves the bus in an unknown state:
// recover it and refuse further use of this transaction.
{
uint32_t stop_raw = dev->int_raw.val;
if (res.has_value()
&& ((stop_raw & (I2C_TIME_OUT_INT_RAW_M | I2C_ARBITRATION_LOST_INT_RAW_M))
|| !(stop_raw & I2C_TRANS_COMPLETE_INT_RAW_M)))
{
res = cpp::fail(error_t::connection_lost);
i2c_context[i2c_port].state = cpp::fail(error_t::connection_lost);
i2c_stop(i2c_port);
}
}
#if !defined (CONFIG_IDF_TARGET) || defined (CONFIG_IDF_TARGET_ESP32)
if (res.has_value() && dev->int_raw.ack_err)
#elif defined ( CONFIG_IDF_TARGET_ESP32C2 ) || defined ( CONFIG_IDF_TARGET_ESP32S3 ) || defined ( CONFIG_IDF_TARGET_ESP32C5 ) || defined ( CONFIG_IDF_TARGET_ESP32C6 ) || defined ( CONFIG_IDF_TARGET_ESP32C61 ) || defined ( CONFIG_IDF_TARGET_ESP32P4 ) || defined ( CONFIG_IDF_TARGET_ESP32H2 )
if (res.has_value() && dev->int_raw.nack_int_raw)
#else
if (res.has_value() && dev->int_raw.nack)
#endif
{
{ // The STOP completed but a byte went unacknowledged.
res = cpp::fail(error_t::connection_lost);
i2c_context[i2c_port].state = cpp::fail(error_t::connection_lost);
}
//ESP_LOGI("LGFX", "I2C stop");
}
Expand Down Expand Up @@ -2143,11 +2170,14 @@ namespace lgfx
dev->ctr.fsm_rst = 1;
#endif

// SCL-low (clock stretch) watchdog. 2^21 source clocks stays past
// i2c_stall_limit_us on every supported source; the ESP32 register below is at
// its ceiling, about 13ms.
#if defined ( CONFIG_IDF_TARGET_ESP32C3 )
dev->timeout.time_out_value = 31;
dev->timeout.time_out_value = 21;
dev->timeout.time_out_en = 1;
#elif defined ( CONFIG_IDF_TARGET_ESP32C2 ) || defined ( CONFIG_IDF_TARGET_ESP32S3 ) || defined ( CONFIG_IDF_TARGET_ESP32C5 ) || defined ( CONFIG_IDF_TARGET_ESP32C6 ) || defined ( CONFIG_IDF_TARGET_ESP32C61 ) || defined ( CONFIG_IDF_TARGET_ESP32P4 ) || defined ( CONFIG_IDF_TARGET_ESP32H2 )
dev->to.time_out_value = 31;
dev->to.time_out_value = 21;
dev->to.time_out_en = 1;
#else
dev->timeout.tout = 0xFFFFF; // max 13ms
Expand Down Expand Up @@ -2296,6 +2326,7 @@ namespace lgfx
updateDev(dev);
dev->int_clr.val = intmask;
dev->ctr.trans_start = 1;
i2c_context[i2c_port].wait_ack_stage = 2;

uint32_t us = lgfx::micros();
taskYIELD();
Expand All @@ -2309,7 +2340,7 @@ namespace lgfx
do
{
taskYIELD();
} while ((len>>1) >= getRxFifoCount(dev) && !(dev->int_raw.val & intmask) && ((lgfx::micros() - us) <= us_limit + 1024));
} while ((len>>1) >= getRxFifoCount(dev) && !(dev->int_raw.val & intmask) && ((lgfx::micros() - us) <= us_limit + i2c_stall_limit_us));

if (0 == getRxFifoCount(dev))
{
Expand Down
2 changes: 1 addition & 1 deletion src/lgfx/v1/platforms/soft_i2c.inl
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Original file line number Diff line number Diff line change
Expand Up @@ -165,7 +165,7 @@ Contributors:
{
SOFT_I2C_YIELD();
if (gpio_in(ctx.pin_scl)) { return true; }
} while ((micros() - us) < 13000); // the same order as a peripheral timeout
} while ((micros() - us) < 25000); // the same stall allowance as the peripheral ports
return false;
}

Expand Down
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