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Get the last time when the tx write buffer got emptied #17978

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Get the last time when the tx write buffer got emptied #17978

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AP_HAL: get the last time when the tx write buffer got emptied
amilcarlucas Jul 8, 2021
252d6cc
AP_HAL_ChibiOS: get the last time when the tx write buffer got emptied
amilcarlucas Jul 8, 2021
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2 changes: 2 additions & 0 deletions libraries/AP_HAL/UARTDriver.h
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Original file line number Diff line number Diff line change
Expand Up @@ -151,6 +151,8 @@ class AP_HAL::UARTDriver : public AP_HAL::BetterStream {
*/
virtual bool is_dma_enabled() const { return false; }

virtual uint32_t get_last_tx_empty_us() const { return 0; }

#if HAL_UART_STATS_ENABLED
// request information on uart I/O for this uart, for @SYS/uarts.txt
virtual void uart_info(ExpandingString &str) {}
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5 changes: 5 additions & 0 deletions libraries/AP_HAL_ChibiOS/UARTDriver.cpp
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Expand Up @@ -146,6 +146,11 @@ void UARTDriver::uart_thread()
if (_tx_initialised && ((mask & EVT_TRANSMIT_DATA_READY) || need_tick || (hd_tx_active && (mask & EVT_TRANSMIT_END)))) {
_tx_timer_tick();
}

// record the time when a half-duplex TX buffer got emptied
if (_tx_initialised && hd_tx_active && (mask & EVT_TRANSMIT_END) && _writebuf.is_empty()) {
_last_write_completed_us = now;
}
}
}
#pragma GCC diagnostic pop
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7 changes: 7 additions & 0 deletions libraries/AP_HAL_ChibiOS/UARTDriver.h
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Expand Up @@ -131,6 +131,13 @@ class ChibiOS::UARTDriver : public AP_HAL::UARTDriver {
*/
bool is_dma_enabled() const override { return rx_dma_enabled && tx_dma_enabled; }

// get the last time when the tx write buffer got emptied
#if CH_CFG_USE_EVENTS == TRUE
uint32_t get_last_tx_empty_us() const override { return ((tx_dma_enabled || half_duplex) && _writebuf.is_empty()) ? _last_write_completed_us : 0; }
#else
uint32_t get_last_tx_empty_us() const override { return (tx_dma_enabled && _writebuf.is_empty()) ? _last_write_completed_us : 0; }
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why this depends on DMA config ?

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Because the _last_write_completed_us only gets written to if tx_dma_enabled == true

#endif

private:
const SerialDef &sdef;
bool rx_dma_enabled;
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