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nimble/phy/nrf5x: Add support for FEM turn on time
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This adds proper support for FEM turn on time. Max supported turn on
time is 90us due to some optimizations in code, but that should be
enough - we can change it later if needed.
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@andrzej-kaczmarek
andrzej-kaczmarek committed Sep 14, 2022
1 parent 9ea411f commit f396441
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Showing 3 changed files with 147 additions and 57 deletions.
196 changes: 140 additions & 56 deletions nimble/drivers/nrf5x/src/ble_phy.c
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Original file line number Diff line number Diff line change
Expand Up @@ -606,41 +606,65 @@ ble_phy_tifs_get(void)
*
*/
static int
ble_phy_set_start_time(uint32_t cputime, uint8_t rem_usecs, bool tx)
ble_phy_set_start_time(uint32_t cputime, uint8_t rem_us, bool tx)
{
uint32_t next_cc;
uint32_t cur_cc;
uint32_t cntr;
uint32_t delta;
int radio_rem_us;
#if PHY_USE_FEM
int fem_rem_us = 0;
#endif
int rem_us_corr;
int min_rem_us;

/*
* We need to adjust start time to include radio ramp-up and TX pipeline
* delay (the latter only if applicable, so only for TX).
*
* Radio ramp-up time is 40 usecs and TX delay is 3 or 5 usecs depending on
* phy, thus we'll offset RTC by 2 full ticks (61 usecs) and then compensate
* using TIMER0 with 1 usec precision.
/* Calculate rem_us for radio and FEM enable. The result may be a negative
* value, but we'll adjust later.
*/

cputime -= 2;
rem_usecs += 61;
if (tx) {
rem_usecs -= BLE_PHY_T_TXENFAST;
rem_usecs -= g_ble_phy_t_txdelay[g_ble_phy_data.phy_cur_phy_mode];
radio_rem_us = rem_us - BLE_PHY_T_TXENFAST -
g_ble_phy_t_txdelay[g_ble_phy_data.phy_cur_phy_mode];
#if PHY_USE_FEM_PA
fem_rem_us = rem_us - MYNEWT_VAL(BLE_LL_FEM_PA_TURN_ON_US);
#endif
} else {
rem_usecs -= BLE_PHY_T_RXENFAST;
radio_rem_us = rem_us - BLE_PHY_T_TXENFAST;
#if PHY_USE_FEM_LNA
fem_rem_us = rem_us - MYNEWT_VAL(BLE_LL_FEM_LNA_TURN_ON_US);
#endif
}

/*
* rem_usecs will be no more than 2 ticks, but if it is more than single
* tick then we should better count one more low-power tick rather than
* 30 high-power usecs. Also make sure we don't set TIMER0 CC to 0 as the
* compare won't occur.
#if PHY_USE_FEM
min_rem_us = min(radio_rem_us, fem_rem_us);
#else
min_rem_us = radio_rem_us;
#endif

/* We need to adjust rem_us values, so they are >=1 for TIMER0 compare
* event to be triggered.
*
* If FEM is not enabled, calculated rem_us is -45<=rem_us<=-15 since we
* only had to adjust earlier for ramp-up and txdelay, i.e. 40+5=45us in
* worst case, so we adjust by 1 or 2 tick(s) only.
*
* If FEM is enabled, turn on time may be a bit longer, so we also allow to
* adjust by 3 ticks so up to 90us which should be enough. If needed, we
* can extend this by another tick but having FEM with turn on time >90us
* means transition may become tricky.
*/

if (rem_usecs > 30) {
cputime++;
rem_usecs -= 30;
if ((PHY_USE_FEM) && (min_rem_us <= -61)) {
cputime -= 3;
rem_us_corr = 91;
} else if (min_rem_us <= -30) {
/* rem_us is -60..-30 */
cputime -= 2;
rem_us_corr = 61;
} else {
/* rem_us is -29..0 */
cputime -= 1;
rem_us_corr = 30;
}

/*
Expand Down Expand Up @@ -668,15 +692,34 @@ ble_phy_set_start_time(uint32_t cputime, uint8_t rem_usecs, bool tx)

/* Clear and set TIMER0 to fire off at proper time */
nrf_timer_task_trigger(NRF_TIMER0, NRF_TIMER_TASK_CLEAR);
nrf_timer_cc_set(NRF_TIMER0, 0, rem_usecs);
nrf_timer_cc_set(NRF_TIMER0, 0, radio_rem_us + rem_us_corr);
NRF_TIMER0->EVENTS_COMPARE[0] = 0;
#if PHY_USE_FEM
if (fem_rem_us) {
nrf_timer_cc_set(NRF_TIMER0, 2, fem_rem_us + rem_us_corr);
NRF_TIMER0->EVENTS_COMPARE[2] = 0;
}
#endif

/* Set RTC compare to start TIMER0 */
NRF_RTC0->EVENTS_COMPARE[0] = 0;
nrf_rtc_cc_set(NRF_RTC0, 0, next_cc);
nrf_rtc_event_enable(NRF_RTC0, RTC_EVTENSET_COMPARE0_Msk);

/* Enable PPI */
#if PHY_USE_FEM
if (fem_rem_us) {
if (tx) {
#if PHY_USE_FEM_PA
phy_fem_enable_pa();
#endif
} else {
#if PHY_USE_FEM_LNA
phy_fem_enable_lna();
#endif
}
}
#endif
phy_ppi_rtc0_compare0_to_timer0_start_enable();

/* Store the cputime at which we set the RTC */
Expand All @@ -690,16 +733,41 @@ ble_phy_set_start_now(void)
{
os_sr_t sr;
uint32_t now;
uint32_t radio_rem_us;
#if PHY_USE_FEM_LNA
uint32_t fem_rem_us;
#endif

OS_ENTER_CRITICAL(sr);

/*
* Set TIMER0 to fire immediately. We can't set CC to 0 as compare will not
* occur in such case.
/* We need to set TIMER0 compare registers to at least 1 as otherwise
* compare event won't be triggered. Event (FEM/radio) that have to be
* triggered first is set to 1, other event is set to 1+diff.
*
* Note that this is only used for rx, so only need to handle LNA.
*/

#if PHY_USE_FEM_LNA
if (MYNEWT_VAL(BLE_LL_FEM_LNA_TURN_ON_US) > BLE_PHY_T_RXENFAST) {
radio_rem_us = 1 + MYNEWT_VAL(BLE_LL_FEM_LNA_TURN_ON_US) -
BLE_PHY_T_RXENFAST;
fem_rem_us = 1;
} else {
radio_rem_us = 1;
fem_rem_us = 1 + BLE_PHY_T_RXENFAST -
MYNEWT_VAL(BLE_LL_FEM_LNA_TURN_ON_US);
}
#else
radio_rem_us = 1;
#endif

nrf_timer_task_trigger(NRF_TIMER0, NRF_TIMER_TASK_CLEAR);
nrf_timer_cc_set(NRF_TIMER0, 0, 1);
nrf_timer_cc_set(NRF_TIMER0, 0, radio_rem_us);
NRF_TIMER0->EVENTS_COMPARE[0] = 0;
#if PHY_USE_FEM_LNA
nrf_timer_cc_set(NRF_TIMER0, 2, fem_rem_us);
NRF_TIMER0->EVENTS_COMPARE[2] = 0;
#endif

/*
* Set RTC compare to start TIMER0. We need to set it to at least N+2 ticks
Expand Down Expand Up @@ -939,6 +1007,10 @@ ble_phy_tx_end_isr(void)
uint8_t transition;
uint32_t rx_time;
uint32_t tx_time;
#if PHY_USE_FEM_LNA
uint32_t fem_time;
#endif
uint32_t radio_time;

/* Store PHY on which we've just transmitted smth */
tx_phy_mode = g_ble_phy_data.phy_cur_phy_mode;
Expand Down Expand Up @@ -983,32 +1055,42 @@ ble_phy_tx_end_isr(void)
rx_time = NRF_TIMER0->CC[2] + ble_phy_tifs_get();
/* Adjust for delay between EVENT_END and actual TX end time */
rx_time += g_ble_phy_t_txenddelay[tx_phy_mode];
/* Adjust for radio ramp-up */
rx_time -= BLE_PHY_T_RXENFAST;
/* Start listening a bit earlier due to allowed active clock accuracy */
rx_time -= 2;

nrf_timer_cc_set(NRF_TIMER0, 0, rx_time);
NRF_TIMER0->EVENTS_COMPARE[0] = 0;
phy_ppi_timer0_compare0_to_radio_rxen_enable();

#if PHY_USE_FEM_LNA
fem_time = rx_time - MYNEWT_VAL(BLE_LL_FEM_LNA_TURN_ON_US);
nrf_timer_cc_set(NRF_TIMER0, 2, fem_time);
NRF_TIMER0->EVENTS_COMPARE[2] = 0;
phy_fem_enable_lna();
#endif

radio_time = rx_time - BLE_PHY_T_RXENFAST;
nrf_timer_cc_set(NRF_TIMER0, 0, radio_time);
NRF_TIMER0->EVENTS_COMPARE[0] = 0;
phy_ppi_timer0_compare0_to_radio_rxen_enable();

/* In case TIMER0 did already count past CC[0] and/or CC[2], radio
* and/or LNA may not be enabled. In any case we won't be stuck since
* wfr will cancel rx if needed.
*
* FIXME failing to enable LNA may result in unexpected RSSI drop in
* case we still rxd something, so perhaps we could check it here
*/
} else if (transition == BLE_PHY_TRANSITION_TX_TX) {
/* Schedule TX exactly T_IFS after TX end captured in CC[2] */
tx_time = NRF_TIMER0->CC[2] + ble_phy_tifs_get();
/* Adjust for delay between EVENT_END and actual TX end time */
tx_time += g_ble_phy_t_txenddelay[tx_phy_mode];
/* Adjust for radio ramp-up */
tx_time -= BLE_PHY_T_TXENFAST;
/* Adjust for delay between EVENT_READY and actual TX start time */
tx_time -= g_ble_phy_t_txdelay[g_ble_phy_data.phy_cur_phy_mode];

nrf_timer_cc_set(NRF_TIMER0, 0, tx_time);
NRF_TIMER0->EVENTS_COMPARE[0] = 0;
phy_ppi_timer0_compare0_to_radio_txen_enable();

/* TODO handle PA */

nrf_timer_task_trigger(NRF_TIMER0, NRF_TIMER_TASK_CAPTURE3);
if (NRF_TIMER0->CC[3] > NRF_TIMER0->CC[0]) {
phy_ppi_timer0_compare0_to_radio_txen_disable();
Expand Down Expand Up @@ -1060,7 +1142,12 @@ ble_phy_rx_end_isr(void)
uint8_t *dptr;
uint8_t crcok;
uint32_t tx_time;
#if PHY_USE_FEM_PA
uint32_t fem_time;
#endif
uint32_t radio_time;
struct ble_mbuf_hdr *ble_hdr;
bool is_late;

/* Disable automatic RXEN */
phy_ppi_timer0_compare0_to_radio_rxen_disable();
Expand Down Expand Up @@ -1128,33 +1215,38 @@ ble_phy_rx_end_isr(void)
tx_time = NRF_TIMER0->CC[2] + ble_phy_tifs_get();
/* Adjust for delay between actual RX end time and EVENT_END */
tx_time -= g_ble_phy_t_rxenddelay[ble_hdr->rxinfo.phy_mode];
/* Adjust for radio ramp-up */
tx_time -= BLE_PHY_T_TXENFAST;

#if PHY_USE_FEM_PA
fem_time = tx_time - MYNEWT_VAL(BLE_LL_FEM_PA_TURN_ON_US);
#endif

/* Adjust for delay between EVENT_READY and actual TX start time */
tx_time -= g_ble_phy_t_txdelay[g_ble_phy_data.phy_cur_phy_mode];

nrf_timer_cc_set(NRF_TIMER0, 0, tx_time);
radio_time = tx_time - BLE_PHY_T_TXENFAST;
nrf_timer_cc_set(NRF_TIMER0, 0, radio_time);
NRF_TIMER0->EVENTS_COMPARE[0] = 0;
phy_ppi_timer0_compare0_to_radio_txen_enable();

#if PHY_USE_FEM_PA
nrf_timer_cc_set(NRF_TIMER0, 2, fem_time);
NRF_TIMER0->EVENTS_COMPARE[2] = 0;
phy_fem_enable_pa();
#endif

/*
* XXX: Hack warning!
*
* It may happen (during flash erase) that CPU is stopped for a moment and
* TIMER0 already counted past CC[0]. In such case we will be stuck waiting
* for TX to start since EVENTS_COMPARE[0] will not happen any time soon.
* For now let's set a flag denoting that we are late in RX-TX transition so
* ble_phy_tx() will fail - this allows everything to cleanup nicely without
* the need for extra handling in many places.
/* Need to check if TIMER0 did not already count past CC[0] and/or CC[2], so
* we're not stuck waiting for events in case radio and/or PA was not
* started. If event was triggered we're fine regardless of timer value.
*
* Note: CC[3] is used only for wfr which we do not need here.
*/
nrf_timer_task_trigger(NRF_TIMER0, NRF_TIMER_TASK_CAPTURE3);
if (NRF_TIMER0->CC[3] > NRF_TIMER0->CC[0]) {
is_late = (NRF_TIMER0->CC[3] > radio_time) && !NRF_TIMER0->EVENTS_COMPARE[0];
#if PHY_USE_FEM_PA
is_late = is_late ||
((NRF_TIMER0->CC[3] > fem_time) && !NRF_TIMER0->EVENTS_COMPARE[2]);
#endif
if (is_late) {
phy_ppi_timer0_compare0_to_radio_txen_disable();
g_ble_phy_data.phy_transition_late = 1;
}
Expand Down Expand Up @@ -1644,10 +1736,6 @@ ble_phy_tx_set_start_time(uint32_t cputime, uint8_t rem_usecs)
/* Enable PPI to automatically start TXEN */
phy_ppi_timer0_compare0_to_radio_txen_enable();
rc = 0;

#if PHY_USE_FEM_PA
phy_fem_enable_pa();
#endif
}

return rc;
Expand Down Expand Up @@ -1694,10 +1782,6 @@ ble_phy_rx_set_start_time(uint32_t cputime, uint8_t rem_usecs)
/* Enable PPI to automatically start RXEN */
phy_ppi_timer0_compare0_to_radio_rxen_enable();

#if PHY_USE_FEM_LNA
phy_fem_enable_lna();
#endif

/* Start rx */
rc = ble_phy_rx();

Expand Down
2 changes: 1 addition & 1 deletion nimble/drivers/nrf5x/src/nrf52/phy.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -102,7 +102,7 @@ phy_fem_init(void)
#endif
#endif /* PHY_USE_FEM_SINGLE_GPIO */

NRF_PPI->CH[6].EEP = (uint32_t)&(NRF_RADIO->EVENTS_READY);
NRF_PPI->CH[6].EEP = (uint32_t)&(NRF_TIMER0->EVENTS_COMPARE[2]);
NRF_PPI->CH[7].EEP = (uint32_t)&(NRF_RADIO->EVENTS_DISABLED);

nrf_ppi_channels_disable(NRF_PPI, PPI_CHEN_CH6_Msk | PPI_CHEN_CH7_Msk);
Expand Down
6 changes: 6 additions & 0 deletions nimble/drivers/nrf5x/syscfg.yml
View file
Original file line number Diff line number Diff line change
Expand Up @@ -52,3 +52,9 @@ syscfg.defs:
in UICR register. If enabled public address will be read from
custom UICR instead of FICR register.
value: 0

syscfg.restrictions:
# code supports turn on times up to 90us due to some optimizations, but it
# should be enough for most (all?) cases
- "!BLE_LL_FEM_PA || BLE_LL_FEM_PA_TURN_ON_US <= 90"
- "!BLE_LL_FEM_LNA || BLE_LL_FEM_LNA_TURN_ON_US <= 90"

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