cpu/nrf52/radio/nrf802154: fix radio after soft ACK

cpu/native/socket_zep/socket_zep.c

@@ -511,14 +511,22 @@
     zepdev->state = ZEPDEV_STATE_TX;
 
     /* 8 bit are mapped to 2 symbols */
     unsigned time_tx = 2 * (zepdev->snd_len - sizeof(zep_v2_data_hdr_t)) * IEEE802154_SYMBOL_TIME_US;
     DEBUG("socket_zep::request_transmit(%u bytes, %u µs)\n", zepdev->snd_len, time_tx);
 
     dev->cb(dev, IEEE802154_RADIO_INDICATION_TX_START);
 
-    /* delay transmission to simulate airtime */
-    zepdev->ack_timer.callback = _send_frame;
-    ztimer_set(ZTIMER_USEC, &zepdev->ack_timer, time_tx);
+    /* native overhead prevents short timers from triggering in time,
+       send directly if delay is less than 200 µs */
+    if (time_tx <= 200) {
+        _send_frame(zepdev->ack_timer.arg);
+    }
+    else {
+        time_tx -= 200;
+        /* delay transmission to simulate airtime */
+        zepdev->ack_timer.callback = _send_frame;
+        ztimer_set(ZTIMER_USEC, &zepdev->ack_timer, time_tx);
+    }
 
     return 0;
 }

cpu/nrf52/radio/nrf802154/nrf802154_radio.c

@@ -60,7 +60,6 @@
                              RADIO_SHORTS_CCABUSY_DISABLE_Msk | \
                              RADIO_SHORTS_TXREADY_START_Msk)
 
-#define MAC_TIMER_CHAN_ACK  (0U)    /**< MAC timer channel for transmitting an ACK frame */
 #define MAC_TIMER_CHAN_IFS  (1U)    /**< MAC timer channel for handling IFS logic */
 
 static uint8_t rxbuf[IEEE802154_FRAME_LEN_MAX + 3]; /* len PHR + PSDU + LQI */
@@ -69,7 +68,6 @@ static uint8_t txbuf[IEEE802154_FRAME_LEN_MAX + 3]; /* len PHR + PSDU + LQI */
 typedef enum {
     STATE_IDLE,
     STATE_TX,
-    STATE_ACK,
     STATE_RX,
     STATE_CCA_CLEAR,
     STATE_CCA_BUSY,
@@ -415,6 +413,15 @@ static void _set_ifs_timer(bool lifs)
     timer_start(NRF802154_TIMER);
 }
 
+static void _timer_cb(void *arg, int chan)
+{
+    (void)arg;
+    if (chan == MAC_TIMER_CHAN_IFS) {
+        cfg.ifs = false;
+    }
+    timer_stop(NRF802154_TIMER);
+}
+
 /**
  * @brief   Set radio into DISABLED state
  */
@@ -424,6 +431,12 @@ int nrf802154_init(void)
     /* reset buffer */
     rxbuf[0] = 0;
     txbuf[0] = 0;
+
+    int result = timer_init(NRF802154_TIMER, TIMER_FREQ, _timer_cb, NULL);
+    assert(result >= 0);
+    (void)result;
+    timer_stop(NRF802154_TIMER);
+
     /* power off peripheral (but do not release the HFXO as we never requested
      * it so far) */
     NRF_RADIO->POWER = 0;
@@ -478,7 +491,6 @@ void isr_radio(void)
             break;
         case STATE_RX:
             if (NRF_RADIO->CRCSTATUS) {
-                bool l2filter_passed = _l2filter(rxbuf+1);
                 bool is_ack = rxbuf[1] & IEEE802154_FCF_TYPE_ACK;
 
                 /* If radio is in promiscuous mode, indicate packet and
@@ -488,21 +500,19 @@ void isr_radio(void)
                     _state = STATE_IDLE;
                     dev->cb(dev, IEEE802154_RADIO_INDICATION_RX_DONE);
                 }
-                /* If the L2 filter passes, device if the frame is indicated
-                 * directly or if the driver should send an ACK frame before
-                 * the indication */
-                else if (l2filter_passed) {
-                    DEBUG("[nrf802154] RX frame doesn't require ACK frame.\n");
-                    _state = STATE_IDLE;
-                    dev->cb(dev, IEEE802154_RADIO_INDICATION_RX_DONE);
-                }
                 /* In case the packet is an ACK and the ACK filter is disabled,
                  * indicate the frame reception */
                 else if (is_ack && !cfg.ack_filter) {
                     DEBUG("[nrf802154] Received ACK.\n");
                     _state = STATE_IDLE;
                     dev->cb(dev, IEEE802154_RADIO_INDICATION_RX_DONE);
                 }
+                /* If the L2 filter passes the frame is indicated directly */
+                else if (_l2filter(rxbuf+1)) {
+                    DEBUG("[nrf802154] RX data frame.\n");
+                    _state = STATE_IDLE;
+                    dev->cb(dev, IEEE802154_RADIO_INDICATION_RX_DONE);
+                }
                 /* If all failed, simply drop the frame and continue listening
                  * to incoming frames */
                 else {
@@ -515,16 +525,6 @@ void isr_radio(void)
                 dev->cb(dev, IEEE802154_RADIO_INDICATION_CRC_ERROR);
             }
             break;
-        case STATE_ACK:
-            _state = STATE_IDLE;
-
-            /* We disable the radio to avoid unwanted emissions (see ERRATA
-             * ID 204, "Switching between TX and RX causes unwanted emissions")
-             */
-            _disable();
-            DEBUG("[nrf52840] TX ACK done.");
-            _set_ifs_timer(false);
-            break;
         default:
             assert(false);
         }

sys/net/link_layer/ieee802154/submac.c

@@ -29,6 +29,17 @@
 
 #define CSMA_SENDER_BACKOFF_PERIOD_UNIT_US  (320U)
 #define ACK_TIMEOUT_US                      (864U)
+/* 2.4 GHz, 250 kb/s, O-QPSK 62.5 ksymbols/s, 1 / 62 500 s = 16 µs */
+/* 12 symbols -> 12 * 16us = 192us */
+#define SIFS_PERIOD_US                      (192U)
+
+/* internal type for IEEE 802.15.4 frame control field */
+enum ieee802154_fcf {
+    _FCF_BEACON     = IEEE802154_FCF_TYPE_BEACON,
+    _FCF_DATA       = IEEE802154_FCF_TYPE_DATA,
+    _FCF_ACK        = IEEE802154_FCF_TYPE_ACK,
+    _FCF_MACCMD     = IEEE802154_FCF_TYPE_MACCMD
+};
 
 static char *str_states[IEEE802154_FSM_STATE_NUMOF] = {
     "INVALID",
@@ -131,7 +142,8 @@
 }
 
 static ieee802154_fsm_state_t _fsm_state_prepare(ieee802154_submac_t *submac,
-                                                 ieee802154_fsm_ev_t ev);
+                                                 ieee802154_fsm_ev_t ev,
+                                                 enum ieee802154_fcf ftype);
 
 static ieee802154_fsm_state_t _fsm_state_tx(ieee802154_submac_t *submac,
                                             ieee802154_fsm_ev_t ev);
@@ -149,7 +161,7 @@
         return res;
     }
     /* skip async Tx request */
-    _fsm_state_prepare(submac, IEEE802154_FSM_EV_BH);
+    _fsm_state_prepare(submac, IEEE802154_FSM_EV_BH, IEEE802154_FCF_TYPE_ACK);
     /* wait for Tx done */
     while (_fsm_state_tx(submac, IEEE802154_FSM_EV_TX_DONE) == IEEE802154_FSM_STATE_INVALID) {
         DEBUG("IEEE802154 submac: wait until ACK sent\n");
@@ -254,13 +266,15 @@
 }
 
 static ieee802154_fsm_state_t _fsm_state_prepare(ieee802154_submac_t *submac,
-                                                 ieee802154_fsm_ev_t ev)
+                                                 ieee802154_fsm_ev_t ev,
+                                                 enum ieee802154_fcf ftype)
 {
     ieee802154_dev_t *dev = &submac->dev;
 
     switch (ev) {
     case IEEE802154_FSM_EV_BH:
-        if (!_does_handle_csma(dev)) {
+        if (ftype == IEEE802154_FCF_TYPE_DATA
+            && !_does_handle_csma(dev)) {
             /* delay for an adequate random backoff period */
             uint32_t bp = (random_uint32() & submac->backoff_mask) *
                           submac->csma_backoff_us;
@@ -272,6 +286,10 @@
                 submac->backoff_mask = (submac->backoff_mask << 1) | 1;
             }
         }
+        else if (ftype == IEEE802154_FCF_TYPE_ACK) {
+            /* no backoff for ACK frames but wait for SIFSPeriod */
+            ztimer_sleep(ZTIMER_USEC, SIFS_PERIOD_US);
+        }
 
         while (ieee802154_radio_request_transmit(dev) == -EBUSY) {}
         return IEEE802154_FSM_STATE_TX;
@@ -414,23 +432,23 @@
 
     switch (submac->fsm_state) {
     case IEEE802154_FSM_STATE_RX:
         DEBUG("IEEE802154 submac: ieee802154_submac_process_ev(): IEEE802154_FSM_STATE_RX + %s\n", str_ev[ev]);
         new_state = _fsm_state_rx(submac, ev);
         break;
     case IEEE802154_FSM_STATE_IDLE:
         DEBUG("IEEE802154 submac: ieee802154_submac_process_ev(): IEEE802154_FSM_STATE_IDLE + %s\n", str_ev[ev]);
         new_state = _fsm_state_idle(submac, ev);
         break;
     case IEEE802154_FSM_STATE_PREPARE:
         DEBUG("IEEE802154 submac: ieee802154_submac_process_ev(): IEEE802154_FSM_STATE_PREPARE + %s\n", str_ev[ev]);
-        new_state = _fsm_state_prepare(submac, ev);
+        new_state = _fsm_state_prepare(submac, ev, IEEE802154_FCF_TYPE_DATA);
         break;
     case IEEE802154_FSM_STATE_TX:
         DEBUG("IEEE802154 submac: ieee802154_submac_process_ev(): IEEE802154_FSM_STATE_TX + %s\n", str_ev[ev]);
         new_state = _fsm_state_tx(submac, ev);
         break;
     case IEEE802154_FSM_STATE_WAIT_FOR_ACK:
         DEBUG("IEEE802154 submac: ieee802154_submac_process_ev(): IEEE802154_FSM_STATE_WAIT_FOR_ACK + %s\n", str_ev[ev]);
         new_state = _fsm_state_wait_for_ack(submac, ev);
         break;
     default:
@@ -451,7 +469,7 @@
     ieee802154_fsm_state_t current_state = submac->fsm_state;
 
     if (current_state != IEEE802154_FSM_STATE_RX && current_state != IEEE802154_FSM_STATE_IDLE) {
         DEBUG("IEEE802154 submac: ieee802154_send(): Sending aborted, current state is %s\n", str_states[current_state]);
         return -EBUSY;
     }
 
@@ -472,12 +490,12 @@
 
     if (!is_ack && ieee802154_submac_process_ev(submac, IEEE802154_FSM_EV_REQUEST_TX)
         != IEEE802154_FSM_STATE_PREPARE) {
         DEBUG("IEEE802154 submac: ieee802154_send(): Tx frame failed %s\n", str_states[current_state]);
         return -EBUSY;
     }
     if (is_ack && ieee802154_submac_process_ev(submac, IEEE802154_FSM_EV_REQUEST_TX)
              != IEEE802154_FSM_STATE_IDLE) {
         DEBUG("IEEE802154 submac: ieee802154_send(): Tx ACK failed %s\n", str_states[current_state]);
         return -EBUSY;
     }
     return 0;