esb: Rename field in esb_radio_dynamic_pdu structure and update doc

Renamed field in esb_radio_dynamic_pdu structure
and updated documentation regarding selective_auto_ack

When dynamic ACK is enabled in the nRf24L01+ radio
the NOACK bit is inverted, compared to how it is
described in the documentation.
When dynamic ACK is enabled the NOACK bit is 1 if you want an ACK,
and 0 if you do not want an ACK.

Ref: NCSDK-36226

Signed-off-by: Marcin Jelinski <[email protected]>

Author: maje-emb

doc/nrf/protocols/esb/index.rst

@@ -125,7 +125,8 @@ However, repeated packets will always be ACKed by the PRX, even though they are
 
 A PTX can select that individual packets that are transmitted to the PRX do not require an ACK to be sent in return from the PRX.
 This decision is taken by the application when uploading a packet to the TX FIFO using the :c:member:`esb_payload.noack` field of the :c:struct:`esb_payload` parameter that is passed to the :c:func:`esb_write_payload` function.
-When the :c:member:`selective_auto_ack` field in the :c:struct:`esb_config` configuration structure is disabled, all packets will be acknowledged, ignoring the :c:member:`esb_payload.noack` field.
+When the :c:member:`esb_config.selective_auto_ack` field in the :c:struct:`esb_config` configuration structure is disabled, all packets will be acknowledged, ignoring the :c:member:`esb_payload.noack` field.
+The :c:member:`esb_config.selective_auto_ack` field must be configured with the same value on both the PTX and PRX sides to ensure consistent behavior.
 
 When the PRX receives a packet that does not require an ACK, it does not send an ACK packet to the PTX.
 In this case, when :c:member:`esb_payload.noack` = ``true``, packet retransmission does not occur.

subsys/esb/esb.c

@@ -204,8 +204,8 @@ struct esb_radio_dynamic_pdu {
 	uint8_t rfu0:2;
 #endif /* CONFIG_ESB_MAX_PAYLOAD_LENGTH > 63 */
 
-	/* Disable acknowledge. */
-	uint8_t no_ack:1;
+	/* Acknowledge. */
+	uint8_t ack:1;
 
 	/* Packet ID of the last received packet. Used to detect retransmits. */
 	uint8_t pid:2;
@@ -1127,7 +1127,7 @@ static bool rx_fifo_push_rfbuf(uint8_t pipe, uint8_t pid)
 	rx_fifo.payload[rx_fifo.back]->pipe = pipe;
 	rx_fifo.payload[rx_fifo.back]->rssi = nrf_radio_rssi_sample_get(NRF_RADIO);
 	rx_fifo.payload[rx_fifo.back]->pid = pid;
-	rx_fifo.payload[rx_fifo.back]->noack = !rx_pdu->type.dpl_pdu.no_ack;
+	rx_fifo.payload[rx_fifo.back]->noack = !rx_pdu->type.dpl_pdu.ack;
 
 	if (++rx_fifo.back >= CONFIG_ESB_RX_FIFO_SIZE) {
 		rx_fifo.back = 0;
@@ -1229,10 +1229,10 @@ static void start_tx_transaction(void)
 	case ESB_PROTOCOL_ESB_DPL:
 		memset(&pdu->type.dpl_pdu, 0, sizeof(pdu->type.dpl_pdu));
 		ack = !current_payload->noack || !esb_cfg.selective_auto_ack;
-
 		pdu->type.dpl_pdu.length = current_payload->length;
 		pdu->type.dpl_pdu.pid = current_payload->pid;
-		pdu->type.dpl_pdu.no_ack = current_payload->noack ? 0x00 : 0x01;
+		/* nRF24L01 chip inverts ACK bit */
+		pdu->type.dpl_pdu.ack = !current_payload->noack;
 
 		memcpy(pdu->data, current_payload->data, current_payload->length);
 
@@ -1657,7 +1657,7 @@ static void prepare_ack_pdu_dpl(bool retransmit_payload, struct pipe_info *pipe_
 	}
 
 	tx_pdu->type.dpl_pdu.pid = rx_pdu->type.dpl_pdu.pid;
-	tx_pdu->type.dpl_pdu.no_ack = rx_pdu->type.dpl_pdu.no_ack;
+	tx_pdu->type.dpl_pdu.ack = rx_pdu->type.dpl_pdu.ack;
 }
 
 static void on_radio_disabled_rx(void)
@@ -1690,7 +1690,7 @@ static void on_radio_disabled_rx(void)
 	pipe_info->crc = nrf_radio_rxcrc_get(NRF_RADIO);
 
 	/* Check if an ack should be sent */
-	if ((esb_cfg.selective_auto_ack == false) || rx_pdu->type.dpl_pdu.no_ack) {
+	if ((esb_cfg.selective_auto_ack == false) || rx_pdu->type.dpl_pdu.ack) {
 		esb_fem_for_tx_ack();
 
 		switch (esb_cfg.protocol) {