Changes between Version 5 and Version 6 of 802.11/wlan_exp/app_notes/tutorial_token_mac/CPU_LOW

Timestamp:

Jul 9, 2015, 4:44:57 PM (9 years ago)

Author:

chunter

Comment:

--

802.11/wlan_exp/app_notes/tutorial_token_mac/CPU_LOW

@@ -259 +259 @@
 === NoMAC ===
 
-Changes should be made to [browser:ReferenceDesigns/w3_802.11/c/wlan_mac_low_nomac/wlan_mac_nomac.c wlan_mac_nomac.c].
-
-NoMAC is intended to be a near "blank slate" to make building totally custom MACs more straightforward. It does not have any of the complexities of the DCF. Transmissions are directly connected to the PHY. There is no carrier sensing, no acknowledgments, no retransmissions, no random backoffs, etc. NoMAC is the perfect place for us to add the low-level behavior of TokenMAC.
+Changes should be made to [browser:ReferenceDesigns/w3_802.11/c/wlan_mac_low_nomac/wlan_mac_nomac.c wlan_mac_nomac.c] and [browser:ReferenceDesigns/w3_802.11/c/wlan_mac_low_nomac/include/wlan_mac_nomac.h wlan_mac_nomac.h].
+
+NoMAC is intended to be a near "blank slate" to make building totally custom MACs more straightforward. It does not have any of the complexities of the DCF. Transmissions are directly connected to the PHY. There is no carrier sensing, no acknowledgments, no retransmissions, no random backoffs, etc. NoMAC is the perfect place for us to add the low-level behavior of TokenMAC. We will construct TokenMAC in such a way that the same CPU_LOW project can be attached to either the AP or STA CPU_HIGH project to program a board. In other words, our modifications to NoMAC will have to work for either role of issuing tokens or accepting tokens.
 
 ---- 
+
+First, we need to modify [browser:ReferenceDesigns/w3_802.11/c/wlan_mac_low_nomac/include/wlan_mac_nomac.h wlan_mac_nomac.h] with a few new definitions.
+
+{{{
+#!c
+
+#define TX_PKT_BUF_TOKEN           7
+
+#define MAC_HW_LASTBYTE_TOKEN (sizeof(mac_frame_custom_token)+3)
+
+typedef struct{
+        u8 frame_control_1;
+        u8 frame_control_2;
+        u16 duration_id;
+        u8 address_ra[6];
+        u8 address_ta[6];
+        u32 res_duration_usec;
+} mac_frame_custom_token;
+}}}
+
+We will use {{{TX_PKT_BUF_TOKEN}}} as a hardcoded packet buffer index that is dedicated to transmitting our new token frames. {{{mac_frame_custom_token}}} is a struct that is our new custom token frame. It's format is inspired by 802.11 frames in order to allow nearby commercial Wi-Fi devices to decode and ignore these frames. We'll set the {{{frame_control_1}}} field to an invalid value to make ensure this.
+
+----
+
+Next, we will perform a little bit of bookkeeping and declare two new global variables we will need at the top of [browser:ReferenceDesigns/w3_802.11/c/wlan_mac_low_nomac/wlan_mac_nomac.c wlan_mac_nomac.c]:
+
+{{{
+#!c
+
+u8 in_reservation;
+u64 reservation_ts_end;
+}}}
+
+We will explain how we will use these new variables in the next sections. In {{{main()}}}, we also need to set some sane defaults:
+
+{{{
+#!c
+
+        in_reservation = 0;
+        wlan_mac_low_set_new_reservation_callback((void*)token_new_reservation);
+        wlan_mac_low_set_adjust_reservation_ts_callback((void*)adjust_reservation_ts_end);
+}}}
+
+We have not created the {{{token_new_reservation()}}} or {{{adjust_reservation_ts_end()}}} functions yet. We will add those in the coming sections.
+
+----
+The first substantive addition we will make to the NoMAC project is a function to deal with the IPC from CPU_HIGH that says we are now entering a new token reservation period for some given address and for some given duration of time. Add the following function to NoMAC:
+
+{{{
+#!c
+
+void token_new_reservation(ipc_token_new_reservation* new_reservation){
+
+        u8 mac_cfg_rate;
+        u16 mac_cfg_length;
+        int curr_tx_pow;
+        u32 mac_hw_status;
+        u32 rx_status;
+
+        wlan_ipc_msg       ipc_msg_to_high_start;
+        ipc_token_new_reservation ipc_payload_start;
+        wlan_ipc_msg       ipc_msg_to_high_end;
+        ipc_token_end_reservation ipc_payload_end;
+
+
+        ipc_msg_to_high_start.msg_id            = IPC_MBOX_MSG_ID(IPC_MBOX_TOKEN_NEW_RESERVATION);
+
+        if( (sizeof(u32)*(sizeof(ipc_token_new_reservation)/sizeof(u32))) ==  sizeof(ipc_token_new_reservation) ){
+                ipc_msg_to_high_start.num_payload_words = (sizeof(ipc_token_new_reservation)/sizeof(u32));
+        } else {
+                ipc_msg_to_high_start.num_payload_words = (sizeof(ipc_token_new_reservation)/sizeof(u32)) + 1;
+        }
+
+        ipc_msg_to_high_start.payload_ptr       = (u32*)(&ipc_payload_start);
+
+        ipc_msg_to_high_end.msg_id            = IPC_MBOX_MSG_ID(IPC_MBOX_TOKEN_END_RESERVATION);
+
+        if( (sizeof(u32)*(sizeof(ipc_token_end_reservation)/sizeof(u32))) ==  sizeof(ipc_token_end_reservation) ){
+                ipc_msg_to_high_end.num_payload_words = (sizeof(ipc_token_end_reservation)/sizeof(u32));
+        } else {
+                ipc_msg_to_high_end.num_payload_words = (sizeof(ipc_token_end_reservation)/sizeof(u32)) + 1;
+        }
+
+        ipc_msg_to_high_end.payload_ptr       = (u32*)(&ipc_payload_end);
+
+        mac_cfg_rate = WLAN_PHY_RATE_BPSK12;
+
+        if(wlan_addr_eq(new_reservation->addr, eeprom_addr)){
+                //This is my reservation
+                in_reservation = 1;
+                wlan_mac_low_enable_new_mpdu_tx();
+                reservation_ts_end = get_usec_timestamp() + ((u64)new_reservation->res_duration);
+
+                memcpy( ipc_payload_start.addr, new_reservation->addr, 6 );
+                ipc_payload_start.res_duration = new_reservation->res_duration;
+                ipc_mailbox_write_msg(&ipc_msg_to_high_start);
+
+        } else {
+                //This is someone else's reservation
+                mac_cfg_length = wlan_create_token_offer_frame((void*)(TX_PKT_BUF_TO_ADDR(TX_PKT_BUF_TOKEN) + PHY_TX_PKT_BUF_MPDU_OFFSET),
+                                                                                   new_reservation->addr,
+                                                                                   eeprom_addr,
+                                                                                   0,
+                                                                                   new_reservation->res_duration); //TODO: Calculate appropriate duration
+
+
+
+                wlan_phy_set_tx_signal(TX_PKT_BUF_TOKEN, mac_cfg_rate, mac_cfg_length); // Write SIGNAL for RTS
+
+                curr_tx_pow = wlan_mac_low_dbm_to_gain_target(15);
+                wlan_mac_tx_ctrl_A_gains(curr_tx_pow, curr_tx_pow, curr_tx_pow, curr_tx_pow);
+
+                //wlan_mac_tx_ctrl_A_params(pktBuf, antMask, preTx_backoff_slots, preWait_postRxTimer1, preWait_postTxTimer1, postWait_postTxTimer2)
+                //postTxTimer2 is a timeout. We'll use that to wait for a token response
+                wlan_mac_tx_ctrl_A_params(TX_PKT_BUF_TOKEN, 0x1, 0, 0, 0, 1);
+
+                //Start the Tx state machine
+                wlan_mac_tx_ctrl_A_start(1);
+                wlan_mac_tx_ctrl_A_start(0);
+
+                //Wait for the MPDU Tx to finish
+                do { //while(tx_status & WLAN_MAC_STATUS_MASK_TX_A_PENDING)
+
+                        //Poll the DCF core status register
+                        mac_hw_status = wlan_mac_get_status();
+
+                        if( mac_hw_status & WLAN_MAC_STATUS_MASK_TX_A_DONE ) {
+                                //Transmission is complete
+
+                                memcpy( ipc_payload_start.addr, new_reservation->addr, 6 );
+                                ipc_payload_start.res_duration = new_reservation->res_duration;
+                                ipc_mailbox_write_msg(&ipc_msg_to_high_start);
+
+                                //Switch on the result of the transmission attempt
+                                switch( mac_hw_status & WLAN_MAC_STATUS_MASK_TX_A_RESULT ) {
+                                        case WLAN_MAC_STATUS_TX_A_RESULT_RX_STARTED:
+                                                //Transmission ended, followed by a new reception (hopefully a token response)
+
+                                                //Handle the new reception
+                                                rx_status = wlan_mac_low_poll_frame_rx();
+
+                                                //Check if the reception is an ACK addressed to this node, received with a valid checksum
+                                                if( (rx_status & POLL_MAC_STATUS_TOKEN_OFFER_ACCEPTED)) {
+
+                                                        //We are now in a new reservation state for this user
+                                                        in_reservation = 1;
+                                                        reservation_ts_end = get_usec_timestamp() + ((u64)new_reservation->res_duration);
+                                                } else {
+                                                        //Received a packet immediately after transmitting, but it wasn't the offer response we wanted
+                                                        //This is equivalent to a timeout. Let CPU_HIGH know that this reservation period is over
+                                                        in_reservation = 0;
+                                                        ipc_payload_end.reason = TOKEN_TIMEOUT;
+                                                        //ipc_payload.low_tx_details; //TODO
+                                                        ipc_mailbox_write_msg(&ipc_msg_to_high_end);
+                                                }
+                                        break;
+                                        case WLAN_MAC_STATUS_TX_A_RESULT_TIMEOUT:
+                                                in_reservation = 0;
+                                                ipc_payload_end.reason = TOKEN_TIMEOUT;
+                                                //ipc_payload.low_tx_details; //TODO
+                                                ipc_mailbox_write_msg(&ipc_msg_to_high_end);
+                                        break;
+                                }
+                        } else { //else for if(mac_hw_status & WLAN_MAC_STATUS_MASK_TX_A_DONE)
+                                //Poll the MAC Rx state to check if a packet was received while our Tx was deferring
+
+                                if( mac_hw_status & (WLAN_MAC_STATUS_MASK_RX_PHY_ACTIVE | WLAN_MAC_STATUS_MASK_RX_PHY_BLOCKED_FCS_GOOD | WLAN_MAC_STATUS_MASK_RX_PHY_BLOCKED) ) {
+                                        rx_status = wlan_mac_low_poll_frame_rx();
+                                }
+                        }//END if(Tx A state machine done)
+                } while( mac_hw_status & WLAN_MAC_STATUS_MASK_TX_A_PENDING );
+        }
+}
+}}}
+
+----