From b3ce046f7f9765561d8b6b6949801a0433460151 Mon Sep 17 00:00:00 2001 From: Jeremy Lakeman Date: Mon, 11 Nov 2013 13:38:31 +1030 Subject: [PATCH] Tweak radio link to reduce peak latency --- overlay_interface.c | 5 +- radio_link.c | 160 +++++++++++++++++++++++--------------------- radio_link.h | 2 +- 3 files changed, 85 insertions(+), 82 deletions(-) diff --git a/overlay_interface.c b/overlay_interface.c index 3c3bcea8..0ddbb7fa 100644 --- a/overlay_interface.c +++ b/overlay_interface.c @@ -716,10 +716,7 @@ static void interface_read_stream(struct overlay_interface *interface){ return; } - - int i; - for (i=0;iradio_link_state = emalloc_zero(sizeof(struct radio_link_state)); - interface->radio_link_state->network_coding = nc_new(16, LINK_PAYLOAD_MTU); + interface->radio_link_state->network_coding = nc_new(8, LINK_PAYLOAD_MTU); return 0; } @@ -348,7 +350,7 @@ int radio_link_tx(struct overlay_interface *interface) } int urgency = nc_tx_packet_urgency(link_state->network_coding); - time_ms_t delay = 600; + time_ms_t delay = 400; switch (urgency){ case URGENCY_ASAP: delay=5; @@ -402,7 +404,7 @@ static int parse_heartbeat(struct radio_link_state *state, const unsigned char * state->radio_rssi=(1.0*payload[10]-payload[13])/1.9; state->remote_rssi=(1.0*payload[11] - payload[14])/1.9; int free_space = payload[12]; - int free_bytes = (free_space * 1280) / 100 - 30; + int free_bytes = (free_space * SERIAL_BUFFER) / 100 - 30; state->remaining_space = free_bytes; if (free_bytes>0) state->next_tx_allowed = gettime_ms(); @@ -516,87 +518,91 @@ static int decode_length(struct radio_link_state *state, unsigned char *p) } // add one byte at a time from the serial link, and attempt to decode packets -int radio_link_decode(struct overlay_interface *interface, uint8_t c) +int radio_link_decode(struct overlay_interface *interface, uint8_t *buffer, ssize_t len) { IN(); struct radio_link_state *state=interface->radio_link_state; - - if (state->payload_start + state->payload_offset >= sizeof(state->payload)){ - // drop one byte if we run out of space - if (config.debug.radio_link) - DEBUGF("Dropped %02x, buffer full", state->payload[0]); - bcopy(state->payload+1, state->payload, sizeof(state->payload) -1); - state->payload_start--; - } - - unsigned char *p = &state->payload[state->payload_start]; - p[state->payload_offset++]=c; - - while(1){ - // look for packet length headers - p = &state->payload[state->payload_start]; - while(state->payload_length==0 && state->payload_offset>=6){ - if (p[0]==0xFE - && p[1]==9 - && p[3]==RADIO_SOURCE_SYSTEM - && p[4]==RADIO_SOURCE_COMPONENT - && p[5]==MAVLINK_MSG_ID_RADIO){ - //looks like a valid heartbeat response header, read the rest and process it - state->payload_length=17; - break; - } - - if (decode_length(state, &p[1])==0) - break; - - state->payload_start++; - state->payload_offset--; - p++; + int i; + for (i=0;ipayload_start + state->payload_offset >= sizeof(state->payload)){ + // drop one byte if we run out of space + if (config.debug.radio_link) + DEBUGF("Dropped %02x, buffer full", state->payload[0]); + bcopy(state->payload+1, state->payload, sizeof(state->payload) -1); + state->payload_start--; } - // wait for a whole packet - if (!state->payload_length || state->payload_offset < state->payload_length) - RETURN(0); + unsigned char *p = &state->payload[state->payload_start]; + p[state->payload_offset++]=c; - if (parse_heartbeat(state, p)){ - // cut the bytes of the heartbeat out of the buffer - state->payload_offset -= state->payload_length; - if (state->payload_offset){ - // shuffle bytes backwards - bcopy(&p[state->payload_length], p, state->payload_offset); + while(1){ + // look for packet length headers + p = &state->payload[state->payload_start]; + while(state->payload_length==0 && state->payload_offset>=6){ + if (p[0]==0xFE + && p[1]==9 + && p[3]==RADIO_SOURCE_SYSTEM + && p[4]==RADIO_SOURCE_COMPONENT + && p[5]==MAVLINK_MSG_ID_RADIO){ + //looks like a valid heartbeat response header, read the rest and process it + state->payload_length=17; + break; + } + + if (decode_length(state, &p[1])==0) + break; + + state->payload_start++; + state->payload_offset--; + p++; + } + + // wait for a whole packet + if (!state->payload_length || state->payload_offset < state->payload_length) + break; + + if (parse_heartbeat(state, p)){ + // cut the bytes of the heartbeat out of the buffer + state->payload_offset -= state->payload_length; + if (state->payload_offset){ + // shuffle bytes backwards + bcopy(&p[state->payload_length], p, state->payload_offset); + } + // restart parsing for a valid header from the beginning of out buffer + state->payload_offset+=state->payload_start; + state->payload_start=0; + state->payload_length=0; + continue; + } + + // is this a well formed packet? + int backtrack=0; + if (radio_link_parse(interface, state, state->payload_length, p, &backtrack)==1){ + // Since we know we've synced with the remote party, + // and there's nothing we can do about any earlier data + // throw away everything before the end of this packet + if (state->payload_start && config.debug.radio_link) + dump("Skipped", state->payload, state->payload_start); + + // If the packet is truncated by less than 16 bytes, RS protection should be enough to recover the packet, + // but we may need to examine the last few bytes to find the start of the next packet. + state->payload_offset -= state->payload_length - backtrack; + if (state->payload_offset){ + // shuffle all remaining bytes back to the start of the buffer + bcopy(&state->payload[state->payload_start + state->payload_length - backtrack], + state->payload, state->payload_offset); + } + state->payload_start=0; + }else{ + // ignore the first byte for now and start looking for another packet header + // we may find a heartbeat in the middle that we need to cut out first + state->payload_start++; + state->payload_offset--; } - // restart parsing for a valid header from the beginning of out buffer - state->payload_offset+=state->payload_start; - state->payload_start=0; state->payload_length=0; - continue; - } - - // is this a well formed packet? - int backtrack=0; - if (radio_link_parse(interface, state, state->payload_length, p, &backtrack)==1){ - // Since we know we've synced with the remote party, - // and there's nothing we can do about any earlier data - // throw away everything before the end of this packet - if (state->payload_start && config.debug.radio_link) - dump("Skipped", state->payload, state->payload_start); - - // If the packet is truncated by less than 16 bytes, RS protection should be enough to recover the packet, - // but we may need to examine the last few bytes to find the start of the next packet. - state->payload_offset -= state->payload_length - backtrack; - if (state->payload_offset){ - // shuffle all remaining bytes back to the start of the buffer - bcopy(&state->payload[state->payload_start + state->payload_length - backtrack], - state->payload, state->payload_offset); - } - state->payload_start=0; - }else{ - // ignore the first byte for now and start looking for another packet header - // we may find a heartbeat in the middle that we need to cut out first - state->payload_start++; - state->payload_offset--; - } - state->payload_length=0; - }; + }; + } RETURN(0); } diff --git a/radio_link.h b/radio_link.h index 1dd92ccf..4fef2f88 100644 --- a/radio_link.h +++ b/radio_link.h @@ -6,7 +6,7 @@ int radio_link_free(struct overlay_interface *interface); int radio_link_init(struct overlay_interface *interface); -int radio_link_decode(struct overlay_interface *interface, uint8_t c); +int radio_link_decode(struct overlay_interface *interface, uint8_t *buffer, ssize_t len); int radio_link_tx(struct overlay_interface *interface); void radio_link_state_html(struct strbuf *b, struct overlay_interface *interface); int radio_link_is_busy(struct overlay_interface *interface);