diff options
Diffstat (limited to 'center_fw/src/protocol.c')
| -rw-r--r-- | center_fw/src/protocol.c | 149 |
1 files changed, 0 insertions, 149 deletions
diff --git a/center_fw/src/protocol.c b/center_fw/src/protocol.c deleted file mode 100644 index dfa0d3e..0000000 --- a/center_fw/src/protocol.c +++ /dev/null @@ -1,149 +0,0 @@ -/* Control protocol receiver sitting between 8b10b.c and logical protocol handlers */ - -#include <unistd.h> -#include "protocol.h" -#include "8b10b.h" - -volatile uint32_t decoding_error_cnt = 0, protocol_error_cnt = 0; -volatile bool backchannel_frame = 0; - -/* Reset the given protocol state and register the command definition given with it. */ -void reset_receiver(struct proto_rx_st *st, const struct command_if_def *cmd_if) { - st->rxpos = -1; - st->address = 5; /* FIXME debug code */ - st->cmd_if = cmd_if; -} - -/* Receive an 8b10b symbol using the given protocol state. Handle any packets matching the enclosed command definition. - * - * This method is called from adc.c during the last bit period of the symbol, just before the actual end of the symbol - * and start of the next symbol. - */ -void receive_symbol(struct proto_rx_st *st, int symbol) { - - if (symbol == -K28_2) { /* Backchannel marker */ - /* This symbol is inserted into the symbol stream at regular intervals. It is not passed to the higher protocol - * layers but synchronizes the backchannel logic through all nodes. The backchannel works by a node putting a - * specified additional load of about 100mA (FIXME) on the line (1) or not (0) with all other nodes being - * silent. The master can detect this additional current. The backchannel is synchronized to the 8b10b frame - * being sent from the master, and the data is also 8b10b encoded. This means the backchannel is independent - * from the forward-channel. - * - * This means while the forward-channel (the line voltage) might go like the upper trace, the back-channel (the - * line current drawn by the node) might simultaneously look like the lower trace: - * - * Zoomed in on two master frames: - * - * |<--- D31.1 --->| |<--- D03.6 --->| - * Master -> Node 1 0 1 0 1 1 1 0 0 1 1 1 0 0 0 1 0 1 1 0 - * Voltage (V) .../^^\__/^^\__/^^^^^^^^\_____/^^^^^^^^\________/^^\__/^^^^^\___... - * - * Current (I) ...\_____________________________/^^^^^V^^^^^^^^V^^V^^V^^^^^V^^\... - * Node -> Master 0 1 - * - * - * Zoomed out on two node frames, or twenty master frames: - * - * Master -> Node | | | | | | | | | | | | | | | | | | |<- symbols, one after another - * Voltage (V) ...XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX... - * - * Current (I) ...___/^^^^^\__/^^\_____/^^\__/^^^^^\_____/^^\__/^^^^^\__/^^\___... - * Node -> Master 0 1 1 0 1 0 0 1 0 1 1 0 0 1 0 1 1 0 1 0 - * |<--- D22.2 --->| |<--- D09.5 --->| - * - * Note that during backchannel transmissions only one node transmits at a time, and all nodes including the - * transmitter keep their LEDs blanked to allow the master to more easily demodulate the transmission. - * - * This means that: - * * backchannel transmissions should be sparse (one per several regular symbols) to not affect brightness - * too much - * * backchannel transmissions should be spaced-out evenly and frequent enough to not cause visible flicker - * - * A consequence of this is that the backchannel has a bandwidth of only a fraction of the forward-channel. The - * master can dynamically adjust the frequency of the forward-channel and spacing of the backchannel markers. - * For 5kHz and 10% backchannel data (every tenth symbol being a backchannel symbol) the bandwidth works out to: - * - * BW(forward-channel) = 5 [kHz] / 10 [8b10b] = 500 byte/s - * BW(backchannel) = 5 [kHz] / 10 [8b10b] / 10 [every 10th symbol] / 10 [8b10b again] = 5 byte/s - * - * Luckily, we only use the backchannel for monitoring anyway and at ~20byte per monitoring frame we can easily - * monitor a bus-load (heh!) of nodes once a minute, which is enough for our purposes. - */ - - /* Blank the LEDs for the next frame to keep the bus quiet during backchannel transmission. This happens on all - * nodes. */ - backchannel_frame = true; - return; /* We're done handling this symbol */ - } else { - /* On anything else than a backchannel marker, turn off backchannel blanking for the next frame */ - backchannel_frame = false; - } - - if (symbol == -K28_1) { /* Comma/frame delimiter */ - st->rxpos = 0; - /* Fall through and return and just ignore incomplete packets */ - - } else if (symbol == -DECODING_ERROR) { - if (decoding_error_cnt < UINT32_MAX) - decoding_error_cnt++; - goto reset; - - } else if (symbol < 0) { /* Unknown comma symbol */ - if (protocol_error_cnt < UINT32_MAX) - protocol_error_cnt++; - goto reset; - - } else if (st->rxpos == -1) { /* Receiver freshly reset and no comma seen yet */ - return; - - } else if (st->rxpos == 0) { /* First data symbol, and not an error or comma symbol */ - st->packet_type = symbol & ~PKT_TYPE_BULK_FLAG; - if (st->packet_type >= st->cmd_if->packet_type_max) - goto reset; /* Not a protocol error */ - - /* If this a bulk packet, calculate and store the offset of our portion of it. Otherwise just prime the state - * for receiving the indidual packet by setting the offset to the first packet byte after the address. */ - int payload_len = st->cmd_if->payload_len[st->packet_type]; - st->is_bulk = symbol & PKT_TYPE_BULK_FLAG; - st->offset = (st->is_bulk) ? (st->address*payload_len + 1) : 2; - st->rxpos++; - - if (payload_len == 0 && st->is_bulk) { - /* Length-0 packet type, handle now for bulk packets as we don't know when the master will send the next - * comma or other symbol. For individually addressed packets, wait for the address byte. */ - handle_command(st->packet_type, NULL); - goto reset; - } - - } else if (!st->is_bulk && st->rxpos == 1) { /* First byte (address byte) of individually adressed packet */ - if (symbol != st->address) /* A different node is adressed */ - goto reset; - - if (st->cmd_if->payload_len[st->packet_type] == 0) { - /* Length-0 packet type, handle now as we don't know when the master will send the next comma or other - * symbol. */ - handle_command(st->packet_type, NULL); - goto reset; - } - st->rxpos++; - - } else { /* Receiving packet body */ - if (st->rxpos - st->offset >= 0) { - /* Either we're receiving an individually adressed packet adressed to us, or we're in the middle of a bulk - * packet at our offset */ - st->argbuf[st->rxpos - st->offset] = symbol; - } - st->rxpos++; - - if (st->rxpos - st->offset == st->cmd_if->payload_len[st->packet_type]) { - /* We're at the end of either an individual packet or our portion of a bulk packet. Handle packet here. */ - handle_command(st->packet_type, (uint8_t *)st->argbuf); - goto reset; - } - } - - return; -reset: - st->rxpos = -1; -} - |