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authorjaseg <git@jaseg.de>2023-09-25 23:57:36 +0200
committerjaseg <git@jaseg.de>2023-09-25 23:57:36 +0200
commit8cc05c79cea62609d02231492c054a0cca2b2289 (patch)
treee39d40456adefe9bb70bcd77ebdf97be1dcdc028 /center_fw/protocol.c
parent583ac10d1450610a4110849c26cc16f03154d26e (diff)
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Center firmware WIP
Diffstat (limited to 'center_fw/protocol.c')
-rw-r--r--center_fw/protocol.c149
1 files changed, 0 insertions, 149 deletions
diff --git a/center_fw/protocol.c b/center_fw/protocol.c
deleted file mode 100644
index dfa0d3e..0000000
--- a/center_fw/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;
-}
-