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Streaming write: 3x faster, remove per-packet backpressure #35

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Merged
widgetii merged 1 commit into from
Apr 6, 2026
Merged

Streaming write: 3x faster, remove per-packet backpressure #35

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11 changes: 4 additions & 7 deletions agent/main.c
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Original file line number Diff line number Diff line change
Expand Up @@ -227,9 +227,9 @@ static void handle_write(const uint8_t *data, uint32_t len) {
uint32_t chunk = pkt_len - 2;
for (uint32_t i = 0; i < chunk && received < size; i++)
dest[received++] = pkt[2 + i];
/* Backpressure: COBS-framed ACK after each DATA packet.
* Host waits for this before sending next packet. */
proto_send_ack(ACK_OK);
/* No per-packet ACK — streaming mode. COBS CRC32 per packet
* catches any corruption. D-cache makes processing fast
* enough to keep up with 921600 baud. */
} else if (cmd == 0) {
uint8_t err[5];
err[0] = ACK_FLASH_ERROR;
Expand Down Expand Up @@ -333,8 +333,6 @@ static void handle_flash_write(const uint8_t *data, uint32_t len) {
uint32_t chunk = pkt_len - 2;
for (uint32_t i = 0; i < chunk && received < size; i++)
staging[received++] = pkt[2 + i];
/* Backpressure ACK */
proto_send_ack(ACK_OK);
} else if (cmd == 0) {
uint8_t err[5];
err[0] = ACK_FLASH_ERROR;
Expand Down Expand Up @@ -540,8 +538,7 @@ static void handle_selfupdate(const uint8_t *data, uint32_t len) {
uint32_t chunk = pkt_len - 2;
for (uint32_t i = 0; i < chunk && received < size; i++)
dest[received++] = pkt[2 + i];
/* Backpressure ACK — host must wait before sending next */
proto_send_ack(ACK_OK);
/* Streaming mode — no per-packet ACK */
} else if (cmd == 0) {
proto_send_ack(ACK_FLASH_ERROR);
return;
Expand Down
19 changes: 4 additions & 15 deletions src/defib/agent/client.py
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Original file line number Diff line number Diff line change
Expand Up @@ -323,9 +323,9 @@ async def _write_block(self, addr: int, data: bytes) -> bool:
if cmd != RSP_ACK or resp[0] != ACK_OK:
return False

# Send data packets with backpressure: agent sends a COBS-framed
# ACK after each DATA packet. Host waits for it before sending
# next. Guarantees zero data loss at any speed.
# Stream all DATA packets without per-packet ACK.
# With COBS bug fixed + D-cache, the agent processes fast
# enough to keep up at 921600 baud.
offset = 0
seq = 0
while offset < len(data):
Expand All @@ -335,11 +335,6 @@ async def _write_block(self, addr: int, data: bytes) -> bool:
offset += chunk
seq += 1

# Wait for per-packet ACK
cmd, resp = await recv_response(self._transport, timeout=10.0)
if cmd != RSP_ACK or resp[0] != ACK_OK:
return False

# Final CRC verification ACK — may take seconds for large transfers
crc_timeout = max(60.0, len(data) / 50000) # ~20µs/byte for CRC32
cmd, resp = await recv_response(self._transport, timeout=crc_timeout)
Expand Down Expand Up @@ -603,7 +598,7 @@ async def selfupdate(
if cmd != RSP_ACK or resp[0] != ACK_OK:
return False

# Send data with per-packet backpressure
# Stream all data packets
offset = 0
seq = 0
while offset < len(firmware):
Expand All @@ -613,12 +608,6 @@ async def selfupdate(
offset += chunk
seq += 1

# Wait for per-packet ACK
cmd, resp = await recv_response(self._transport, timeout=10.0)
if cmd != RSP_ACK or resp[0] != ACK_OK:
logger.error("Selfupdate packet %d failed: 0x%02x", seq, resp[0])
return False

# Wait for CRC verification ACK (agent verifies before jumping)
cmd, resp = await recv_response(self._transport, timeout=30.0)
if cmd != RSP_ACK or resp[0] != ACK_OK:
Expand Down
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