c6_frame.c File Reference

Hand-decoded esp-hosted payload header for the ESP32-C6 SPI probe. More...

#include <stdint.h>
#include "c6_probe.h"
#include "c6_proto.h"

Include dependency graph for c6_frame.c:

Go to the source code of this file.

Functions
static uint16_t	internal_le16 (const uint8_t *buf, uint8_t off_lo)
	Read a little-endian 16-bit field out of a byte buffer.
uint16_t	c6_probe_checksum (const uint8_t *buf, uint16_t count)
	Recompute the esp-hosted checksum over a received frame.
void	c6_probe_decode_header (const uint8_t *buf, c6_hdr_t *out)
	Unpack the twelve-byte esp-hosted payload header.
c6_frame_kind_t	c6_probe_classify (const c6_hdr_t *h)
	Implementation of c6_probe_classify() – filler check first.
void	c6_probe_print_header (const c6_hdr_t *h)
	Print the decoded header fields on one console line.
void	c6_probe_dump_payload (const uint8_t *buf, uint16_t len)
	Hex-dump the leading payload bytes of a received frame.

Detailed Description

Hand-decoded esp-hosted payload header for the ESP32-C6 SPI probe.

Tag

[Ring 6 / APP] {World: S}

Unpacks and judges struct esp_payload_header (esp-hosted-mcu common/esp_hosted_header.h, pinned commit 949bb30) straight out of the receive buffer, without vendoring any upstream source. Field offsets, endianness and the acceptance rules all live in c6_proto.h next to the upstream file they were read from.

Copyright

Copyright (c) 2026 Brighton Sikarskie SPDX-License-Identifier: MIT

Since

0.1.0

Definition in file c6_frame.c.

Function Documentation

c6_probe_checksum()

uint16_t c6_probe_checksum	(	const uint8_t *	buf,
		uint16_t	count )

Recompute the esp-hosted checksum over a received frame.

compute_checksum() in esp-hosted-mcu common/transport/esp_hosted_transport.h is a plain 16-bit sum of every byte from the start of the header through the end of the payload. Both peers zero the checksum field before summing (process_spi_rx_buf in host/drivers/transport/spi/spi_drv.c), so the two checksum bytes are skipped here instead of being cleared, which leaves the receive buffer intact for the hex dump.

Parameters

[in]	buf	Receive buffer.
[in]	count	Bytes to sum: header offset plus payload length.

Returns

The 16-bit sum, or zero when buf is NULL.

Return values

0	buf was NULL, count was zero, or the sum is zero.

Precondition

buf holds at least count bytes.

count is no larger than k_c6_proto_buf_size.

Postcondition

The buffer is unmodified.

Overflow wraps at 16 bits, exactly as upstream does.

Note

Requires buf to be stable for the duration of the call.

Example:

const uint16_t sum = c6_probe_checksum(rx, (uint16_t)(h.offset + h.len));

See also

c6_probe_decode_header

Since

0.1.0

Definition at line 55 of file c6_frame.c.

References k_c6_hdr_off_csum_hi, k_c6_hdr_off_csum_lo, and k_c6_proto_buf_size.

Referenced by c6_probe_decode_header().

c6_probe_classify()

c6_frame_kind_t c6_probe_classify

(

const c6_hdr_t *

h

)

Implementation of c6_probe_classify() – filler check first.

Judge a decoded header against the upstream receive rules.

Definition at line 95 of file c6_frame.c.

References c6_hdr_t::checksum, c6_hdr_t::computed, c6_hdr_t::if_num, c6_hdr_t::if_type, k_c6_dummy_if_num, k_c6_frame_bad_csum, k_c6_frame_data, k_c6_frame_garbage, k_c6_frame_idle, k_c6_if_max, k_c6_proto_hdr_size, k_c6_proto_payload_max, c6_hdr_t::len, and c6_hdr_t::offset.

Referenced by internal_report_frame().

c6_probe_decode_header()

void c6_probe_decode_header	(	const uint8_t *	buf,
		c6_hdr_t *	out )

Unpack the twelve-byte esp-hosted payload header.

Parameters

[in]	buf	Receive buffer holding a completed transaction.
[out]	out	Decoded header; ignored when NULL.

Precondition

buf holds at least k_c6_proto_hdr_size bytes.

out is non-NULL for anything to be stored.

Postcondition

Every out field is populated from the wire bytes.

out->computed holds the locally recomputed checksum.

Note

Performs no validation; c6_probe_classify judges the result.

Example:

c6_hdr_t h = {};
c6_probe_decode_header(rx, &h);

See also

c6_probe_classify

Since

0.1.0

Definition at line 72 of file c6_frame.c.

References c6_probe_checksum(), c6_hdr_t::checksum, c6_hdr_t::computed, c6_hdr_t::flags, c6_hdr_t::if_num, c6_hdr_t::if_type, internal_le16(), k_c6_hdr_off_csum_lo, k_c6_hdr_off_flags, k_c6_hdr_off_iface, k_c6_hdr_off_len_lo, k_c6_hdr_off_off_lo, k_c6_hdr_off_pkttype, k_c6_hdr_off_seq_lo, k_c6_hdr_off_throttle, k_c6_mask_nibble, k_c6_mask_throttle, k_c6_proto_hdr_size, k_c6_proto_payload_max, k_c6_shift_nibble, c6_hdr_t::len, c6_hdr_t::offset, c6_hdr_t::pkt_type, c6_hdr_t::seq_num, and c6_hdr_t::throttle.

Referenced by internal_report_frame().

c6_probe_dump_payload()

void c6_probe_dump_payload	(	const uint8_t *	buf,
		uint16_t	len )

Hex-dump the leading payload bytes of a received frame.

Parameters

[in]	buf	Receive buffer.
[in]	len	Payload length claimed by the header.

Precondition

The board UART console has been initialised.

buf holds a completed transaction.

Postcondition

At most k_c6_probe_dump_bytes payload bytes were printed.

buf is unmodified.

Note

Not thread-safe.

Example:

c6_probe_dump_payload(rx, h.len);

See also

c6_probe_print_header

Since

0.1.0

Definition at line 142 of file c6_frame.c.

References c6_probe_put_hex(), c6_probe_puts(), k_c6_fmt_hex_byte, k_c6_probe_dump_bytes, and k_c6_proto_hdr_size.

Referenced by internal_report_frame().

c6_probe_print_header()

void c6_probe_print_header

(

const c6_hdr_t *

h

)

Print the decoded header fields on one console line.

Parameters

[in]

h

Decoded header; ignored when NULL.

Precondition

The board UART console has been initialised.

h is non-NULL for anything to be printed.

Postcondition

Exactly one console line was emitted when h is non-NULL.

h is unmodified.

Note

Not thread-safe.

Example:

c6_probe_print_header(&h);

See also

c6_probe_dump_payload

Since

0.1.0

Definition at line 116 of file c6_frame.c.

References c6_probe_put_hex(), c6_probe_put_u32(), c6_probe_puts(), c6_hdr_t::checksum, c6_hdr_t::computed, c6_hdr_t::flags, c6_hdr_t::if_num, c6_hdr_t::if_type, k_c6_fmt_hex_byte, k_c6_fmt_hex_word, c6_hdr_t::len, c6_hdr_t::offset, c6_hdr_t::pkt_type, and c6_hdr_t::seq_num.

Referenced by internal_report_frame().

internal_le16()

uint16_t internal_le16 ( const uint8_t * buf, uint8_t off_lo )

static

Read a little-endian 16-bit field out of a byte buffer.

Matches le16toh as used throughout esp-hosted-mcu, and is byte-order-correct on any host because it reassembles from bytes rather than aliasing a uint16_t.

Parameters

[in]	buf	Source buffer.
[in]	off_lo	Offset of the low byte; the high byte follows it.

Returns

The reassembled 16-bit value, or zero when buf is NULL.

Return values

0	buf was NULL or the field genuinely reads zero.

Precondition

buf holds at least off_lo + 2 bytes.

off_lo is a header offset from c6_hdr_offset_t.

Postcondition

No buffer byte is modified.

The result is independent of host endianness.

Note

Pure function; safe from any context.

Since

0.1.0

Definition at line 46 of file c6_frame.c.

References k_c6_shift_byte.

Referenced by c6_probe_decode_header().