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alexandClaude Sonnet 5 6d835bc44c Initial import: ESP32 ZiFi32 firmware with SMB2/3 VFS bridge

Based on https://github.com/tslabs/zx-evo/tree/master/pentevo/esp32,
extended with an SMB2/3 server that exposes the ZX Evolution's real SD
card as a network share (browse/download/upload/delete), plus assorted
stability and protocol-correctness fixes in vfs_bridge.cpp and the
vendored libsmb2 - see firmware/README.md for the detailed changelog
and current status.

Also adds:
- firmware/: ready-to-flash compiled binaries + flashing instructions
- hardware/: adapter board connection diagram, PCB photo, and Gerber
  files
- src/third_party/libsmb2: vendored from sahlberg/libsmb2 (LGPL-2.1,
  see its own COPYING/LICENCE files), de-submoduled to a plain
  snapshot with local patches applied directly

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

2026-09-14 16:00:05 +03:00

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ESP32 SPI WiFi

Description

The module is based on ESP32-S2 and provides high-speed WiFi access via SPI bus.

The key-features are:

4-wire 1-bit SPI interface, Slave Mode.
Up to 14Mbit/s data transfer speed.
DMA capable transfers.

Programming

Communication protocol

The SPI Slave communication protocol provides a few types of transactions: READ_REGS, WRITE_REGS, READ_DATA, WRITE_DATA.

READ_REGS

This type of transaction allows reading a number of bytes from the register memory. It can be used to read a register value or a status.

Scenario

Step	Action
1	Assert SPI_CS.
2	Write SPI_DATA with 0x02.
3	Write SPI_DATA with register number.
4	Write SPI_DATA with two dummy bytes.
5	Read one or more bytes from SPI_DATA.
6	De-assert SPI_CS.

Read 1-byte register in C

__sfr __at 0x57 SPI_DATA;
__sfr __at 0x77 SPI_CTRL;
#define SPI_ESP_CS_ON  0x0B
#define SPI_ESP_CS_OFF 0x03

u8 esp_rd_reg(u8 reg_num)
{
  SPI_CTRL = SPI_ESP_CS_ON;
  SPI_DATA = 0x02;
  SPI_DATA = reg_num;
  SPI_DATA;             // dummy
  SPI_DATA;
  u8 rc = SPI_DATA;
  SPI_CTRL = SPI_ESP_CS_OFF;

  return rc;
}

WRITE_REGS

This type of transaction allows writing a number of bytes in the register memory. Not used except for command issuing. Each WRITE_REGS transaction triggers the command execution. Thus, all arguments must be transmitted in the same transaction along with the command.

Scenario

Step	Action
1	Assert SPI_CS.
2	Write SPI_DATA with 0x01.
3	Write SPI_DATA with register number.
4	Write SPI_DATA with one dummy byte.
5	Write SPI_DATA with one or more bytes.
6	De-assert SPI_CS.

Write 1-byte register in C

The following code snippet is just an example not to use. Please refer to 'Write command' snippet for more practical case.

__sfr __at 0x57 SPI_DATA;
__sfr __at 0x77 SPI_CTRL;
#define SPI_ESP_CS_ON  0x0B
#define SPI_ESP_CS_OFF 0x03

void esp_rd_reg(u8 reg_num, u8 reg_value)
{
  SPI_CTRL = SPI_ESP_CS_ON;
  SPI_DATA = 0x01;
  SPI_DATA = reg_num;
  SPI_DATA;              // dummy
  SPI_DATA = reg_value;
  SPI_CTRL = SPI_ESP_CS_OFF;
}

WRITE COMMAND

This is a most used WRITE_REGS case, which triggers a command execution.

Write command in C

The following code snippet is just an example not to use. Please refer to 'Write command' snippet for more practical case.

__sfr __at 0x57 SPI_DATA;
__sfr __at 0x77 SPI_CTRL;
#define SPI_ESP_CS_ON  0x0B
#define SPI_ESP_CS_OFF 0x03

void esp_cmd(u8 cmd)
{
  SPI_CTRL = SPI_ESP_CS_ON;
  SPI_DATA = 0x01;
  SPI_DATA = 0x00;          // ESP_REG_COMMAND
  SPI_DATA;                 // dummy
  SPI_DATA = cmd;           // Command
  SPI_DATA = 0x00;          // Reset status
  SPI_CTRL = SPI_ESP_CS_OFF;
}

READ_DATA

The transaction must only be launched when STATUS register contains DATA_S2M status.

The number of bytes to transfer must be read from xx_SIZE register before the transaction.

Scenario

Step	Action
1	Assert SPI_CS.
2	Write SPI_DATA with 0x04.
4	Write SPI_DATA with three dummy bytes.
5	Read one or more bytes from SPI_DATA.
6	De-assert SPI_CS.
7	Execute `esp_cmd(DATA_END);`

Read a data array in C

__sfr __at 0x57 SPI_DATA;
__sfr __at 0x77 SPI_CTRL;
#define SPI_ESP_CS_ON  0x0B
#define SPI_ESP_CS_OFF 0x03

void esp_recv(u8 *addr, u16 num)
{
  SPI_CTRL = SPI_ESP_CS_ON;
  SPI_DATA = 0x04;
  SPI_DATA; // dummy read means write with 0xFF
  SPI_DATA;
  SPI_DATA;
  while (num--) *addr++ = SPI_DATA;
  SPI_CTRL = SPI_ESP_CS_OFF;
  esp_cmd(ESP_CMD_DATA_END);
}

WRITE_DATA

The transaction must only be launched when STATUS register contains DATA_M2S status.

The number of bytes to transfer must be read or written from/to xx_SIZE register before the transaction.

ATTENTION! When writing data, all transactions must be truncated to 4 bytes. If we need to write 1 byte only, we must write 4 bytes and so on.

To do: add code example.

Registers

All registers are read/writeable from both SPI Master via SPI and Slave firmware. At a low level, they're a shared memory cells inside ESP32 Slave. The total number of registers is 64.

Common registers are COMMAND and STATUS. Registers with addresses 2-63 are used by the ESP32 firmware for different functions depending on a command.

Register summary

Name	Register address, HEX	Size	Description
COMMAND	00	1	Command. Set by Master.
STATUS	01	1	Status of device. Set by Slave while the command is being executed or after its execution. Must be zeroed by Master in the same transaction as the command issued, to ensure the correct synchronization.
PARAM/RESP	02	0..61	If written, must be sent in the same transaction as the command issued. See parameter/response list for individual commands.

STATUS register

Name	Code, HEX	Description
IDLE	00	No status. Must be set by Master along every command issued.
BUSY	01	Device is busy executing a command.
READY	02	Device has completed command execution and is ready for a new command.
ERROR	03	Error happened. Use GET_ERROR command to get the error code.
DATA_M2S	04	Device is ready to receive data from host.
DATA_S2M	05	Device is ready to send data to host.

ERROR register

If a command has been completed with an error, the register 02 automatically indicates error code.

Name	Register address, HEX	Size	Description
ERROR	02	1	Error.

The following table contains error codes.

Name	Code, HEX	Description
NONE	00	No error.
WRONG_PARAMETER	01	Wrong parameter.
INVALID_COMMAND	02	Invalid command.
WRONG_STATE	03	Command cannot be executed in current state.
AP_NOT_CONN	10	Cannot connect AP.
RESET	FE	Is set when reset happened.

Commands

Command summary

Name	Code, HEX	Description
NOP	00	No operation. Issuing this command has no effect.
GET_ERROR		Get extended error info.
GET_INFO	02	Get device info string.
GET_CHIP_INFO	03	Get chip info.
GET_CAPS		Get device capabilities.
GET_HEAP		Get heap size.
GET_NET_CAPS		Get network capabilities.
GET_NETSTATE	11	Get network connection state.
WSCAN	12	Scan Wi-Fi APs.
SET_AP_NAME	13	Set Wi-Fi AP name.
SET_AP_PWD	14	Set Wi-Fi AP password.
GET_AP_NAME	15	Get Wi-Fi AP name.
AP_CONNECT	16	Connect to selected AP.
AP_DISCONNECT	17	Disconnect from AP.
SET_AUTOCONNECT	18	Set AP auto-connect.
GET_IP	19	Get own Wi-Fi IP, net mask, net gateway.
RESOLVE_DNS		Resolve DNS name.
OPEN_UDP
CLOSE_UDP
STATUS_UDP
SEND_DATAGR
RECV_DATAGR
OPEN_TCP
CLOSE_TCP
STATUS_TCP
SEND_TCP
RECV_TCP

SET_WSCAN_PARAMS		Set parameters for Wi-Fi AP scan.

EXT_STATUS_TCP		?
CONF_AUTO_IP		?
CONF_IP		?

DATA_END	D0	End DATA transaction. (A workaround for S3 CMD8 bug).
BREAK	E0	Break an operation.
RESET	EE	Reset device. To be issued in the case of an unpredicted behavior. The reset takes milliseconds to complete. The STATUS register after the reset must contain READY value. The EXT_STAT register must contain RESET value.
GET_RND	F0	Generate random numbers array.
TEST2	F1	Generate tunnel DL for FT812.
TEST3	F2	Generate 3D model DL for FT812.

Miscellaneous commands

GET_INFO

Get device information string. The string is not 0-terminated.

In: none.

Out:

Name	Register address, HEX	Size	Description
INFO_SIZE	02	1	Info string size.

[DATA] - Info string.

GET_CHIP_INFO

Get ESP module hardware parameters.

In: none.

Out: See table below.

Name	Register address, HEX	Size, bytes	Description
CPU_TYPE	02	1	ESP chip type, hex: 02 - ESP32-S3
CPU_CORES	03	1	Number of CPU cores.
CPU_FREQ	04	2	CPU frequency, MHz.
CPU_SI_REV	06	1	Silicon revision.
WIFI	07	1
BLE	08	1
FLASH_SIZE	09	1	Flash size, MB.
FLASH_TYPE	0A	1
FLASH_FREQ	0B	1
PSRAM_SIZE	0C	1	PSRAM size, MB.
PSRAM_TYPE	0D	1
PSRAM_FREQ	0E	1

GET_CAPS

Read device capabilities.

In: none.

Out:

Name	Bit	Mask, Hex	Description

BREAK

Break execution of current command. If no command is being executed, this has no effect.

In: none.

Out: none.

Wi-Fi commands

Most Wi-Fi commands require time to complete. While in progress, the STATUS register indicates BUSY state. It changes to READY upon command completion if successful, or to ERROR, if not.

GET_NETSTATE

Get network state.

In: none.

Out: Network state. See the table below.

Name	Register address, HEX	Size	Description
NETSTATE	02	1	Network state.

NETSTATE

Name	Code, HEX	Description
NETWORK_CLOSED	00	No network connection established.
NETWORK_OPENING	01	Network connection in progress.
NETWORK_OPEN	02	Network connection established.
NETWORK_CLOSING	03	Network disconnection in progress.
NETWORK_UNKNOWN	FF	Network state undefined.

WSCAN

Scan for Wi-Fi APs. Scanned APs are sorted by RSSI, highest first. Requires STATUS register polling to check completion.

In:

Name	Register address, HEX	Size	Description
AP_MAX	02	1	Max number of AP to scan.

Out:

Name	Register address, HEX	Size	Description
AP_TABLE_SIZE	02	2	AP table size.

[DATA] - scanned AP table. See the format below.

Name	Size, bytes	Description
NUM_APS	1	Number of APs scanned.
AP_AUTH	1	AP authorization type.
AP_RSSI	1	AP RSSI, dB.
AP_CHAN	1	AP primary channel
AP_SSID_LEN	1	AP SSID length.
AP_SSID	<AP_SSID_LEN>	AP SSID.
... repeat AP_xx for <NUM_APS>

APn_AUTH

Name	Value, HEX	Description
AP_AUTH_OPEN	00	Open
AUTH_WEP	01
AUTH_WPA_PSK	02
AUTH_WPA2_PSK	03
AUTH_WPA_WPA2_PSK	04
AUTH_EAP	05
AUTH_WPA3_PSK	06
AUTH_WPA2_WPA3_PSK	07
AUTH_WAPI_PSK	08
AUTH_OWE	09
AUTH_WPA3_ENT_192	0A
AUTH_MAX	0B

SET_AP_NAME

Set AP name. 32 bytes max.

In:

Name	Register address, HEX	Size	Description
AP_NAME_LEN	02	1	AP name length.
AP_NAME	03	<AP_NAME_LEN>	AP name.

Out: none.

SET_AP_PWD

Set AP password. 61 bytes max.

In:

Name	Register address, HEX	Size	Description
AP_PWD_LEN	02	1	AP password length.
AP_PWD	03	<AP_PWD_LEN>	AP password.

Out: none.

GET_AP_NAME

Set AP name. 32 bytes max.

In: none.

Out:

Name	Register address, HEX	Size	Description
AP_NAME_LEN	02	1	AP name length.
AP_NAME	03	<AP_NAME_LEN>	AP name.

AP_CONNECT

Connect to the selected AP. Requires STATUS register polling to check completion.

In: none.

Out: none.

AP_DISCONNECT

Disconnect AP. Requires STATUS register polling to check completion.

In: none.

Out: none.

SET_AUTOCONNECT

Enable or disable auto-connect. SET_AP_NAME and SET_AP_PWD must be set before this command.

In:

Name	Register address, HEX	Size	Description
AUTOCONNECT	02	1	Mode: 0 - disabled. 1 - enabled.

Out: none.

GET_IP

Get network IP addresses.

In: none.

Out:

Name	Register address, HEX	Size	Description
IP	02	4	Last DNS resolved IP address.
OWN_IP	06	4	Own IP address.
MASK	0A	4	Net mask.
GATE	0E	4	Net gateway.

RESOLVE_DNS

Resolve IP address from domain name, which length must not be longer than 255 symbols. Requires STATUS register polling to check completion.

In:

Name	Register address, HEX	Size	Description
DNAME_LEN	02	1	Domain name length.
DNAME	03..3F	1..61	Domain name.

If DNAME_LEN<= 61, then it is sent using registers 03-3F. If it is longer than 61 symbols, send the symbols starting from 62 using DATA transaction (currently not supported).

Out:

Same as GET_IP.

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ESP32 SPI WiFi

Description

Programming

Communication protocol

READ_REGS

Scenario

Read 1-byte register in C

WRITE_REGS

Scenario

Write 1-byte register in C

WRITE COMMAND

Write command in C

READ_DATA

Scenario

Read a data array in C

WRITE_DATA

Registers

Register summary

STATUS register

ERROR register

Commands

Command summary

Miscellaneous commands

GET_INFO

GET_CHIP_INFO

GET_CAPS

BREAK

Wi-Fi commands

GET_NETSTATE

WSCAN

SET_AP_NAME

SET_AP_PWD

GET_AP_NAME

**AP_**CONNECT

AP_DISCONNECT

SET_AUTOCONNECT

GET_IP

RESOLVE_DNS

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AP_CONNECT