13 KiB
Protocol
SC64 exposes itself in the system as simple serial device. This allows it to work without manually installed drivers. Serial communication is also well supported in almost all programming languages making it easy to work with. USB protocol use simple packet based communication. Every packet starts with 3 byte identifier and 1 byte data ID. Every argument/data is sent as big-endian value.
Resetting communication
Due to serial communication nature, data transfer between PC and flashcart might get out of sync (for example when long data transfer is aborted before sending/receiving all bytes).
Communication reset is done via emulated DTR/DSR pins.
Start reset procedure by setting DTR pin value to high (1).
Next, observe DSR pin until its state is set to high (1).
At this point communication has been reset and USB interface is disabled. Now it is a good moment to clear/purge any buffers.
Finish reset procedure by setting DTR pin value to low (0) and observe DSR pin until its state is set to low (0).
Flashcart should be ready to accept new commands.
PC -> SC64 packets
| identifier | description |
|---|---|
CMD |
Send command to the SC64 |
SC64 understands only one packet identifier - CMD.
Fourth byte denotes command type listed in supported commands section.
CMD packet
General structure of packet:
| offset | type | description |
|---|---|---|
0 |
char[3] | CMD identifier |
3 |
char[1] | Command ID |
4 |
uint32_t | First argument (arg0) |
8 |
uint32_t | Second argument (arg1) |
12 |
uint8_t[data_length] | Command data (if required) |
CMD packet always require arguments to be sent even if command does not require them.
Arbitrary data length is derived from the argument if specific command supports it.
SC64 -> PC packets
| identifier | description |
|---|---|
RSP |
Success response to the sent command |
ERR |
Error response to the sent command |
PKT |
Asynchronous data packet |
SC64 sends response packet RSP/ERR to almost every command sent from the PC.
Fourth byte is the same as in the command that triggered the response.
If command execution was not successful, then RSP identifier is replaced by the ERR identifier.
SC64 can also send PKT packet at any time as a response to action triggered by the N64 or the flashcart itself.
Fourth byte denotes packet type listed in the asynchronous packets section.
RSP/ERR packets
General structure of packet:
| offset | type | description |
|---|---|---|
0 |
char[3] | RSP/ERR identifier |
3 |
char[1] | Command ID |
4 |
uint32_t | Data length |
8 |
uint8_t[data_length] | Response data (if any) |
RSP/ERR packet is sent as a response to the command sent by the PC.
ERR response might contain no (or undefined) data in the arbitrary data field compared to regular RSP packet.
PKT packet
General structure of packet:
| offset | type | description |
|---|---|---|
0 |
char[3] | PKT identifier |
3 |
char[1] | Asynchronous packet ID |
4 |
uint32_t | Data length |
8 |
uint8_t[data_length] | Packet data (if any) |
Available packet types are listed in the asynchronous packets section.
Supported commands
| id | name | arg0 | arg1 | data | response | description |
|---|---|---|---|---|---|---|
v |
IDENTIFIER_GET | --- | --- | --- | identifier | Get flashcart identifier SCv2 |
V |
VERSION_GET | --- | --- | --- | version | Get flashcart firmware version |
R |
STATE_RESET | --- | --- | --- | --- | Reset flashcart state (CIC params and config options) |
B |
CIC_PARAMS_SET | cic_params_0 | cic_params_1 | --- | --- | Set CIC emulation parameters (disable/seed/checksum) |
c |
CONFIG_GET | config_id | --- | --- | current_value | Get config option |
C |
CONFIG_SET | config_id | new_value | --- | --- | Set config option |
a |
SETTING_GET | setting_id | --- | --- | current_value | Get persistent setting option |
A |
SETTING_SET | setting_id | new_value | --- | --- | Set persistent setting option |
t |
TIME_GET | --- | --- | --- | time | Get current RTC value |
T |
TIME_SET | time_0 | time_1 | --- | --- | Set new RTC value |
m |
MEMORY_READ | address | length | --- | data | Read data from specified memory address |
M |
MEMORY_WRITE | address | length | data | --- | Write data to specified memory address |
U |
USB_WRITE | type | length | data | N/A | Send data to be received by app running on N64 (no response!) |
D |
DD_SET_BLOCK_READY | success | --- | --- | --- | Notify flashcart about 64DD block readiness |
W |
WRITEBACK_ENABLE | --- | --- | --- | --- | Enable save writeback through USB packet |
p |
FLASH_WAIT_BUSY | wait | --- | --- | erase_block_size | Wait until flash ready / Get flash block erase size |
P |
FLASH_ERASE_BLOCK | address | --- | --- | --- | Start flash block erase |
f |
FIRMWARE_BACKUP | address | --- | --- | status/length | Backup firmware to specified memory address |
F |
FIRMWARE_UPDATE | address | length | --- | status | Update firmware from specified memory address |
? |
DEBUG_GET | --- | --- | --- | debug_data | Get internal FPGA debug info |
% |
STACK_USAGE_GET | --- | --- | --- | stack_usage | Get per task stack usage |
v: IDENTIFIER_GET
Get flashcart identifier SCv2
This command does not require arguments or data.
response (identifier)
| offset | type | description |
|---|---|---|
0 |
char[4] | Identifier |
Identifier is always SCv2 represented in ASCII code.
V: VERSION_GET
Get flashcart firmware version
This command does not require arguments or data.
response (version)
| offset | type | description |
|---|---|---|
0 |
uint16_t | Major version |
2 |
uint16_t | Minor version |
4 |
uint32_t | Revision |
Increment in major version represents breaking API changes.
Increment in minor version represents non breaking API changes.
Increment in revision field represents no API changes, usually it's denoting bugfixes.
R: STATE_RESET
Reset flashcart state (CIC params and config options)
This command does not require arguments or data.
This command does not send response data.
B: CIC_PARAMS_SET
Set CIC emulation parameters (disable/seed/checksum)
arg0 (cic_params_0)
| bits | description |
|---|---|
[32:25] |
Unused |
[24] |
Disable CIC |
[23:16] |
CIC seed (IPL2 and IPL3 stages) |
[15:0] |
Checksum (upper 16 bits) |
arg1 (cic_params_1)
| bits | description |
|---|---|
[31:0] |
Checksum (lower 32 bits) |
This command does not send response data.
t: TIME_GET
Date/time values use the BCD format.
This command does not require arguments or data.
response (time)
| offset | type | description |
|---|---|---|
0 |
uint8_t | Weekday (1 - 7), 1 represents Monday |
1 |
uint8_t | Hours (0 - 23) |
2 |
uint8_t | Minutes (0 - 59) |
3 |
uint8_t | Seconds (0 - 59) |
4 |
uint8_t | Unused (returns zero) |
5 |
uint8_t | Year (0 - 99) |
6 |
uint8_t | Month (1 - 12) |
7 |
uint8_t | Day (1 - 31) |
T: TIME_SET
Date/time values use the BCD format.
arg0 (time_0)
| bits | description |
|---|---|
[31:24] |
Weekday (1 - 7), 1 represents Monday |
[23:16] |
Hours (0 - 23) |
[15:8] |
Minutes (0 - 59) |
[7:0] |
Seconds (0 - 59) |
arg1 (time_1)
| bits | description |
|---|---|
[31:24] |
Unused |
[23:16] |
Year (0 - 99) |
[15:8] |
Month (1 - 12) |
[7:0] |
Day (1 - 31) |
This command does not send response data.
Asynchronous packets
| id | name | data | description |
|---|---|---|---|
B |
BUTTON | --- | Button on the back of the SC64 was pressed |
G |
DATA_FLUSHED | --- | Data from USB_WRITE command was discarded |
U |
DEBUG_DATA | debug_data | Data sent from the N64 |
D |
DISK_REQUEST | disk_info/block_data | 64DD disk block R/W request |
I |
IS_VIEWER_64 | text | IS-Viewer 64 printf text |
S |
SAVE_WRITEBACK | save_contents | Flushed save data |
F |
UPDATE_STATUS | progress | Firmware update progress |