Configuration¶

Every setting the driver has: T=1 timing, the I2C address and ENA in your port, the ESP32 reference port's options, and the memory the driver uses.

T=1 timing¶

auto& t1 = se.T1();
t1.SetInterFrameDelayMs(3); // wait after each block write before the first read (default 2 ms)
t1.SetReadRetries(10);      // re-read a NACKed or timed-out read this many times (default 6)
t1.SetReadRetryDelayMs(2);  // between those reads (default 2 ms)
t1.SetMaxWtxRequests(16);   // S(WTX) requests accepted in one exchange (default 8)

Setter	Default	Raise it when
`SetInterFrameDelayMs(ms)`	2 ms	The first read after a write keeps failing; some boards need 3 ms
`SetReadRetries(n)`	6	The chip NACKs for longer than retries × delay (slow configurations, low bus speed)
`SetReadRetryDelayMs(ms)`	2 ms	Same; together with retries it bounds how long a read waits
`SetMaxWtxRequests(n)`	8	Long operations (RSA, key generation) end in `Error::Protocol` after many WTX requests
`SetMaxRetransmissions(n)`	3	A noisy bus ends exchanges in `Error::Crc` although single blocks get through
`SetIfsc(n)`	254	Never by hand in normal use: `GetAnswerToReset()` sets it from the SE050's ATR

Each setter has a getter (InterFrameDelayMs(), ReadRetries(), ReadRetryDelayMs(), MaxWtxRequests(), MaxRetransmissions(), Ifsc()). The settings live in the T1Session of each device object and apply to every later exchange.

Address and ENA¶

The I2C address and the ENA pin belong to your port, not the driver. The port on the Porting page takes both in its constructor:

MyI2c i2c_default;                         // 0x48, ENA not wired
MyI2c i2c_on_board(0x48, /*ena_gpio=*/21); // ENA wired to GPIO 21

se050::kDefaultI2cAddress7 is 0x48, the SE050's default target address.

ESP32 reference port¶

The examples' port, hf_se050_examples::HfSe050EspIdfI2c, takes a Se050EspI2cConfig:

Field	Default	Meaning
`port`	`I2C_NUM_0`	ESP-IDF I2C controller
`sda`, `scl`	`GPIO_NUM_47`, `GPIO_NUM_48`	Pins (ESP32-S3 example wiring)
`freq_hz`	`100000`	SCL frequency
`device_address7`	`0x48`	SE050 address
`reset_gpio`	`GPIO_NUM_NC`	GPIO wired to ENA, or not connected

It uses the ESP-IDF v5 i2c_master driver with the internal pull-ups enabled and a glitch filter of 7 clock cycles; see hf_se050_esp_i2c.hpp.

Limits¶

Constant	Value	Meaning
`se050::kMaxApduCommandBytes`	892	Largest C-APDU the builders produce
`se050::kMaxApduResponseBytes`	892	Largest R-APDU buffer the commands use
`se050::t1::kMaxInformationField`	254	INF bytes per T=1 block
`se050::scp03::kWrapScratchBytes`	320	Minimum size of the buffer for `BindScp03WrapScratch()` (short commands)
`se050::scp03::kWrapScratchBytesExtended`	925	Wrap buffer size for any command, extended ones included

Buffers and stack¶

The driver allocates nothing. Commands put their working buffers on the stack of the calling task:

Call	Largest stack buffers
`WriteBinary()`	892-byte C-APDU, 64-byte response
`GetRandom()`, `ReadObject()`, `EcdsaSign()`	892-byte response
Any exchange (`T1Session`)	Two 259-byte block buffers (send and receive)

The deepest call needs about 1.5 kB for these buffers, plus call frames. Data you read goes into buffers you pass, and the SCP03 wrap uses the buffer you bind with BindScp03WrapScratch(), which can live in static memory.

Compile-time¶

There are no configuration macros. se050_version.h, generated at configure time, gives the version (Installation).