rng90.c File Reference

Implementation of the RNG90 driver functions. More...

#include "rng90.h"

Include dependency graph for rng90.c:

Functions
RNG90_SelfTest_Status	rng90_selftest (RNG90_Run_SelfTest test)
	Initializes the RNG90 device by running a self-test.
RNG90_Status	rng90_info (RNG90_Info *info)
	Requests device information from the RNG90 and fills an info structure.
RNG90_Status	rng90_random (unsigned char *numbers)
	Requests random numbers from the RNG90 device and stores them in a buffer.
RNG90_Status	rng90_serial (unsigned char *serial)
	Reads the device serial number from the RNG90 and stores it in a buffer.

Variables
unsigned char	rng90_buffer [87]

Detailed Description

Implementation of the RNG90 driver functions.

This file contains the implementation of functions to initialize the RNG90 device, perform self-tests, retrieve device information, generate random numbers, and read the device serial number. It utilizes TWI/I2C communication to interact with the RNG90 hardware.

Author

g.raf

Date

2026-01-25

Version

1.0 Release

Copyright

Copyright (c) 2026 g.raf Released under the GPLv3 License. (see LICENSE in repository)

Note

This file is part of a larger project and subject to the license specified in the repository. For updates and the complete revision history, see the GitHub repository.

See also

https://github.com/0x007e/drivers-crypto-rng90 "RNG90 crypto driver library"

Function Documentation

rng90_info()

RNG90_Status rng90_info

(

RNG90_Info *

info

)

Requests device information from the RNG90 and fills an info structure.

Parameters

info	Pointer to an RNG90_Info structure that will be populated with the following fields if the command completes successfully: RFU DeviceID SiliconID Revision

Returns

Returns one of the following status codes:

• RNG90_Status_Success if a valid info response was received and info was filled.
• RNG90_Status_SelfTest_Error (cast from the buffer) if the response is a self-test status frame.
• RNG90_Status_Other_Error if the response frame is invalid, has an unexpected length, or another communication/parse error occurred.

This function requests device information from the RNG90 and evaluates the returned frame. Depending on the response type, it either interprets the first data byte as a self-test status or extracts the identification fields into info and returns an appropriate status code.

Here is the call graph for this function:

rng90_random()

RNG90_Status rng90_random

(

unsigned char *

numbers

)

Requests random numbers from the RNG90 device and stores them in a buffer.

Parameters

numbers

Pointer to a buffer where the received random bytes will be stored.

Warning

The buffer must be able to hold at least RNG90_OPERATION_RANDOM_RNG_SIZE bytes.

Returns

Returns one of the following status codes:

• RNG90_Status_Success if valid random data was received and written to numbers.
• RNG90_Status_TWI_Error if a TWI/I2C transmission error occurred while sending the command or payload.
• RNG90_Status_SelfTest_Error (cast from the buffer) if the response is a self-test status frame instead of random data.
• RNG90_Status_Other_Error if the response frame is invalid, has an unexpected length, or another communication/parse error occurred.

This function sends a random-number request to the RNG90 device, transmits the associated payload and CRC over TWI/I2C, and then reads back the response frame. Depending on the response type, it either copies the received random bytes into numbers or returns an appropriate status code.

Here is the call graph for this function:

rng90_selftest()

RNG90_SelfTest_Status rng90_selftest

(

RNG90_Run_SelfTest

test

)

Initializes the RNG90 device by running a self-test.

Returns

Returns one of the following status codes:

• RNG90_Status_Success if the DRBG self-test completed successfully and the device is ready for operation.
• RNG90_Status_SelfTest_Error if the DRBG self-test failed and the device should not be used.

This function performs an initialization sequence for the RNG90 device by invoking the rng90_selftest() routine with RNG90_Run_DRBG_SelfTest to verify the deterministic random bit generator (DRBG) functionality. If the self-test does not report RNG90_SelfTest_Success, the function returns RNG90_Status_SelfTest_Error to indicate that the device failed initialization. When the DRBG self-test completes successfully, the function returns RNG90_Status_Success`, signaling that the RNG90 is ready for normal operation. */ RNG90_Status rng90_init(void) { if(rng90_selftest(RNG90_Run_DRBG_SelfTest) != RNG90_SelfTest_Success) { return RNG90_Status_SelfTest_Error; } return RNG90_Status_Success; }

static void rng90_write(RNG90_Packet *packet) { unsigned char *ptr = (unsigned char *)packet; packet->count += 7;

crc16_init( 0x0000 );

twi_address( 0x40 , TWI_Write); twi_set( 0x03 );

for (unsigned char i=0; i < (sizeof(RNG90_Packet) - 2UL ); i++) { crc16_update(*(ptr + i)); twi_set(*(ptr + i)); } }

static void rng90_command(RNG90_Packet *packet) { twi_start(); rng90_write(packet);

packet->crc = crc16_result();

twi_set((unsigned char)(0x00FF & packet->crc)); twi_set((unsigned char)(0x00FF & (packet->crc>>8))); twi_stop(); }

static RNG90_Frame rng90_frame;

static RNG90_Frame rng90_data(unsigned char *data) { crc16_init( 0x0000 );

unsigned char temp = 0; unsigned int crc = 0x0000;

rng90_frame.length = 1 + 2UL ; rng90_frame.status = RNG90_Data_Status_Invalid;

twi_start(); twi_address( 0x40 , TWI_Read);

for (unsigned char i=0; i < rng90_frame.length - 2UL ; i++) {
twi_get(&temp, TWI_ACK); crc16_update(temp);

if(i == 0) { rng90_frame.length = temp; continue; } (data + i - 1) = temp; }

twi_get(&temp, TWI_ACK); crc = (0x00FF & temp); twi_get(&temp, TWI_NACK); crc |= (0xFF00 & (temp<<8));

twi_stop();

rng90_frame.status = RNG90_Data_Status_Valid;

if (crc != crc16_result()) { rng90_frame.status = RNG90_Data_Status_Invalid; } return rng90_frame; }

/**

Executes a self-test routine on the RNG90 device.

Parameters

test	Specifies which self-test to run, using a value from RNG90_Run_SelfTest: RNG90_Run_DRBG_SelfTest RNG90_Run_SHA256_SelfTest RNG90_Run_DBRG_SHA256_SelfTest

Returns

Returns one of the following self-test status codes:

• RNG90_SelfTest_Success if the requested self-test completed successfully.
• RNG90_SelfTest_Fail_DBRG if the DRBG self-test failed.
• RNG90_SelfTest_Fail_SHA256 if the SHA-256 self-test failed.
• RNG90_SelfTest_Fail_DBRG_SHA256 if both DRBG and SHA-256 self-tests failed.
• RNG90_SelfTest_Not_Run_DBRG, RNG90_SelfTest_Not_Run_SHA256, or RNG90_SelfTest_Not_Run_Neither if one or more tests were not executed.
• RNG90_SelfTest_Error if the response frame is invalid or a general error occurred.

This function triggers a self-test on the RNG90 device according to the selected test mode and evaluates the returned status code. Depending on the self-test result, an appropriate RNG90_SelfTest_Status value is returned to the caller.

Here is the call graph for this function:

rng90_serial()

RNG90_Status rng90_serial

(

unsigned char *

serial

)

Reads the device serial number from the RNG90 and stores it in a buffer.

Parameters

serial

Pointer to a buffer where the received serial number bytes will be stored.

The buffer must be able to hold at least RNG90_OPERATION_READ_SERIAL_SIZE bytes.

Returns

Returns one of the following status codes:

• RNG90_Status_Success if a valid serial number frame was received and serial was filled.
• RNG90_Status_SelfTest_Error (cast from the buffer) if the response is a self-test status frame instead of serial data.
• RNG90_Status_Other_Error if the response frame is invalid, has an unexpected length, or another communication/parse error occurred.

This function sends a read command to the RNG90 device to obtain its serial number. After the command has been processed, the response frame is evaluated. If valid serial data is returned, the bytes are copied into serial and an appropriate RNG90_Status value is returned.

Here is the call graph for this function:

Variable Documentation

rng90_buffer

unsigned char rng90_buffer[87]