not sure if this is a bug or known behavior but when I am using the DeviceKey API on mBedOS 6 (I have tested 6.5, 6.7 and 6.11) on my nrf52850 I experience a block of the mbedOS deep sleep functionality of about 67% of the time even though the key was already created.
Does anyone has any idea why this happens or even has a solution? Here is my (simple) example for the test (don´t forget to add “platform.all-stats-enabled”: true to your target_overrides in mbed config):
/*Device Key generation test on mBedOS 6 */
#include "mbed.h"
#include "mbed_stats.h"
#include "DeviceKey.h"
DigitalOut led_green(LED1, 1);
DigitalOut led_red(LED2, 1);
// If key derivation fails hang
void hang()
{
printf("HARDFAULT, hanging\n");
led_red = 0;
while(true) {};
}
// Print an unsigned char buffer in hex format
void print_buffer(unsigned char *buf, size_t size)
{
for (size_t i = 0; i < size; i++) {
printf("%02X", buf[i]);
}
}
// Create/print the device key and salt
int Device_Key_Gen() {
int status = DeviceKey::get_instance().generate_root_of_trust();
if(status == DEVICEKEY_SUCCESS) {
//success
printf("SUCCESS: Root of trust generated!\n");
} else {
//error
printf("INFO: Root of trust not generated! Maybe already exists!\n");
}
DeviceKey &devkey = DeviceKey::get_instance();
unsigned char derive_key1 [DEVICE_KEY_32BYTE];
unsigned char salt1[] = "ch00se_s0m3_salt";
int ret = DEVICEKEY_SUCCESS;
// 32byte key derivation
ret = devkey.generate_derived_key(salt1, sizeof(salt1), derive_key1, DEVICE_KEY_32BYTE);
if (DEVICEKEY_SUCCESS != ret) {
printf("Error, derive key failed with error code %d \n", ret);
return -1;
}
// print device key and salt
printf("Device Key = ");
print_buffer(derive_key1, DEVICE_KEY_32BYTE);
printf("\n");
printf("Salt for key derivation = %s\n", salt1);
return 0;
}
int main()
{
// start
led_green = 1;
led_red = 1;
printf("Device Key...");
if (!Device_Key_Gen() == 0) {
hang();
}
printf("OK\n");
while (true) {
//let the status led blink
led_green = !led_green;
ThisThread::sleep_for(100ms);
led_green = 1;
ThisThread::sleep_for(10s);
//some mbed stats to check sleep status
mbed_stats_cpu_t stats;
mbed_stats_cpu_get(&stats);
printf("Uptime: %llu ", stats.uptime / 1000);
printf("Sleep time: %llu ", stats.sleep_time / 1000);
printf("Deep Sleep: %llu\n", stats.deep_sleep_time / 1000);
}
}
can you also post the logs ? What are the numbers?
You can enable sleep tracking, to find out what is locking the sleep and when. I am browsing the DeviceKey implementation and I can’t spot locking deep sleep there.
Hello Martin, thank you for your response. Sure, here are the logs for the above mentioned code. As you can see in 1, the device is only entering deep sleep for 3.5 (3528ms) seconds / 10 seconds. There is no information in the sleep tracing (see 3) about any process blocking the deep sleep. I was wondering if it might be somehow related to the TRNG keeping the CPU active? The key is generated properly and as far as I understand there should be no other processes running continuously afterwards no?
Using DeviceKey API:
00> Device Key...INFO: Root of trust not generated! Maybe already exists!
00> Device Key = B0CE795XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
00> Salt for key derivation = ch00se_s0m3_salt
00> OK
00> Uptime: 10129 Sleep time: 0 Deep Sleep: 3529
00> Uptime: 20229 Sleep time: 0 Deep Sleep: 7056
00> Uptime: 30329 Sleep time: 0 Deep Sleep: 10585
00> Uptime: 40429 Sleep time: 0 Deep Sleep: 14117
00> Uptime: 50529 Sleep time: 0 Deep Sleep: 17645
00> Uptime: 60629 Sleep time: 0 Deep Sleep: 21174
00> Uptime: 70729 Sleep time: 0 Deep Sleep: 24703
00> Uptime: 80829 Sleep time: 0 Deep Sleep: 28235
00> Uptime: 90929 Sleep time: 0 Deep Sleep: 31763
00> Uptime: 101029 Sleep time: 0 Deep Sleep: 35292
