Software Update for new Lidar Lite v3

1

Hello,
I am trying to use new Lidar Lite v3 and I am using PX4 v1.9.2.
With this version of software Lidar probe() function fails because of incorrect reset_sensors() function.
I check the history of the source code and reset_sensors() function changed.
This part of code changed in in this commit: 5eefd94.

Here is the reset_sensors() function:
int
LidarLiteI2C::reset_sensor()
{
px4_usleep(15000);

	int ret = write_reg(LL40LS_SIG_COUNT_VAL_REG, LL40LS_SIG_COUNT_VAL_MAX);

	if (ret != PX4_OK) {
		return ret;
	}

	px4_usleep(15000);
	ret = write_reg(LL40LS_MEASURE_REG, LL40LS_MSRREG_RESET);


	if (ret != PX4_OK) {
		uint8_t sig_cnt;

		px4_usleep(15000);
		ret = read_reg(LL40LS_SIG_COUNT_VAL_REG, sig_cnt);

		if ((ret != PX4_OK) || (sig_cnt != LL40LS_SIG_COUNT_VAL_DEFAULT)) {
			PX4_INFO("Error: ll40ls reset failure. Exiting!\n");
			return ret;

		}
	}

	// wait for sensor reset to complete
	px4_usleep(50000);
	ret = write_reg(LL40LS_SIG_COUNT_VAL_REG, LL40LS_SIG_COUNT_VAL_MAX);

	if (ret != PX4_OK) {
		return ret;
	}

	// wait for register write to complete
	px4_usleep(1000);

	return OK;
}

My question is:
What is the logic behind these changes ? Where these sleeps come from ? How did developers understand that they needed sleep in reset function ? Is there any documentation about reset sequence of lidar lite v3 ?

2

This is the PR where the commit was introduced, it has good information behind the changes, perhaps it helps you understand whats going on.

1 Like
3

Hi rroche,
I saw this PR, but nothing explained about reset logic related changes. They just say new logic properly resets the device. No information provided in device datasheet about these changes.

4

Hey, guys, do you have any idea about the question above @cmic0 @TSC21?

What is the logic behind these changes ? Where these sleeps come from ? How did developers understand that they needed sleep in reset function ? Is there any documentation about reset sequence of lidar lite v3 ?