modem_info_short_get fails

[Andrea]

Same as Case ID: 234629  .

Calling modem_info_short_get for the parameters MODEM_INFO_MCC and MODEM_INFO_MNC fail.

I suspect the problem is in code. Tracing the MCC call shows that the call makes the correct AT query to the modem. However, the parameter returned is (rightly) a string. However the value expected for that parameter is a short so the call fails. Trying to call modem_info_string_get fails because the value is typed as a short in the parameter array.

This new ticket is to confirm that it fails on NCS 1.1.0 with modem firmware 1.1.0.

[Øyvind]

Hello, 

Can you please provide information on what fails? How are you calling the function? What error message are you getting? I will need more information to find the root cause. 

Thanks! 

Kind regards,
Øyvind

[Andrea]

modem_info_short_get(MODEM_INFO_MCC, &mcc) returns -EINVAL.

We have already told you what the root cause is. MODEM_INFO_MCC expects a short but the modem returns a string.

If you write a unit test you can easily reproduce the issue.

[Andrea]

First line of my reply. I've just called the function and it returned EINVAL.

I have worked around the issue by implementing the AT response parser myself.

[Øyvind]

Listen, you are probably correct, but you aren't giving me much to work with here. 

From modem_info.h

/** @brief Request the current modem status of any predefined
 *         information value as a short.
 *
 * If the data parameter returned by the modem is originally a
 * string, this function fails.
 *
 * @param info The requested information type.
 * @param buf  The short where to store the information.
 *
 * @return Length of received data if the operation was successful.
 *         Otherwise, a (negative) error code is returned.
 */
int modem_info_short_get(enum modem_info info, u16_t *buf);

From modem_info.c

int modem_info_short_get(enum modem_info info, u16_t *buf)
{
	int err;
	char recv_buf[CONFIG_MODEM_INFO_BUFFER_SIZE] = {0};
	int cmd_length = 0;

	if (buf == NULL) {
		return -EINVAL;
	}

	if (modem_data[info]->data_type == AT_PARAM_TYPE_STRING) {
		return -EINVAL;
	}

	err = at_cmd_write(modem_data[info]->cmd,
			   recv_buf,
			   CONFIG_MODEM_INFO_BUFFER_SIZE,
			   NULL);

	if (err != 0) {
		return -EIO;
	}

	err = modem_info_parse(modem_data[info], &recv_buf[cmd_length]);

	if (err) {
		return err;
	}

	err = at_params_short_get(&m_param_list,
				  modem_data[info]->param_index,
				  buf);

	if (err) {
		return err;
	}

	return sizeof(u16_t);
}

There are two if statements that return -EINVAL

Have your verified that your data_type == AT_PARAM_TYPE_NUM_SHORT?

[Andrea]

The EINVAL is returned from lib/modem_info/modem_info.c:422.

err = at_params_short_get(&m_param_list,
modem_data[info]->param_index,
buf);

Look at lib/at_cmd_parser/at_params.c:264

if (param->type != AT_PARAM_TYPE_NUM_SHORT) {
		return -EINVAL;
	}

The code looks for a short but finds a string and returns EINVAL. When I call modem_info_short_get(MODEM_INFO_MCC, &mcc) param->type is 3.

To confirm this is the problem, if I change lib/modem_info/modem_info.c:173 from:

.data_type = AT_PARAM_TYPE_NUM_SHORT,

to

.data_type = AT_PARAM_TYPE_STRING,

it works.

This is consistent with AT commands reference:

infocenter.nordicsemi.com/.../cops_read.html

[Øyvind]

Thanks for pointing this out to us. I have now forwarded this to our NCS team, and they confirm the issue. 

Have a great day!

[Jan Tore Guggedal]

Hi Andrea,

Thanks for reporting the issue.

If I understand correctly what you're trying to achieve, it seems you would rather read out MODEM_INFO_OPERATOR instead and get the concatenated MCC and MNC string that you refer to in the AT command reference. Changing .data_type to AT_PARAM_TYPE_STRING would read out the same operator string for both MODEM_INFO_OPERATOR, MODEM_INFO_MCC, and MODEM_INFO_MNC.

To have MCC and MNC as numeric values, some more parsing has to be done. This is actually done under the hood if you call modem_info_params_get(). Then the .mcc.value and .mnc.value fields of the modem_param_info struct are populated correctly with numeric values. I know, it's inconvenient to have to use this giant struct instead of reading it out directly, but unfortunately that's the only way to do it in today's codebase.

Best regards,
Jan Tore