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CELL215 observations and questions following evaluation of a demo unit


artyb Jul 20, 2020 05:26 AM

Hi,

I recently evaluated a CELL215 and had some issues and suggestions.

It’s quite a complicated piece of kit, with lots of different ways it can be used (CS I/O or RS232) and on CR1000X type loggers vs CR1000 era, so there were lots of things to try which is quite time consuming. The modem was supplied with the latest OS and no module firmware OTA update was offered during the evaluation time.

I did run into some issues, some of which I wasn’t able to resolve, and some of which stopped the modem from working, and have some suggestions too. I’ve tried to capture some debug info for some of the issues.

I found it easier to work with in integrated mode CR1000X series, which is the future, but we will continue seeing clients wanting to reuse CR1000 loggers for some time.

I was hoping it would function very well with the loggers, and be able to easily report signal strength in use. I like the low power specs with 4G CAT 1 and 3G and 2G fallback.

Unfortunately I couldn’t start using these at present due mainly to the issues I found (unless these issues can be resolved) and also it is a higher cost item than some alternatives.

If the support responses or any OS changes are made which resolve the issues I experienced I’d certainly review that.

Thanks in advance,
A

Issues/suggestions summary (I have some saved screenshots, film of the flash pattern and log files etc which might help in debugging some of these issues which I could provide). I'll number these points for clarity:

 

1) Seems to work better with CR1000X than CR1000 (programming is much more verbose for CR1000 via terminal mode with CS I/O SDC connection).

2) I couldn’t get the modem to stay in deep sleep mode which is necessary for power saving with CS I/O and CR1000 (https://www.campbellsci.com/forum?forum=1&l=thread&tid=16322 reports the same issue, without response). The modem enters the deep sleep mode, then wakes up and redials, both with and without the web interface/USB lead. If I had to use RS232 connection in order to control power, then the potential benefits of being able to monitor the signal and modem state etc are lost.

3) Are reboot commands advisable if the modem isn’t being power cycled (deep sleep being used)-no examples of this? Is a software reboot as effective a reset as a power cycle?

4) The web interface loses the ‘Access Technology’ setting frequently (goes to 2G from Automatic, but maybe that doesn’t make any difference unless a particular network is specified?).

5) Is there a need for username/password for the web interface-this aspect seems incomplete?

6) Modem frequently stopped responding in non-integrated PPP mode with CR1000 and using the SDC terminal interface and does an undocumented flash pattern (3 blue, then 2 red approx once per second), plugging in USB resolved it only until USB removed. Don't know what this means or how to stop it.

7) It would be good to be able to save config from web interface for record keeping and traceability (especially if the modem serial number were also saved) and to be able to load a saved configuration for speed and consistency.

8) Unclear about diversity aerial function/need. Is it only 4G, and to increase download speed via MIMO or can it improve reception? (The newer manual is a bit more helpful on this than the earlier one I was mainly following).

9) Example program has typos in it (couple of Publicc) and unhelpfully changes the interface port from SDC8 to SDC7.

10) I didn’t find any way to refresh RSRQ and RSSI from the datalogger? eg to use to align aerial? Unclear how often these update, seems to be at least minutes? Web interface seems to cause refresh of values.

11) Logger in integrated mode reports different signal strength values to web interface (4G mode  both cell_rssi and cell_rsrp report the rsrp value on the web interface). Section 7.3 of the manual may allude to this? “For 3G networks, this is reported as RSSl (Received Signal Strength Indicator). For 4G, it is RSRP (Reference Signal Received Power)”.

12) Web interface didn’t show the present time, concerned that without that any settings in the modem for automatic power cycle may fail?

13) Unclear to me when serial server or client modes would be used?

14) Parsing the status response strings in integrated mode isn’t as easy as it could be as the number and placement of items varies depending on the modem state. Some examples of how to do this would be useful. I developed some code using an array of header values to pick out from the array of responses, but this all takes time, and adds to the complexity of the program needed, rather than just being able to pick out the nth element of an array for example.

15) Data SIMS are more commonly mini (2FF), and those that support micro (3FF) often snap out to nano (4FF) as well. The nano SIM could get lost in the field more easily?

16) I gather that 4G signal testers don’t cover CAT 1 specifically, but that if regular 4G is present CAT 1 can be assumed to be.


JDavis Jul 21, 2020 09:33 AM

1) There is no longer space in the OS chip on the CR1000 to store any more features. It just is not possible to make it as easy on the CR1000 as it is on the newer CR1000X.

2) A cell modem update is in the works relating to this issue. The CR1000 actually keeps talking for a while after sending the deep sleep command. The planned OS change will make the modem ignore the talk, until it receives the proper command to wake back up.

3) A simple thing to do is a daily soft reboot. That is generally more than necessary. The proper advice for a modem that will be always powered is to reboot is communication stops working for a period of time. For example, if it has been an hour since you were last able to ping google, reboot the modem. I have seen some cases in the past with third party modems where network-side issues would make you lose connection after about 2 weeks. The keep alive ping setting in the modem is designed for this scenario.

5) If using a static/public cellular account, and accessing the web interface over the air, a username and password is needed to change settings. When you have physical access to plug directly in, the username and password are not needed.

8) 4G networks now expect you to have diversity antennas. Having the second antenna won't increase your throughput on a CAT 1 modem, but it will improve your signal quality and connection reliability. In the US, we have already see sites where connections are not stable on these modems with a single antenna where cell towers now have 5G equipment. Please use two antennas (or a combined MIMO antenna) at all new sites.

10) For antenna alignment, it is recommended to use the web interface of the modem. That can be manually refreshed. Otherwise, you would need to write a datalogger program that requests signal strength more often than you normally would.

13) Serial client would be for cases where you have a piece of equipment without PPP capability. Serial server is for similar situations, but only valid if you have an account with static IP address.

15) Hands are tied as far as SIM size. The CAT 1 cellular modules are small, so they use a small SIM size. At least you should only need to handle the SIM when setting up a new modem (usually done in the office) or switching cellular providers.

16) If the signal tester shows you strength per band, it would be valid for CAT 1 modems. Some of the 4G bands in the area might not be supported by the CAT 1 modems. Look at the strength on the bands the modem supports.


artyb Jul 22, 2020 11:16 AM

Hi,

Thank you for the reply. Some responses:

1) Useful to understand the reason. Things have to move on!

2) Good to know it is an acknowledged issue, shame I spent a lot of time trying to get this to work...

3) OK, Perhaps adding example code would save people inventing this themselves. Is a soft-reboot as thorough as a power-cycle?

5) I see. I hadn't picked up from the manual on being able to access the web interface remotely. What IP address would be neeed?

8) OK. So there is some additional cost. Useful to know that the reason isn't just to increase speed, which isn't neeed. Not sure what spacing would be best, as it varies with signal type?

10) That could work I suppose, with someone remote reading out values to a crew onsite. Maybe not as easy as being able to read the values themselves with the display though. I was trying writing programs to read the signal strength values more frequently than normal, but they didn't change even when I deliberately blocked the signal. I don't know what the update interval is.

13) Your reply sounds counter-intuitive? If the equipment lacked PPP then wouldn't the modem need to be in PPP mode? Some examples in the manual might help users?

15) Understood. Progress!

16) Yes, that's clear thank you.

Best Wishes,
A

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