iCell – Any issues using Reset Pin on a regular basis…

[Rick Reynolds]

I remember reading somewhere that the Reset Pin (hardware reset) should only be used in an emergency. What exactly does this mean? Is there an issue with repeatedly using the reset pin? By repeatedly I mean possibly several times within a 24 hour period. See my scenario below and you’ll understand why I’m asking.

I have been using the SocketCell modems for about three years. We are implementing a second generation of our embedded device and I would like to move us to the iCell line of socket modems.

We had an issue early on with iCell because we couldn’t run in DLE mode as our data would constantly shut down the TCP connection. And, the +++ string to cancel the data connection does not work on the iCell modems.

We have since added access to the modem Reset Pin in order to perform a hardware reset of the modem. This allows me to close the data connection from software without having to worry about DLE mode issues. I am using #PERSISTENTSOCKET and #AUTOCONNECT and get a reconnect very quickly after reset. If I want to perform actions on the modem after reset I simply disable the #PERSISTENTSOCKET function, do my business and then re-enable it. Works great! I really like this functionality as well as the FTP functions for remote software update.

[Rick Reynolds]

Just for clarification… When I referenced SocketCell modems I’m refering to the SocketCell Cell products as opposed to the iCell products.

[Darrik Spaude]

Hi Rick,

The main reason for concern regarding the hardware reset first of all depends on the type of radio (CDMA versus GSM/HSPA), second is in regard to the radio hardware itself, and third is in regard to what the carrier approves.

1) Resetting a CDMA radio while it is receiving an update from the carrier can be bad and may require the radio to be sent in for repair. (see recommendation in #2)

2) Resetting the radio without first properly shutting it down can result in flash memory corruption meaning the radio would need to be replaced. AT#CFUN=0 and waiting for a +WIND response indicating the radio is ready for shutdown is what we recommend.

3) The carriers do not approve products for their networks that circumvent their timers and re-try thresholds. Resetting the device can be seen by the carrier to be a potential area of abuse on their network. We recommend that your application comply with the specific carrier’s requirements.

Based on the above three areas of concern, that is why we recommend that the reset pin only be used in an emergency. We recommend having access and control of the reset pin by your application, but it should be used carefully. If the radio for some reason doesn’t respond for a long period of time, then using the reset pin may be necessary. However, if it is a CDMA modem then just make sure that the device isn’t receiving a update from the carrier. You may have to wait several minutes. Unfortunately the carriers right now can push updates at any time whether or not your application is in a critical state (like sending updates from a medical device to a doctor regarding a patient’s heart condition).

[Rick Reynolds]

Thanks Darrik, that definitely answers my question.

I will implement the AT#CFUN=0 to test for carrier updates in progress.

On 3)… Any idea on a central repositroy of this kind of information? Or do I need to contact each carrier and inquire as to the nature of there timers, re-try thresholds and any other requirements?

Seems like there should be something in place to receive at least an unsolicited message from the carrier before they send an update. Then it would be simple to catch that message and disable resets during that time.

[Darrik Spaude]

Hi Rick,

Sorry for the delay in response. We’ve been waiting for “the list” (of dos and don’ts) from the carriers for quite a while and still have not received it. You would have to try contacting your carrier of choice for such info.

The main issues the carriers have had with customer applications are:

1) For CDMA carriers: Monitor the status of the radio to make sure it is not receiving an update. If receiving an update, then wait for it to finish before resetting the radio.

2) Some carriers have re-dial timers to prevent the radio from attempting to dial too frequently. However, a reset clears that re-dial timer and would allow the radio to re-dial too frequently which could result in a forced loss of service by the carrier.

Best Regards,

Darrik

[Author]

Posts