Keeping state when awaking from sleep

  • Hi,

    When sleeping other micro controllers (e.g. ATMEL) pick up where they left off, with state mostly the same (ie pin states, memory structures, but usually not the clock - depends on mode). This makes sleeping and saving power easy.

    As the pycom boards seem to restart (ie (re)run and when re-awaking from sleep what are peoples thoughts on maintaining state?

    For example you can use pin.hold([hold])to fix pin state which is good.

    What about variables or state? Use pycom.nvs_set(key, value)? However this can only hold 32 bit ints'.


  • @jcaron thanks, I will keep improving the library.

  • @jcaron thanks

  • @mdk22 A few comments:

    • You should probably store the length separately
    • You should add a (documented) separator between the topic and the index. Otherwise you may end up with collisions when you store thing and thing1 for instance
    • Not sure I figured the reason for the 0x200, but that means you can end up with an overflow

  • @gregcope

    # Written by Mayunk Kulkarni
    import binascii
    from pycom import nvs_set, nvs_get
    class NvsStore():
    #   this class basically stores the string and topic provided in the nvram
    #    given the fact that the string sizes can be variable. Using a variety of
    #    functions to convert string in to int and int back to string we use this
    #    class to store a topic and string in a series of nvram cells
        def __init__(self, topic, stringToStore):
            self.string = stringToStore
            self.topic = topic
            self.__Init(self.string, self.topic)
        def __Init(self, string, topic):
            # step 1: split string into a list of strings each of maximum 4 chars
            # step 2: store the topic and string in the nvram cell and use str2int
            #         to shift each list componenent into nvram
        def str2int(self, string):
            x = binascii.hexlify(string)
            x = int(x, 16)
            x = x + 0x200
            return x
        def store(self, topic):
            # store list values into nvram topic spaces
            for i in range(len(self.strlist)):
                nvs_set(topic+str(i), self.str2int(self.strlist[i]))
        def strSplit(self, string):
            # split string into 4 chars each and put it in a list
            self.strlist = []
            temp = string
            while temp != "":
                if len(temp) < 4 or len(temp) == 4:
                temp = temp[:len(temp)-4]
        def intcount(self, val):
            # old function used for debugging
            y = val
            i = 0
            while int(y/10) != 0:
                y = y / 10
            return i
    class NvsExtract():
    #   This class will be used to extract and return string values back to  
    #   pycom for their use in lora, wifi, LTE services. The topic keys are
    #   constant hence we can find the strings yet we need to use try/except
    #   to catch error for finding limit of a certain topic string
        def __init__(self, topic):
            self.topic = topic
        def __Init(self, topic):
        def extractInt(self, topic):
            # extract integer from nvram topic and put string in self.string
            cnt = 0
            self.string = ""
            x = []
            while True:
                if nvs_get(topic+str(cnt)) == None:
                    cnt += 1
            while len(x) > 0:
                self.string = self.string + x[len(x) -1]
                x = x[:len(x)-1]
            temp = self.string
        def retval(self):
            return self.string
        def int2str(self, integer):
            #convert integer obtained into character string
            integer = integer - 0x200
            integer = hex(integer)
            return binascii.unhexlify(integer[2:])
    test = False
    if test == True:
        NvsStore("ssid", "one")

    Here it is, let me know any suggestions or issues, I am new to this developer community.

  • @mdk22 can you share your lib?

  • I had to create a library myself to save a string of streams in the nvram, along with this, the soft reset option can keep hardware states saved.

  • @jcaron Good point.

  • @gregcope Depending on what you need to save exactly, you can also use the flash file system to save/restore data. Probably not a good idea if you save on each sleep and you wake up often, but for data that does not change too much, it should be a good option.

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