uart = UART(0, baudrate=115200)

def irq_handler(value):
str1 = str(value) + "\r\n"
uart.write(str1)
value += 1

tim = Timer(0, mode=Timer.PERIODIC)
tim_a = tim.channel(Timer.A, freq=1000)
tim_a.freq(5)

it = 0

tim_a.irq(trigger=Timer.TIMEOUT, handler=irq_handler(it))

But it doesn't work beacouse it sends only first value - '0'. How to solve this problem and what is a difference between this freq: tim_a = tim.channel(Timer.A, freq=1000) and this freq: tim_a.freq(5)?

    self.__alarm = Timer.Alarm(self._seconds_handler, 1, periodic=True)

I've got an error: no such attribute. Does it work on WiPy 1?

tim = Timer(0, mode=Timer.PERIODIC, width = 32)
tim_a = tim.channel(Timer.A|Timer.B, freq=1)
value = 0
tim_a.irq(trigger=Timer.TIMEOUT, handler=irq_handler())

But the discussion is somewhere buried in this board talk:
http://forum.micropython.org/viewforum.php?f=11
Which is anyhow the better place for WiPy 1 question.

And you cannot return a value from an irq handler, unless you modify global symbols or class members. The other question is whether you can allocate memory in that handler, which you do by creating str1. Try to send a constant value first, to see, if it's periodic, and if that succeeds, take the next step.