@jmarcelino What is the right voltage a for that pin? What is the amperage required for the modem?

@jmarcelino That fixed the problem! I did not have a jumper on the RX pins. By demo application I mean that when I plug in the board the green LED flashes, followed by the blue LED every 4 seconds. Thanks a lot for your help!

@seb A) FiPy+PyTrack+LiPo-Battery (Not-Attached-to-USB3.0) 
Vin = 4.09~4.10 V 3V3 = 3.32 V B) PyTrack+USB-Serial-device (Attached-to—USB3.0) same port as A)
 Vin = 4.85 V 3V3 = 0.23 V C) PyTrack+USB-Serial-device (Attached-to—USB3.0) + Hotswap-in-FiPy same port as A) & B)
 Vin = 4.55 V 3V3 = 3.32 V D) PyTrack+FiPy+NO-USB-Serial-device (Attached-to—USB3.0) same port as A) & B) & C) same combo as C) Just unplugged USB from PyTrack, and re-attached it…
 Vin = 1.69~2.51 V 3V3 = 1.15~1.91 V Also, worth nothing is that if my hand slips with the measuring probes, I get it to “boot-up” by accidentally shorting GROUND & 3V3, and I get a USB-Serial-Devices on my computer [ergo like A), B) & C) …] … And then, I get the same Vin & 3V3 as C) Which makes me conclude that you’ve guys have a Firmware issue!!! … and not a “bad usb-cable” or “bad usb-port” … etc etc. For some reason, in the boot-sequence of the PyTrack Firmware, it choose not to boot-up FiPy and enable USB-Serial … And, again, it’s odd that I can short GROUND & 3V3 with my measuring probes, and then it boots up FiPy and enables USB-Serial…

@marto Hi thanks for pointing that you, you are correct the updater tool only shows instructions for the expansion board at the moment. I have passed this on and it should hopefully be changed soon. I will now remove the text about carefully reading the updater instructions because that clearly caused confusion. I will also pass on your OS details so make sure it gets investigated at the same time as the Mac OS issues.

Can you please first try another firmware update (we have released 1.10.2.b1). If that doesn't help please try to format the internal flash: import os; os.mkfs('/flash') If that still doesn't help please email support@pycom.io

@jorismathijssen Hi Joris. Did you tried tot upload thé firmware again? Be sure to powercycle your device. Did you run dfu utils with elevated rights? (Admin on Windows of sudoku on Linux?) Good luck

@robert-hh Thanks a lot, Man! Works like a charm. :) Now I get where I was wrong! I was measuring pulses the wrong way. Moreover, I wasn't resetting the self.start variable..!! :'D Thank You, Devang.

@robert-hh Thank you, that did it (Setting the single connection only).

@livius Yes this is a fresh boot with nothing in boot.py or main.py, no extra code is running. Even importing just the requested module still blows up memory. >>> import gc;gc.mem_free() 65056 >>> from urllib.parse import unquote Traceback (most recent call last): File "<stdin>", line 1, in <module> File "/flash/lib/urllib/parse.py", line 475, in <module> File "/flash/lib/urllib/parse.py", line 475, in <dictcomp> MemoryError: memory allocation failed, allocating 2344 bytes >>> All is good though. I found a module written for WiPy 1.0 that has worked around the memory issues. The problem still needs to be fixed in uPython mainline libraries, but this workaround works for me. >>> from urllib import unquote >>> unquote('abc%20def') 'abc def' >>>

@tobru From memory I think it was a 10k resister - check the spec sheet for the HC-SR04. I probably just attached it straight onto the expansion board, maybe via a breadboard - I can't remember sorry.

Ah derp. yeah that works. I'm new to (micro)python & coding for hardware, so learning lots at the moment. Thanks.

@Ralph Thanks a lot for your quick answer. i will keep going with rshell.

@jmarcelino '1.6.12.b1'

If you are looking for simple REPL through telnet I can recommend you to check out my Python script: link Easiest way to get started :) If you want to write scripts for your device, like main.py (a.k.a. modules) then you can do so in your favorite code editor and upload through ftp.