[chbot] [random, but interesting (RBI)] LoraWAN: Extremely long range, low power wireless communication

Mon Jan 8 21:16:38 GMT 2018

The early boards based on the ESP32 (WiPy2, LoPy, FiPy, etc) had two 
design faults and could not achieve the claimed 10 uA deep-sleep 
current [1] [2]. Pycom issued a separate plug-in board and a library 
that brings the deep-sleep power down to 7--10 uA depending on the 
wake-sources configured: timers or GPIO interrupts. Note that I have 
not actually measured this deep-sleep power.

The ESP32 does not have the low-power peripherals that some of the 
low-power ARM-core devices have: STM32 from ST or EFM32 from Silabs. 
They have low-power UARTs (limited speed), timers, PWMs, capactive 
sensors, and so on, as well as convenient ways for various peripherals 
to trigger one another without waking the processor core.

In one application, we had a GPIO pin monitoring the RX line of a UART; 
the GPIO was connected to a hardware timer. Any activity on the RX line 
would keep resetting the timer. When the timer reached a certain count 
(line idle), it would activate a different GPIO to enable a line 
driver, then at a slightly later count, trigger a DMA controller that 
would feed a sequence of bytes to the UART. When the last byte had been 
sent, another hardware timer would start, and disable the line driver 
when it timed out. It took a bit of setting up to program the GPIOs, 
timers, DMA controllers, UARTs and event sequencer, and prepare the 
message to send, but after it had been set up, the system did it all 
without intervention from the processor.

Stephen Irons

[1] The GPIO pin that was meant to put the switching supply into a 
low-power mode was not in the RTC power domain and so was not usable in 
deep-sleep mode. The pin did not drive to the correct state, leaving 
the power supply in its high-performance mode, consuming ~10 mA.

[2] The chip select for the flash chip floats in the low-power, leaving 
the flash enabled, consuming ~2.5 mA.

On Mon, 8 Jan, 2018 at 7:14 PM, Mike Field <hamster at snap.net.nz> wrote:
> Strange you should mention PyCom.
> 
> Today I received a baseboard (USB serial bridge, battery controller, 
> uSD socket, and a few extras) and WiPy (ESP32 module incl WiFi and 
> Bluetooth broken out to 0.1" headers) from the LTE Team Lead at PyCom 
> who wanted to brag at the excellent low power during sleep - yet to 
> test, but should be well under 50uA.
> 
> The PyFi boards look amazingly well made, arel fully certified and 
> extreme well presented, in nice plastic cases with magnetic closures, 
> and plenty of ESD foam. Made a very great first impression so much I 
> am going to be nice to it!
> 
> At the same time I also got a $8 LOLIN32 Pro (ESP32, uSD socket, USB 
> bridge LiPo mgmt also with MicroPython), in a yellow aliexpress 
> envelope, with an antistatic bag, and headers I have to solder on. 
> But what more can I expect for the price?
> 
> Looking forward putting them both through their paces over the next 
> few days as they have a very comparable freature set. The only 
> difference might be the PCB antenna vs the ceramic antenna on the 
> more expensive PyFi module, and the better power setup on the 
> baseboard. It might also be fully tricked out with flash ROM.
> 
> If anybody is nterested in evaluatiing (a.k.a. 'play with') either of 
> them, ping me an email...
> 
> Mike
> 
> 
> -------- Original Message --------
> Subject: Re: [chbot] [random, but interesting (RBI)] LoraWAN: 
> Extremely long range, low power wireless communication
> From: Stephen Irons
> To: Christchurch Robotics
> CC: Christchurch Robotics
> 
> 
>> In case you want to play around with LoRaWAN, https://pycom.io/ sell
>> the 'LoPy', which gives you a LoRa modem and an ESP32 processor, 
>> with a
>> MicroPython interpreter. So you write your application in MicroPython
>> (Python3, almost the complete language, but with only a limited set 
>> of
>> libraries), and you have LoRa, LoRaWAN, Wi-Fi and Bluetooth
>> connectivity, with rapidly improving libraries for using the ESP32
>> hardware devices for SPI, I2C, PWM, etc.
>> 
>> We developed a system for a client using the LoRa modem (the
>> spread-spectrum modulation) for short-ish-range communication through
>> bush, where its performance at low signal levels works well for us. 
>> We
>> do not use the whole LoRaWAN stack, as there is no LoRaWAN
>> infrastructure in our client's trial areas (remote Marlborough Sounds
>> and Haast), though Telecom was happy to set up a trial network for us
>> to test. It all worked fine, but battery life of the base station was
>> an issue; we needed a solar panel to provide enough power, and we 
>> have
>> had bad experiences with solar panels in the bush, where dead leaves
>> and general muck block the panel. So we would also need a mast to get
>> the panel above dead-leaf level. Instead, we install large Lithium
>> primary cells which give well over a year's operation.
>> 
>> Stephen
>> 
>> On Sun, 7 Jan, 2018 at 7:02 AM, Mark Atherton
>> wrote:
>> > Just been digging through Youtube and found some random but
>> > interesting projects/tutorials.
>> >
>> > Will post each as a separate subject.
>> >
>> > LoraWAN: Extremely long range, low power wireless communication
>> > https://www.youtube.com/watch?v=7n8t62anxIQ
>> >
>> > also 
>> https://www.youtube.com/channel/UCu7_D0o48KbfhpEohoP7YSQ/videos
>> >
>> > HNY, Mark
>> >
>> >
>> >
>> > _______________________________________________
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