Looks I succeed. I had to change the LOW fuses to correct value. I modified the APM Optiboot bootloader to accept 4MHz external oscilator. Here is the correct settings which need to be add to the boards.txt file:

##############################################################

apm96_4MHz.name=APM Optiboot external 4MHz noBOD 38400baud

apm96_4MHz.upload.tool=avrdude
apm96_4MHz.upload.protocol=arduino
apm96_4MHz.upload.maximum_size=32256
apm96_4MHz.upload.speed=38400
apm96_4MHz.bootloader.tool=avrdude
apm96_4MHz.bootloader.low_fuses=0xfd
apm96_4MHz.bootloader.high_fuses=0xde
apm96_4MHz.bootloader.extended_fuses=0x07
apm96_4MHz.bootloader.path=optiboot_v50
apm96_4MHz.bootloader.file=atmega328_1a_4MHz.hex
apm96_4MHz.bootloader.unlock_bits=0x3F
apm96_4MHz.bootloader.lock_bits=0x2F
apm96_4MHz.build.mcu=atmega328p
apm96_4MHz.build.f_cpu=4000000L
apm96_4MHz.build.core=arduino
apm96_4MHz.build.variant=standard

##############################################################

I had to change following lines:
apm96_4MHz.upload.speed=38400
apm96_4MHz.bootloader.low_fuses=0xfd
apm96_4MHz.build.f_cpu=4000000L

I also changed the file name to: apm96_4MHz.bootloader.file=atmega328_1a_4MHz.hex but the file is exactely the same as the original one. I also changed the name in the beginning of each line.

Currently looks it is working well. I will add more info later if all runs ok after some testing.

And here is also nice FUSES configurator.

@gohan - you are right. There is not much sense to have the gateway on the garden. To explain it a bit more. I wanted to create a device which would mix a LPWAN with NRF24. I already have some code for it which do not use mysensors at all. It is still work in progress but it collect data from couple of NRF24 and every 15 minutes it send the data via LPWAN Sigfox module to backend. I was thinking to implement similar solution with mysensors libaries. I understand that it does not give much sense to do so (especially in case that Sigfox LPWAN is very limited by transmited data and lets say no download link at all), but I would like to give it a try. I also need to say that I am new in mysensors and I did first testing of it just today

Another thing is that if I would be able to access some wifi network on the garden I would use ESP8266 as gateway with NRF24 if possible. Then I can imagine that it would give sense to have such device which would have power down mode enabled for most of the time which I can see like a good solution for smaller systems.

But like I said, I am new in mysensors project so maybe I do not have enough overview about it yet, then sorry for asking stupid questions here.

@gohan - I am trying to build a solution for more scenarious. For a small garden with just couple of sensors I can imagine that the LPWAN with NRF24 will be good enough. Then for bigger gardens would be better to use long range radious or some other soulutions. In my case I am about 500m from the garden. There are buildings and trees between my home and garden. I wanted to use some cheap solution. So I wanted to make it with NRF24. I tested the long range NRF24 but it was not reliable for this distance with buildings and trees between. But like I said I would like to make a project where more solutions will be available to fit more scenarious to let people re-use it.

@mfalkvidd and @hek - ok, thanks for this info I did not know that as I am new in mysensors. Good to know that it is already implemented in mysensors.
Thanks.

@wikibear - no problem

Hi all,
I am sory for this stupid question but I still do not understand correctly the MQTT. Currently I build my first mysensors network with SerialGateway connected to RPi with Domoticz and it is working ok. I was just wondering what is the MQTT gateway good for and what are the differences and advantages when compared with SerialGateway. Does MQTT gateway affect only the communication between Controller (RPi with Domoticz) and MQTT gateway or it also have impact on the Gateway and nodes communication? Is the whole system more stable with MQTT or what is it good for in comparison with serial gateway.

Thanks in advance for your explanation.

Looks I succeed. I had to change the LOW fuses to correct value. I modified the APM Optiboot bootloader to accept 4MHz external oscilator. Here is the correct settings which need to be add to the boards.txt file:

##############################################################

apm96_4MHz.name=APM Optiboot external 4MHz noBOD 38400baud

apm96_4MHz.upload.tool=avrdude
apm96_4MHz.upload.protocol=arduino
apm96_4MHz.upload.maximum_size=32256
apm96_4MHz.upload.speed=38400
apm96_4MHz.bootloader.tool=avrdude
apm96_4MHz.bootloader.low_fuses=0xfd
apm96_4MHz.bootloader.high_fuses=0xde
apm96_4MHz.bootloader.extended_fuses=0x07
apm96_4MHz.bootloader.path=optiboot_v50
apm96_4MHz.bootloader.file=atmega328_1a_4MHz.hex
apm96_4MHz.bootloader.unlock_bits=0x3F
apm96_4MHz.bootloader.lock_bits=0x2F
apm96_4MHz.build.mcu=atmega328p
apm96_4MHz.build.f_cpu=4000000L
apm96_4MHz.build.core=arduino
apm96_4MHz.build.variant=standard

##############################################################

I had to change following lines:
apm96_4MHz.upload.speed=38400
apm96_4MHz.bootloader.low_fuses=0xfd
apm96_4MHz.build.f_cpu=4000000L

I also changed the file name to: apm96_4MHz.bootloader.file=atmega328_1a_4MHz.hex but the file is exactely the same as the original one. I also changed the name in the beginning of each line.

Currently looks it is working well. I will add more info later if all runs ok after some testing.

And here is also nice FUSES configurator.

Actually the capacitance of the battery is not a problem for now. The time of wake up intervals and listen period can be changed. What I need to solve is the 4MHz bootloader.

Yes, I need the serial communication also during the operation of the chip. That is the reason why I want to switch to 4MHz. The node is in sleep mode for 8 seconds. Then it wake up for 500ms to listen if any communication is received on NRF24L01+. Then also every 15 minutes, the node is transfering received data from NRF24 to Sigfox backend (6 sensors values in one message) via LoRa module. Currently I tested 11 days running on 1MHz without problem. The voltage drop after this 11 days is about 0,3V. So on 2AA NiMH bateries it should last for about 1 month without bateries charging. There is required serial communication between ATMEGA328P and Sigfox. That is the reason for 4MHz.

You are right it looks like a good solution for such project. But I wanted to keep the project running on AA NiMH bateries as for me it is safe way let's say As I do not have any experiences with LiFePO4 and also no charger for them. But I should start focus also on such power supply in the future. Anyway, like you said it is a bit different topic but thanks anyway for your reply.

For me it looks like the best solution when I want to run the node for 2AA batteries without power regulator. As the spec of ATMEGA328P is that with 4MHz it can run from 1.8V. Which is exactely 2AA NiMH bateries at the end of the capacity. Then I also do not want to use 1MHz internal oscilator as it makes sometimes troubles when serial communication is used. So that is the reason for 4MHz node.

Hi all,
I would like to ask you about 4MHz bootloaders for ATMEGA328P. I make a project where I want to use ATMEGA328P running on 4MHz with external oscilator. Is there any possibility how to convert bootloaders to 4MHz? Or are there any already created? Currently I was using mostly APM Optiboot internal 1MHz noBOD 9600 BAUD bootloader. Would be there possibility to convert it to 4MHz external?

Here is info about the APM Optiboot bootloader if needed.

But anyway, it can be any other bootloader which would be converted to 4MHz.

Thanks.

Hi all,
I am sory for this stupid question but I still do not understand correctly the MQTT. Currently I build my first mysensors network with SerialGateway connected to RPi with Domoticz and it is working ok. I was just wondering what is the MQTT gateway good for and what are the differences and advantages when compared with SerialGateway. Does MQTT gateway affect only the communication between Controller (RPi with Domoticz) and MQTT gateway or it also have impact on the Gateway and nodes communication? Is the whole system more stable with MQTT or what is it good for in comparison with serial gateway.

Thanks in advance for your explanation.

@wikibear - no problem

@neverdie - by the way. Would be there some easy solution for RFM95 as a gateway? I mean following. There would be gateway or maybe better to say forwarder which would take data from NRF24 and will resend them via RFM95 to another RFM95 which would be connected to the gateway. Is there some direct way in mysensors? If not what about to have 2 nodes which would be connected via serial communication (RX and TX pins). One node would have NRF24 and second one would have RFM95. Node with NRF24 would be set as serial gateway. Then node with RFM95 would be only a simple sketch where serial communication received will be send via RFM95 as P2P communication to the gateway with RFM95 which will be then connected to internet via Wiznet 5100 for example.

Reason why I would like to have it is the fact that the garden is without the external power source and I need to reduce it as much as possible. Then it is also far for the NRF24 to reach directly the gateway. I also want to reduce the cost of the network so I want to use mostly NRF24 as cheaper alternative.

Ok, great. Thanks.