Master-Slave like modbus on E220 lib

[Ivan]

I´m newbee with this module but I intend to implement a Master-Slave protocol using E220 lib, something like modbus but I don´t know if it´s possible.
Thanks everybody.

[Renzo Mischianti]

Hi Ivan,
I think you can use the fixed transmission like in the examples in this article.

Ebyte LoRa E220 device for Arduino, esp32 or esp8266: fixed transmission, broadcast, monitor, and RSSI – 4

If you give our some details we can try to be more specific.

And if you are Italian remember that the articles are also in Italian.

Bye Renzo

[Ivan]

Ciao Renzo,

Sono di origine italiana, più precisamente di Genova, ma sono nata in Brasile.

I´ll see the article but will give more details:

a) I thought the broadcast mode was just sending from the master to all (or some) slaves. I need two-way communication between master and slaves, with master asking the slaves if there is anything to send in a pooling.

b) If a slave has data to send, it sends and ends with ack/nack. And master pooling proceeds with the next slave.

Basically that’s it, it’s not hard to make a physical RS-485 network but doing it on lora, I’m a little lost.

Thanks for your patience

Ivan Assaritti

[Renzo Mischianti]

Hi Ivan,
do you know what kind of data (and the quantity) you must manage?

LoRa has the possibility to send a structured packet or a simple string, so as needed we can create a reliable and efficient transmission protocol, better than modbus which is widely used but has physical limitations.

Bye Renzo

[Ivan]

Hi Renzo.

Our application with more details:

1. Neither the master nor the slaves sleep as they will be powered all the time by the eletricity network

2. Each time a slave has something to send to the master, the set of information does not exceed 8 bytes, but it can be divided into more than one transmission, if necessary, without problem.

3. As soon as the master receives data from a slave, it stops pooling and will process the slave’s operation, only resuming pooling after this processing, which can take up to 1 minute or more.

4. For security reasons, it is mandatory to have CRC and encryption in each communication.

5. The network will always be formed by a master and up to 8 slaves, typically from 2 to 5.

6. We already tried to use an arduino with an RFM95W radio and the lora.h library, changing the LoRaDuplex example but we lost a lot of packages, so we are going to the E220.

I believe is this.

Thanks

Ivan

[Renzo Mischianti]

Hi Ivan,
now we have sufficient information.
First of all here I add a table comparison of EByte devices

                       E32                       E22                       E220
Chip                   sx1276-sx1278             sx1262-sx1268             LLCC68
Range                  3Km - 8Km                 5km - 11km                5Km - 10Km
Repeater               No repeater               Repeater                  No repeater
Remote conf            No                        Yes                       No

Power consumption      Best                      Good                      Very Good
                       Sleep 4μA                 Sleep 496μA               Sleep 6μA
Transmission and receiving have similar power consumption.

Message size bytes     58                        240                       200
Buffer size bytes      512 (ok)                  1000 (good)               400

Max air data rate (bps) 19.2k                    62.5k                     62.5k

Encryption             One standard              Configurable              Configurable crypt
Price                  Less expensive            More expensive            Less expensive

1. Neither the master nor the slaves sleep as they will be powered all the time by the eletricity network

If you want we can add after the WOR.

2. Each time a slave has something to send to the master, the set of information does not exceed 8 bytes, but it can be divided into more than one transmission, if necessary, without a problem.

If you select e22 or e220 the packet size is sufficient to send all the data.

3. As soon as the master receives data from a slave, it stops pooling and will process the slave’s operation, only resuming pooling after this processing, which can take up to 1 minute or more.

For this problem, we can adopt various solutions.

• The master tells the various clients when it is available for reception, and polls all clients in rotation.
• IF the sending frequency is quite low the buffer of the device It’s sufficient.
  If you select an e220 you have available 400bytes of buffer and if you set the packet size at 32bytes the LoRa device can store 12 packet without the intervention of the microcontroller.
  An e22 can store about 31 packet of data in his buffer (1000bytes).
• If you have a high sending frequency you can build a gateway with a microcontroller and put all the packets to a push server and another (or more than one) microcontroller to process the packet.

4. For security reasons, it is mandatory to have CRC and encryption in each communication.

E22 and E220 have configurable and transparent encryption.
You can develop CRC but remember these devices monitor the ambient noise and with a reduction of air data rate, It’s improbably that they lost packet.

5. The network will always be formed by a master and up to 8 slaves, typically from 2 to 5.

These devices support hundreds of devices.

Tell me if these informations are sufficient.
Bye Renzo

[Ivan]

Hi Renzo,

I believe with your information we can produce an introductory code and test it here.

If the code works, I’ll share it here for everyone’s knowledge.

If it doesn’t work and we can’t figure out why, I’ll call you again 🙂

Thank you very much for your attention!

Ho visto che sei di Perugia.
È una bellissima regione per la sua natura e la sua storia.
Congratulazioni!

Ivan

[Author]

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