IoT LoRa pHAT node - Intermittent Serial communication problems.

[peach-e]

I'm trying to follow the LoRA Node tutorial for Raspberry Pi here:
https://learn.pi-supply.com/make/getting-started-with-the-raspberry-pi-lora-node-phat

I'm getting stuck during the hello world script due to the serial interface timing out. But not all the time. Sometimes it times out waiting for a response from a gateway (I don't have my own) and once or twice I got a handshake to appear on the TTN console.

Using

• Raspberry Pi Zero W
• Raspbian Buster Lite
• IoT LoRa pHAT node
• rak811 version 0.8.1
• Tutorial here: https://learn.pi-supply.com/make/getting-started-with-the-raspberry-pi-lora-node-phat

Steps to Reproduce

1. Install the pHAT node onto the Pi as per tutorial.
2. Enable serial but disable serial console, and set dtoverlay=pi3-miniuart-bt in /boot/config.txt as per tutorial.
3. Install RAK811 library as per tutorial.
4. Get Device EUI with commands:

   $ rak811 -vd hard-reset
   DEBUG:rak811.serial:Serial initialized
   Hard reset complete
   
   $ rak811 -vd get-config dev_eui
   DEBUG:rak811.serial:Serial initialized
   DEBUG:rak811.serial:Sending: >at+get_config=dev_eui\r\n<
   DEBUG:rak811.serial:Received: >OK34************14<
   34************14
   

5. Create an Application on the V2 console for The Things Network.
   • Application ID & Description: Set
   • Handler: ttn-handler-eu (Automatically selected)
   • Application EUI: (Automatically chosen on v2 console.)
   • 1 Device:
     • Application ID: (Matches high-level application ID)
     • Device ID: (I typed something in)
     • Activation Method: OTAA
     • Device EUI: (Use my device EUI)
     • Application EUI: (Matches high-level application EUI)
     • App Key: (Auto Generated)
   • NOTES on V3 Console:
     • When adding device, use
       • OTAA
       • Specify LoRaWAN version MAC V1.0.2
       • Server nam1.cloud.thethings.network
       • Regional Parameters version PHY V1.0.2 REV B.
     • AppEUI is not automatically provided anymore. You make something up or make it match your old v2 app EUI.
     • Frequency Plan: US915 FSB 2
     • Regional Parameters Rev B
     • LoRaWAN Class Capabilities: Leave all unchecked.
       • However, I think I saw Rak811 Datasheet state that it supports Class C.
     • AppKey: Randomly generated
     • (All this stuff I got from the Migration Tutorial (https://www.thethingsnetwork.org/docs/the-things-stack/migrate-to-v3/migrate-using-console/)
6. Create the lora_node.py script as per tutorial.
   • Notes:
     • from rak811 import Mode, Rak811 doesn't work any more. Now, you have to use from rak811.rak811 import Mode, Rak811.
     • Dev EUI, App Key, App EUI set according to how the TTN app configured.
     • Band: US915 (Because I live in Canada)
     • Additional channel masks set as per tutorial for US915, inserted between the lora.set_config(dev_eui, app_eui, app_key) and lora.join_otaa() commands.
     • Run chmod +x on the script.
7. Run the script.

Expected Behavior

It either works, or maybe I'll get errors about talking to a gateway because I live a long ways away from one. (I bought the device for P2P communication primarily)

Observed Behavior

I get "Timeout while waiting for data" on the lora.join_otaa() step.

$ ./lora_node.py
Traceback (most recent call last):
  File "./lora_node.py", line 18, in <module>
    lora.join_otaa()
  File "/usr/local/lib/python3.7/dist-packages/rak811/rak811.py", line 411, in join_otaa
    self._send_command('join=otaa')
  File "/usr/local/lib/python3.7/dist-packages/rak811/rak811.py", line 237, in _send_command
    response = self._serial.receive()
  File "/usr/local/lib/python3.7/dist-packages/rak811/serial.py", line 156, in receive
    raise Rak811TimeoutError('Timeout while waiting for data')
rak811.serial.Rak811TimeoutError: Timeout while waiting for data

Run the script again. This time I get a similar timeout error on lora.mode = Mode.LoRaWan.

Okay, so I've got serial problems. But why did the first couple of commands go through? Let's try them again.

$ rak811 -vd get-config dev_eui
DEBUG:rak811.serial:Serial initialized
DEBUG:rak811.serial:Sending: >at+get_config=dev_eui\r\n<
RAK811 timeout: Timeout while waiting for data

Any ideas?

[peach-e]

I modified my lora_node.py script to print out the AT commands sent into the modem and the responses.

Script

#!/usr/bin/env python3
import logging
import sys

root = logging.getLogger()
root.setLevel(logging.DEBUG)

handler = logging.StreamHandler(sys.stdout)
handler.setLevel(logging.DEBUG)
formatter = logging.Formatter('%(asctime)s - %(name)s - %(levelname)s - %(message)s')
handler.setFormatter(formatter)
root.addHandler(handler)


from rak811.rak811 import Mode, Rak811

lora = Rak811()
lora.hard_reset()
lora.mode = Mode.LoRaWan
lora.band = 'US915'
lora.set_config(dev_eui='34*********************14',
app_eui='70*********************06',
app_key='E8***************************14')

lora.set_config(ch_mask = '0,FF00')
lora.set_config(ch_mask = '1,0000')
lora.set_config(ch_mask = '2,0000')
lora.set_config(ch_mask = '3,0000')
lora.set_config(ch_mask = '4,0000')

lora.join_otaa()
lora.dr = 5
lora.send('Hello world')
lora.close()

Result

$ sudo ./lora_node.py
2021-06-09 12:29:07,355 - rak811.serial - DEBUG - Serial initialized
2021-06-09 12:29:09,377 - rak811.serial - DEBUG - Sending: >at+mode=0\r\n<
2021-06-09 12:29:10,597 - rak811.serial - DEBUG - Ignoring untagged: ><
2021-06-09 12:29:10,715 - rak811.serial - DEBUG - Ignoring untagged: >Selected LoraWAN 1.0.2 Region: US915 <
2021-06-09 12:29:10,820 - rak811.serial - DEBUG - Ignoring untagged: ><
2021-06-09 12:29:10,925 - rak811.serial - DEBUG - Received: >OK<
2021-06-09 12:29:11,029 - rak811.serial - DEBUG - Sending: >at+band=US915\r\n<
2021-06-09 12:29:11,038 - rak811.serial - DEBUG - Received: >OK<
2021-06-09 12:29:11,143 - rak811.serial - DEBUG - Sending: >at+set_config=dev_eui:34**********14&app_eui:70*********06&app_key:E8*********************14\r\n<
2021-06-09 12:29:12,366 - rak811.serial - DEBUG - Received: >OK<
2021-06-09 12:29:12,471 - rak811.serial - DEBUG - Sending: >at+set_config=ch_mask:0,FF00\r\n<
2021-06-09 12:29:13,686 - rak811.serial - DEBUG - Received: >OK<
2021-06-09 12:29:13,790 - rak811.serial - DEBUG - Sending: >at+set_config=ch_mask:1,0000\r\n<
2021-06-09 12:29:15,005 - rak811.serial - DEBUG - Received: >OK<
2021-06-09 12:29:15,109 - rak811.serial - DEBUG - Sending: >at+set_config=ch_mask:2,0000\r\n<
2021-06-09 12:29:16,324 - rak811.serial - DEBUG - Received: >OK<
2021-06-09 12:29:16,429 - rak811.serial - DEBUG - Sending: >at+set_config=ch_mask:3,0000\r\n<
2021-06-09 12:29:17,644 - rak811.serial - DEBUG - Received: >OK<
2021-06-09 12:29:17,748 - rak811.serial - DEBUG - Sending: >at+set_config=ch_mask:4,0000\r\n<
2021-06-09 12:29:18,963 - rak811.serial - DEBUG - Received: >OK<
2021-06-09 12:29:19,068 - rak811.serial - DEBUG - Sending: >at+join=otaa\r\n<
Traceback (most recent call last):
  File "./lora_node.py", line 31, in <module>
    lora.join_otaa()
  File "/usr/local/lib/python3.7/dist-packages/rak811/rak811.py", line 411, in join_otaa
    self._send_command('join=otaa')
  File "/usr/local/lib/python3.7/dist-packages/rak811/rak811.py", line 237, in _send_command
    response = self._serial.receive()
  File "/usr/local/lib/python3.7/dist-packages/rak811/serial.py", line 157, in receive
    raise Rak811TimeoutError('Timeout while waiting for data')
rak811.serial.Rak811TimeoutError: Timeout while waiting for data

So it looks like that at+join=otaa command is gumming up the modem. Not even $ rak811 -vd reset lora will fix it; I actually have to power-cycle my Pi to get back to square 1.

Looking at the AT command reference here: https://downloads.rakwireless.com/LoRa/RAK811/Application_Notes/RAK811_AT_Command_Manual_V1.0.pdf

It looks like at+join does not accept any arguments. I'd investigate farther, but I'm having a heck of a time probing the serial port directly.

Question

Can someone please tell me a command that will let me talk to the modem with AT commands? I've been trying

$ picocom -b 115200 -d 8 -y n -p 1 /dev/serial0

But nothing appears in the console when I type things.

[peach-e]

All right. The correct serial command is

$ picocom --baud 115200 --echo --omap crcrlf /dev/serial0

And now I can run AT commands manually.

at+reset=0
OK
Welcome to RAK811

Selected LoraWAN 1.0.2 Region: US915 

at+mode=0

Selected LoraWAN 1.0.2 Region: US915 

OK
at+version
OK2.0.3.0
at+set_config=dev_eui:34*******14
OK
at+set_config=app_eui:70*********06
OK
at+set_config=app_key:E8*****************14
OK
at+join=otaa

It looks like I'm using the old version of the firmware, for which at+join=otaa is in fact a reasonable command (https://github.com/AmedeeBulle/pyrak811/blob/main/DOCS/RAK811%C2%A0LoRa%C2%A0AT%C2%A0Command%C2%A0V1.5.pdf).

But the command never returns it the modem doesn't get a lock on a gateway, so it just sits there without responding until I cycle the power. No wonder the serial interface was timing out.

Would upgrading the firmware help with this? I thought someone would have a gateway near here; the LoRa promotional material advertised a 10km radius and I'm in a populated area.