I want to use the RAK3172 for an industrial sensor as AT-Modem (using “AT+VER=RUI_4.2.0_…”). The 3172 is set to “LPM=1” and “LPMLVL=2” for lowest power ( < 2uA).
Most times communication works fine, but sometimes it seems, the 3172 does not understand the first sent byte (in Echo-Mode it replies an invalid character instead of the first ‘A’ and the reply is “AT_COMMAND_NOT_FOUND\r\n”).
I checked it very carfully (Host sets light Pullups and 115200 Baud timing is precise).
Question: Is this a known topic? How can I solve it? I want to keep the 115200 Baud.
Of course, I could repeat the command several times if the answer is “AT_COMMAND_NOT_FOUND\r\n”, but maybe there is a better solution?
I experienced this before but during times when the module is busy for example trying to join the network. It will still be best to validate replies to the command you send so you can resend if it fails. Also, you can give gaps on sending each command sent.
Hello Carl,
for me it seems the RAK3172 has a problem with the MSBs for the first received Byte. Maybe its internal timing of the Low-Power UART has a deviation (at room temperature)? It seems the following sent bytes are correctly recognised.
E.g. if sent 0x41 (‘A’) this is sometimes detected as 0xC1 or 0x81, as shown below.
I’ll continue the tests. Maybe to ignore “out of range” characters could be a solution for your next firmware, so bytes like 0x00, etc… could wake the 3172 safely?
But can you share me where Channel 2 and Channel 4 of the probes are connected? Channel 4 appears to send the command. But I am not sure where Channel 2 is connected.
I use the bare RAK3172-E/-SIP with latest Firmware 4.2.0 as simple AT-Terminal. CH4 is connected to UART2_RX, CH2 to UART2_TX. Modul is supplied with 3.3V and nothing else connected. This is my setup:
AT+BAND=4 // 4:868 MHz
AT+NJM=1 // 1: OTAA
AT+RETY=0 // Ni RX-Best. Wdh
AT+CFM=1 // Confirm TX lassen
AT+LPMLVL=2 // LowPower USART
AT+LPM=1 // LowPower act.
AT+ADR=1 // !!!Automatic Data Reduction, not for moving Devices!!!
Just as an info: another module we use, answers with “WAKE” when its UART is ready. After this the UART is on for a certain time.
Hope to find stable solution soon.
Thanks for your support!
Jo
PS: I added repetitions for each sent command. However, even this often fails.
So I think it would be very important to have a solution.
Errors in RED “(Command Not Found”), Rest worked. Timeline:
Hello Carl,
it is a simple test.
I send “AT+SEND=1:xxxx\r”, where xxxx is a Hex counter.
The command is sent every 120 seconds with ADR enabled and Gatway 10 mtrs away (Chirpstack sets DR to 5). We are using already LTE-M / -NB on the hardware from the customer (environment technology), now LoRa should be added.
Thanks for your support!
Jo
