CODEWITHSUNDEEP
serial-portputtyquectel
G. Communithings
G. Communithings

Reputation: 101

Putty carriage return corruption

I am trying to make a windows executable talk with a Quectel module through serial.

The tool always fails at the first step which is to read the module's firmware version with an AT command (AT+CGMR\r).

I tested to send the same command to the module, using Putty and typing out the command, and it worked like a charm.

However, when I type the command in a notepad (including the carriage return at the end), then copy the text and paste it into putty (my idea was to get closer to the behavior of the .exe by sending the command faster), 2 weird things happen:

1 - I don't get a response from the module until I send a second carriage return by pressing Ctrl-M in putty. I am certain that the character is copied into the clipboard from the notepad though... 2 - The module does not receive "AT+CGMR" but "AT+CGMM" (which is also a valid command). I tested other variations and concluded that the last text character is always replaced by the second to last text character. So AT+CDFR gives AT+CDFF. AT+PILJ gives AT+PILL etc... I am certain that is what the module receives because echo mode is on so the module prints out the command it received before the answer to said command.

To summarize:

By typing on the keyboard directly into putty I get:

AT+CGMR
SSB,V150R100C10B200SP1

SECURITY_A,V150R100C20B300SP5

PROTOCOL_A,V150R100C20B300SP5

APPLICATION_A,V150R100C20B300SP5

SECURITY_B,V150R100C20B300SP5

RADIO,Hi2115_RF0

OK

Which is the expected output. But by copying and pasting the exact same text from notepad I get:

AT+CGMM
BC95GJB-02-STD

OK

and that, only after I press Ctrl-M. Before that there is no answer at all so it is as if the module never received the carriage return.

I can't figure out what is going on here... Any help appreciated.

Upvotes: 0

Views: 540

Answers (1)

user16782446
user16782446

Reputation: 11

I worked a lot with Quectel 4G modules. Maybe make a simple data tracer.

Download dumb terminal Termite so you can see single hex characters including non printable. Connect termite to to read a stock USB to serial adaptor. Make sure the adaptor is set to 3.3V not 5V. The Quectels are 1.8V domain but can scrape in and drive 3.3V logic. I assume you are driving your Quectel with 1.8V.

Hardware wise attach the Rx pin of the Quectel module to the USB module Rx pin then you can see exactly the characters going into the Quectel from Notepad and Putty. (Sometimes you may need a 1K in series with the USB Rx pin to reduce loading). Bingo, you can see exactly the characters the Quectel is getting. I found many bugs doing this.

Upvotes: 1

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