Send Size limit on GSM Data Flow?


The ADL User Guide for Open-AT v3.03 says that there is no limit to the size of data block that adl_fcmSendData can send on a GSM Data flow.

I sent a 590-byte block, adl_fcmSendData returned OK, but the data received by the other party was wrong:
The first 270 bytes were correct, but then the received data started again, repeating bytes already received!

Interestingly, the ADL User Guide does mention 270 bytes as the packet size when receiving on a GSM Data flow.

Is this a known feature?

Does this mean that blocks passed to adl_fcmSendData should be limited to 270 bytes?


I didn’t pursue this but, for an easy life, just limited my transmit blocks to under 270 bytes! :confused:

However, I’m now trying to implement a 1K-XMODEM upload, and the blocks are being received incorrectly.

I have a suspicion that this may be due to the same problem - so, just revisiting this, does anyone have any hints or tips…?

(I’ve had 1K-XMODEM downloads working for ages - it’s just the upload that’s new; ie, sending data from the modem).

Hardware: Fastrack M1306B (contains Q2406B);
Firmware: 6.57
OS: 3.12

(at the time of my original post, it would’ve been 6.51 and 3.03)


Yes, this definitely looks like the same bug:

The upload works fine with 128-byte XMODEM blocks;

Looking at the “good” data uploaded via 128-byte XMODEM, and the “bad” data received via 1K-XMODEM, I can see that the 1K-XMODEM data gets corrupted after about 270 bytes:angry: