SABM and SABME swapped in frame.py

[vk2tds]

In the file frame.py, SABM and SABME classes have their modifiers swapped. The correct values should be :-

Class AX25SetAsyncBalancedModeExtendedFrame should have a modifier of MODIFIER = 0b01101111
Class AX25SetAsyncBalancedModeFrame should have a modifier of MODIFIER = 0b00101111

It also appears that the P/F flag needs more investigation, and should possibly be set. The basis for this is that my PicoPacket TNC with 1996 firmware has the P/F bit set. In my case, the picopacket is using 0x3f as the value for SABM.

I suspect that existing code uses a mask to ignore the p/f bit.

Following your code, you could ADD these MODIFIER = 0b01101111 and MODIFIER = 0b00101111 respectively for SABME and SABM.

[sjlongland]

So, I had a look… indeed, the AX25BaseUnnumberedFrame class defaults to PF=False, but we can override this in sub-classes.

However, the constructor for AX25BaseUnnumberedFrame was omitting passing pf to the superclass. Thus every U frame generated had PF=False regardless. Oops. :-)

I've now corrected this in the branch. Many thanks for spotting these omissions. There might be other U-frames where PF should be set True instead of the current default… we'll play those by ear I guess. :-)