Latest stable version 1.5, random TXDelay timing problem #170
Description
I have Direwolf 1.5 installed on a Raspberry Pi3 ( with freshly installed Raspian Stretch). The setup uses linBPQ and Direwolf KISS mode 127.0.0.1:8001. I am able to make connections with no problem on 1200 and 300 baud, but I notice random delays between the PTT activation and actual transmitted audio. I have TXDelay set at 30ms, but I'm seeing delays up to 2 seconds (maybe even more at times) between PTT keydown and transmitted audio. Seems purely random; I would say 50% of the transmissions have this large delay, and the rest are normal. The long delays themselves are random in length also, and occur on any transmit, whether an ack or a command sent to the other station. The Pi3's CPU is generally around only 3% use when I'm using packet; no spikes during the delays or anything. This same problem was in the 1.5-beta4 version as well.
PTT is activated by the Pi3's GPIO pin 26.
USB audio is the Syba SD-CM-UAUD.
Timings in bpq32.cfg are at the suggested settings in the Direwolf user guide.
The BPQ config file is very basic; no other timing settings other than the following:
PORT
PORTNUM=1 ; Port number
ID=VHF Packet 1200-baud ; PORTS command text
TYPE=ASYNC :RS232 connection
IPADDR=127.0.0.1 ; DIREWOLF
TCPPORT=8001 ; DIREWOLF
SPEED=19200
CHANNEL=A ; TNC channel
MAXFRAME=1 ;Max outstanding frames
FRACK=4000 ; Level 2 timeout (ms)
RESPTIME=40 ; Level 2 delayed ACK (ms)
RETRIES=10 ; Level 2 max retries
PACLEN=128 ; Max packet length (bytes)
TXDELAY=100 ; Transmit keyup delay (ms)
SLOTTIME=100 ; CMSA interval timer (ms)
TXTAIL=100
PERSIST=63 ; Persistence (256/(# transmissions-1)
DIGIFLAG=1 ; Allow Digipeat on this port
ENDPORT
Direwolf config settings that are enabled are:
ADEVICE plughw:1,0
ACHANNELS 1
MODEM 1200 1200:2200
PTT GPIO 26
KISSPORT 8001
I also tried different ARATE settings at 11025 and 48000, but no change was seen.
Output when I run it is:
Dire Wolf version 1.5 (Sep 22 2018) Beta Test 4
Includes optional support for: cm108-ptt
Reading config file direwolf.conf
Audio device for both receive and transmit: plughw:1,0 (channel 0)
Channel 0: 1200 baud, AFSK 1200 & 2200 Hz, E+, 44100 sample rate / 3.
Ready to accept AGW client application 0 on port 8000 ...
Ready to accept KISS TCP client application 0 on port 8001 ...
Attached to KISS TCP client application 0...
Ready to accept KISS TCP client application 1 on port 8001 ...
KISS protocol set TXDELAY = 10 (*10mS units = 100 mS), port 0
KISS protocol set Persistence = 63, port 0
KISS protocol set SlotTime = 10 (*10mS units = 100 mS), port 0
KISS protocol set TXtail = 10 (*10mS units = 100 mS), port 0
KISS protocol set FullDuplex = 0, port 0