HL78xx PPP port best speed setting

We’re using:

HL7800.4.4.14
HL78xx.4.4.14.0.RK_02_01_02_00_101.20200702
2020/07/02 23:50:39
IMEI-SV: 3546160908827509
Legato RTOS: 18.09.4.ALT1250.rc3 2020/03/02 10:50:25
atSwi: 30.00
UBOOT: 01.03
Apps: RKAPP_02_01_02_00_94__31f472b547df5417a8f942dd14d4c8cb9bf65395
MAC: ALT1250_02_01_02_00_91_FW
PHY: 12.50.233970
PMP: 234124
SBUB: 1
SBFW: 1
RPuK: 53F7A48A
FPuK: 139A8E70
RBUB: 0
RBFW: 0

and use PPPd to create a modem network interface as explained here:

NOTE: we can’t use the modem tcp/ip stack since we have a lot of applications using the linux tcp/ip socket interface.

When the connection is up, we experience a pretty “bad” IP throughput, isn’t this limited
by the speed=115200 bps as configured for the PPP data port (/dev/ttyACM0)?

As you know LTE-M supports max 1 Mbps UL/DL, how do we setup PPP (port) to reach this speed?

Have you increased the baud rate and see if there is improvement

how do I increase the (PPP) port baudrate?
setting it with “AT+IPR” doesn’t work and the AT+IPR? response has a problem, see:
at+ipr?

+IPR: -1733465512

OK

increasing the baud rate in the /etc/ppp/peers/hl78xx pppd call script also doesn’t work,
as the PPP port doesn’t respond.

how to increase the speed?

No idea why it is negative value, never see such thing before
You can try newer fw

at+ipr?

+IPR: 115200

OK
ati3

HL7800.4.6.8.0

OK

thanks for your answer, yes i’ll try that.

somehow I missed:
https://source.sierrawireless.com/-/media/support_downloads/airprime/application_notes_and_code_examples/airprime_hl78xx_establishing_a_ppp_session_with_a_linux_host_rev1_0.ashx

this answers most of my questions

what I also missed is that at+ipr is obviously only relevant for a the uart/serial port,
we’re using the USB mode (ttyACM0-2) and so the configured port speed (as shown by “stty -F /dev/ttyACM1”) isn’t relevant.

Tests with the new firmware (HL7800.4.6.9) show the IP throughput is a bit better, see:

~ # iperf3 -t 600 -p 5002 -c speedtest.serverius.net
Connecting to host speedtest.serverius.net, port 5002
[  5] local 10.235.60.191 port 35576 connected to 178.21.16.76 port 5002
[ ID] Interval           Transfer     Bitrate         Retr  Cwnd
[  5]   0.00-1.00   sec   101 KBytes   826 Kbits/sec    0   36.8 KBytes
...
[  5] 599.00-600.00 sec  0.00 Bytes  0.00 bits/sec    0   28.6 KBytes
- - - - - - - - - - - - - - - - - - - - - - - - -
[ ID] Interval           Transfer     Bitrate         Retr
[  5]   0.00-600.00 sec  18.8 MBytes   262 Kbits/sec  696             sender
[  5]   0.00-600.00 sec  18.6 MBytes   261 Kbits/sec                  receiver

iperf Done.

I guess this is acceptable.