HL78xx PPP port best speed setting

IoT Modules HL78
1

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?

2

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

3

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?

4

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

5

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

6

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.

7

thanks for the awesome information.

8

thanks my issue has been fixed.