HL7618RD part successfully negotiates PPP via UART, RC6711 part does not

We have product prototypes using the HL7618RD part in cell module that is carrier certified by Nimbelink. That module is no longer available so we’re attempting to replace it with another Nimbelink product using the RC6711 part.

This is a microcontroller-based application using a 3rd party RTOS, IP stack, and PPP driver. Comm is via UART, carrier is Verizon. The APN for context 3 is “we01.vzwstatic” which connects with a static IP address. This boot-time log shows the AT-sequence and some application trace messages:

17:35:11:414 Start network interface
17:35:11.418 cellStartPPP
17:36:11.467 TX: AT
17:36:11.477 RX: OK
17:36:11.479 Power is UP.
17:36:12.127 TX: AT+CGREG?
17:36:12.138 RX: +CGREG: 0,1
17:36:12.139 RX: OK
17:36:12.342 TX: AT+CGACT?
17:36:12.353 RX: +CGACT: 1,1
17:36:12.354 RX: +CGACT: 2,0
17:36:12.356 RX: +CGACT: 3,1
17:36:12.357 RX: +CGACT: 4,0
17:36:12.358 RX: +CGACT: 5,0
17:36:12.359 RX: +CGACT: 6,0
17:36:12.361 RX: OK
17:36:12.562 TX: AT+CGACT=1,3
17:36:12.573 RX: OK
17:37:18.001 Start PPP session
17:37:18.205 TX: ATD99**3#
17:37:18.238 RX: CONNECT 150000000

  • Removed LCP protocol messaging

17:37:22.339 PPP link up
17:37:23.267 Connection established.
17:37:23.268 Local address:

At this point the HL7618RD part was up and running. At this point the RC6711 part answers to “ping” - Handled by the modem, not my IP stack. A logic analyzer shows no activity on the UART output after the last LCP packet. RTS/CTS are both asserted.

Any ideas why there’s no comm?

then is the PPP connection OK?
Can RC7611 access internet?

The PPP connection isn’t OK with the RC7611, even though the “PPP link up” and “Local address:” messages are issued only after the PPP stack indicates successful PPP initialization.

Since the HL7618RD does access the internet, I’m thinking the RC7611 should be able to access as well since it uses the identical application and PPP stack code.

There is no activity on the UART receive data line after the LCP negotiation:

  • Some missing AT-setup function???
  • The RC7611 attempting to use USB comm instead of UART comm???

Then is it ok to use ppp on usb?

Can’t use USB. The app runs on a microcontroller with one USB port that’s used for local PC connectivity. Comm must be via UART, as it was with the HL7618.

then can you route out the USB of RC76 module and connect to linux PC for PPP dial up?
BTW, are those +KTCP /+KUDP/+KHTTP protocol commands working fine?

This is not in a linux environment. Unless I"m badly mistaken, I believe +KTCP /+KUDP/+KHTTP are commands used with “socket dials” not PPP.

Didn’t you want to know if PPP dial up is working fine in USB?

i have no further idea to get more clue if those two tests are not under consideration.
good luck!