Sierra MC7455 not communicating

Raspberry Pi Network HATs 3G/4G&LTE Base HAT
1

I’ve had to switch from QC to Sierra’s modem for the sixfab hat. I’m assuming ppp is the same but it is not communicating. At least the QC would connect and get an IP (Verizon just wouldn’t let us register it). This one won’t even get that far:

pi@raspberrypi:~$ sudo pon
pppd options in effect:
debug # (from /etc/ppp/peers/provider)
updetach # (from /etc/ppp/peers/provider)
dump # (from /etc/ppp/peers/provider)
noauth # (from /etc/ppp/peers/provider)
remotename 3gppp # (from /etc/ppp/peers/provider)
/dev/ttyAMA0 # (from /etc/ppp/peers/provider)
115200 # (from /etc/ppp/peers/provider)
lock # (from /etc/ppp/peers/provider)
connect chat -s -v -f /etc/chatscripts/chat-connect -T vzwinternet # (from /etc/ppp/peers/provider)
disconnect chat -s -v -f /etc/chatscripts/chat-disconnect # (from /etc/ppp/peers/provider)
nocrtscts # (from /etc/ppp/peers/provider)
modem # (from /etc/ppp/peers/provider)
asyncmap 0 # (from /etc/ppp/options)
lcp-echo-failure 4 # (from /etc/ppp/options)
lcp-echo-interval 30 # (from /etc/ppp/options)
hide-password # (from /etc/ppp/peers/provider)
novj # (from /etc/ppp/peers/provider)
novjccomp # (from /etc/ppp/peers/provider)
ipcp-accept-local # (from /etc/ppp/peers/provider)
ipcp-accept-remote # (from /etc/ppp/peers/provider)
ipparam 3gppp # (from /etc/ppp/peers/provider)
noipdefault # (from /etc/ppp/peers/provider)
ipcp-max-failure 30 # (from /etc/ppp/peers/provider)
defaultroute # (from /etc/ppp/peers/provider)
usepeerdns # (from /etc/ppp/peers/provider)
noccp # (from /etc/ppp/peers/provider)
noipx # (from /etc/ppp/options)
abort on (BUSY)
abort on (NO CARRIER)
abort on (NO DIALTONE)
abort on (ERROR)
abort on (NO ANSWER)
timeout set to 30 seconds
send (AT^M)
expect (OK)
alarm
Failed
Script chat -s -v -f /etc/chatscripts/chat-connect -T vzwinternet finished (pid 489), status = 0x3
Connect script failed

*** Any ideas?

2

Hi @gcrow,

UART connection with Base HAT: Link to FAQ
Please, make sure to communicate with the module via AT commands.

Thank you.

3

I have soldered the points like in the FAQ. It works for a EC module and when I replace it with the Sierra, the same pon does not work - it errors out like I noted above.

4

I’m running the default script of pon. Is there something else I should use?

5

Did you compare the module’s pinout with the pinout given on the documentation?

PIN 11 and PIN 13 of mini PCIe should be UART_RX and UART_TX respectively.
However, observing the sierra MC7455 mini PCIe module’s datasheet, we can say that these pin are not similar. Since the USB pin are similar you can use the USB for communication.

Please test with USB once. Connect the usb cable, change the /dev/ttyAMA0 to /dev/ttyUSB3 in /etc/ppp/peers/provider

6

Thanks ensar. I can’t use the USB per requirements for the product. It has to be uart. The reason we got the sierra wireless mc7455 is that sixfab said it was supported. Is there a different modem card that IS supported using uart?

7

So far except the Quectel modules, the UART pin on the mini PCIe of different vendors are at different pin location. Since the HAT is recommended to use via the USB by default, the compatibility module list is also listed for the USB.

8

Is there any other modem I can use like the QC model that has the same pinouts?