Linux USB with HL6/8 development kit.

I have a HL6 and HL8 development kit. The demo board came populated with a HL6528. Unfortunately we want to use the HL8548 and have SIM cards for that network. We are removing the HL6528 and replacing with an HL8548 module. I was able to connect via the serial port of the HL6528. The Linux kernel created an FTDI driver/interface with USB connected and a ‘ttyUSB0’ was created. However, whenever I connected to this serial port, I was unable to get any communication to work.

The AT command manual has a large table at the end to say whether commands are supported. However, it only have info for the HL6528; the HL8548 is blank. There appears to be lots of documentation, but I don’t know what is relevant. Is ‘HiLo’ mean any HL device? We are evaluating replacing a Telit HSDPA module with the HL8548. I was burned several times with the Telit documentation, reading about the wrong module. Is there some sort of Rosetta stone on what the product line-up is for Sierra wireless and what documents are relevant?

The main thing I need to evaluate is ‘CMUX’ versus ‘USB’. It seems that the HL8548 will create either six CDC-ACM channels or three serial + three network. This seems great. I don’t like the CMUX protocol. Even though it is a standard, each and every vendor seems to have quirks. I need to support both modules and think that USB is probably better. I don’t know why it is reporting an FTDI device; maybe the USB gadget code is from FDTI? But I thought this was a special gadget; I have only used FDTI with a ‘Game Boy Advanced’ previously and not a GSM modem. Do I have the wrong port setup and/or need some other jumpers? Is there some manual/appnote I missed on using USB with a sierra product that is relevant to the HL8548?

The ‘FDTI’ connection is for the NMEA port. On the correct USB port, Linux lists the ID ‘1519:0020’; proper configuration is required to recognize the device.