There’s been some off topic discussion in a couple other threads about using Digi SX (Pro) radios instead of the Ardusimple LR (XLR) ones and I have some more info to add so I thought it best to start a new thread to document my venture in this direction. For background on the previous discussions see post 190 to 213 here and post 6 to 19 here.
Ardusimple builds an adapter board with SMA connector and solders the SX (20mW) or SX PRO (1W) radio for you and calls it LR and XLR respectively. The bare radio comes as a SMT, hence the adapter board, but you can get a version with a U.FL antenna connector and solder 2mm pins yourself for less money then buying from Ardusimple but keep in mind you then also need a u.fl pigtail and antenna (the antennae incl. from Ardusimple are good ones). According to @torriem Ardusimple’s LR/XLR come with Digi’s 9Xtend hopping firmware which I can also confirm and my new SX radios also came with the 9Xtend firmware already installed. You can use any XBee USB adapter to program the bare SX radios yourself or if you have one of the simpleRTK2B boards then use it’s XBee header and XBee USB port (thanks @Mechanic)
Digikey list of SX family radios
Pin soldering & pinout comparison
Solder a 2mm pin header (10 pin piece) to the SX radio on the left side from pin #2-11 (skip pin 1) and another 10 pin header to the right side pin #24-33 (aligned with the first header). As you can see from the diagram, the pinout then matches. For a base radio, you only need the connections in yellow once the radio has been programmed.
This is how I setup my pin headers, so that the pins didn’t stick out past the pcb, this way I could make sure the pcb pad soldered. I used my XBee USB adapter to hold things in place but as mentioned by @Mechanic you can use your arduSimple RTK2B type board too for holding and programming later.
Using some solder flux helps to help with soldering and prevent bridging, you’ll see in some pics it wanted to bridge to the rf shield.
I tried hard to make sure the pins soldered properly to the pads, I quickly noticed some did not so in the end I always tested their adhesion by gently pulling on each pin with a tool. On one I pushed the pin header’s plastic down to get better access to the pins, on the other I left it in place.
I have now ordered an XBee SMT to THT adapter from JLCPCB.
The design is here, currently it’s untested.
It costs me about half for the SX PRO incl. a u.Fl pigtail and 900mhz antenna compared to arduSimple’s XLR kit and about 1/3 for the SX (LR kit)
Here’s an update with the on board sma connector option.
Use Digi’s XCTU for configuring. Following the link to the xctu user guide for downloads and help. I used the Profile → Create Configuration Profile option to backup/save the arduSimple config but after studying the settigns for a while I realized they are using a mostly default config, only changing the following items. Make sure to write each change to the radio as you go along, for some reason I had trouble writing all changes at the end.
- CM 5555555555555555555555555
For NA, yours might be diff
- ID xxxx
Make this the same for all the radios that you want to communicate, base and rovers are the same
- MT 0
I set my broadcast re-transmits to 0, because if you’re sending data every second like most do for RTCM then you’ll soon have another new packet going out, no need to keep sending the old one, plus this lowers the required RF data rate (see next).
- BR 0
I’m going to try the lowest possible RF rate in hopes that it’s sufficient because that increases the receiver sensitivity substantially which should increase the range. (to be tested)
- PL 0 for rover, 2 for base
There is application to have your rover send data back but with multiple rovers that quickly becomes useless so I set mine to the lowest setting, but set your base to the highest for max range.
- DL 0 for rover, FFFF for base
FFFF is the broadcast address for your base to send to all rovers, and I used 0 for the rovers so that if any rover does try to send data all other radios will ignore it.
- TO 40
On my arduSimple LR kit and on my new SX radios, this was set to 40 but on my new SX PRO this was C0, not sure yet what that means.
The rest you can all leave as default unless you want to change the serial output settings, I lowered the baud to 38400 because slower speeds are more forgiving in most regards.
Regarding firmware upgrades etc, arduSimple does not recommend upgrading firmware on the Digi radios as it might mess up the config (can’t find reference now). So I decided to stay with ver 9007 which meant downgrading my new SX PRO but it worked just fine. It appears that XCTU downloads the firmware files for you so no need to get them yourself separately.