I'd look for the LairdTech modules. (formerly Ezurio, more formerly TDK). I'm using the BISM2 modules for years now with good success. Configured properly, they operate as a cable replacement for a serial line. I can help you with the proper configuration for that.
A quick scan indicates that they need a wired host to configure them before use, is that right? I.e. you can't configure them by pins or over bluetooth. (But this would not necessarily rule them out for me).
Or is the configuration non-volatile so it can be done once during production. Is this practical for a RS485 node? What we want is to be able to send out a bluetooth "box" with our own cabling to connect to our RS485 instrument (which may have no UI).
Of course we will test it. The question is whether we have to add a separate wired interface to it just so we, or the customer, can configure the bluetooth part.
As I said a quick scan of the manual indicates that the defaults do nothing. I.e it looks like the device does not act as a bluetooth node at all by default. But if the configuration is non-volatile we can probably configure it during test, so that might be OK. But can the customer pair with it without a UI? Yes I am being lazy by not going through all the documentation to answer these points but it seems like Meindart has done it all already so might be able to give me some more pointers.
The configuration is stored in non-volatile memory and done by modem-style AT commands over the serial port. Once enabled through the serial port, the module can also be configured over the air. Switching the DSR line switches the module from command to data mode (or and escape sequence which lowers the data throughput). We configure them during production.
One caveat: don't use any speeds over 57600 baud without flow control to the module (CTS/RTS). I have seen some data loss at 115200 but I am not quite sure if it was the module, this test ran on an Mac, running a windows app in Parallels (virtual machine). But on 57600 the module will keep up easily.
I'm not sure if the module could drive the direction control signals of your RS-485 chip all by itself. You might need a small timer for that, triggered by the TxD pin.
OK, thanks Meindart. In particular I was thinking about the user being able to pair with the device, since I don't know much about the process. As long as the parameters are non-volatile I think we can preset everything else ourselves.
Yes, that is correct. But you still risk internal buffer overflows if you don't use flow control. That's what they say in the datasheet too. And again: I tested this on a virtual windows machine on a Mac. I have seen similar problems with this setup using UDP over one of the network interfaces. On a real windows machine, I can dump data as fast as I can to my device while on this virtual setup only 5 of the 50 UDP frames I sent came across to my device.
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