UART/SPI to RS232/USB-B

Projects General Guidance
1

Hi guys, total rookie here. I'm working on a project that involves having an Arduino mega communicate with two syringes that each have an RS-232 port and a USB-B port. My original plan was to hook up two serial ports from the mega to MAX232s and have them connect separately to the two RS-232 ports. However, I'm trying to consider other options.

The USB-B can use TTL levels to communicate, which seems like a nice workaround, but the mega only has one USB port. I have a feeling I can't communicate serially to two different devices using a USB splitter (or can I?). I don't know a lot about USB protocol and it seems pretty complicated, so any help here would be much appreciated.

I'm also considering using an SPI connection to communicate more cleanly with both syringes, but given that they're looking for serial inputs, I have a sense that won't work. I guess I could probably convert it back into two serial outputs, but at that point I'm better off using the actual serial ports, right?

2

Stick with serial. The other options won't work.

3

Add Serial/RS232 adapters. Simpler than adding USB host capability for the USB slave devices to connect to.

Examples:

http://www.nkcelectronics.com/rs232-to-ttl-converter-board-33v232335.html

http://www.nkcelectronics.com/RS232-to-TTL-converter-board-DTE-with-Male-DB9-33V-to-5V_p_369.html

(forum might add some extra characters to the start and end of those)

4

The mega has a total of 4 serial ports, of which 3 are not committed. One is used for debug the others are open. It appears to me serial is the easiest and there are libraries that will have most of what you need already finished. This response is to help you get started in solving your problem, not solve it for you.
Good Luck & Have Fun!
Gil