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I2C UARTs


#1

I need a bunch more serial ports for the next version of my Raptor/G400 system, 12 to be precise. I’m considering 2 options. The first would used tri-stateable RS232 transceivers (like a Maxim Max3244). 3 of the native UARTS on the G400 will be dedicated to instruments that I talk to all the time and don’t want to multiplex. The other 3 UART ports on the G400 would drive/receive 3 RS232 transceivers and I’d enable the one connected to the instrument I want to talk to with a GPIO line. Probably a better solution is to use an I2C UART. If someone has used one of these, I’d sure like to hear about your experience. If you have a driver that works that would be even better (I haven’t found one on Codeshare or Google). If your driver uses interrupts that allow me to use NETMF event handlers like I do with the native UARTs, I’d be your new best friend.

If anyone has other ideas, I’d be happy to hear them.

Thanks - Gene


#2

There is a module on creations.

https://www.ghielectronics.com/community/creations/entry/19

Not sure if you can get one (marked as unlisted).


#3

Maxim have a SPI to UART that might be worth considering.

This quad option would save a lot on board space.

http://www.maximintegrated.com/en/products/interface/controllers-expanders/MAX14830.html


#4

So we’ve done a bit of testing with several I2C UART evaluation kits and they seem to work fine but aren’t without their weirdities. Most weird is that I can only find one single channel UART part that has more than 4 unique address choices. Not good enough when I need to add at least 6. I’ve checked NXP, Maxim and Exar who are the main suppliers of I2C UARTs. Maxim has a dual UART with more than 4 addresses which I might just use if the Exar part doesn’t work out.

I’m staying away from the multi-channel I2C UARTs since the one’s I’ve seen share a single IRQ line for all the channels. That means my interrupt handler has to spend time querying each channel to see which one has data. That violates my self-inflicted requirement to do as little as possible in an event handler.

Anyway, our initial tests with a Raptor board worked fine and we’re planning on using them as daughter cards on the custom G400-S mother board we’re laying out now.

Cheers - Gene