Propeller + Max3443 = 921kbps?

Greg Norton

I'm trying to communicate with a device over rs485 that specifies it needs 921,600 baud with 8N1 formatting. To this end I've got a MAX3443 driver chip, but none of the obex objects I could locate seem to support this rate. I know spin won't go that fast, and since I'm a novice at assembly so I was hoping to find something in the OBEX that would do the heavy lifting for me.

Anyone have an easier method? It seems I'm on the path to rolling my own solution based on some of the other forum posts I've seen regarding high speed serial comms. If it helps, the data will be sent intermittently in chunks of about 10 to 20 bytes at a time so only minimal buffering is needed.

Any input is appreciated.
Greg

Peter Jakacki

Much higher speeds are readily achievable but not so if you want full-duplex running in the one cog. Most communications are inherently half-duplex anyway in the form of command/response as is RS-485 which should only be 2-wire mode. Have a look at my Tachyon Forth especially the serial I/O methods which I am communicating with at 3M baud and faster speeds are only limited by the interface chips, in this case the FTDI USB doesn't run at 3.5M and 4M speeds which are the next highest speeds in Minicom.

Mark_T

That should be doable in PASM - are you wanting to send, receive or both? At 80MHz system clock then a bit-period is 87 clocks to with 0.3%

I suspect if there's a serial driver out there using PASM it will easily be adaptable to that baud rate (by someone knowledgable in PASM).

Greg Norton

Thank you both for your replies.

I found Peter's code for doing serial tx and rx, I'll use that as the basis for my object. I only need be either sending or receiving at any one time, but have the capability to both (half duplex). Looks like I'm going to learn PASM after all.

Greg