Use a Scenix SX/28 at 50MHz. IIRC, Scenix have a virtual peripheral
application note for 8 full duplex UARTS *in software*, on a single
chip. Cheaper than a PIC too, I'd imagine. Check www.scenix.com.

Cheers,

Ben

> I am new to PICs so please excuse any stupidity. I would like to design a
> MIDI "router". It would have say for INs and OUTs and allow you to route
> messages between the various channels on the INs and OUTs (e.g. route IN1
> Channel 3 to OUT1 Channel 4 and OUT2 Channel 5). I realise it is a fairly
> ambitious project to start with but I don't expect it to be easy or fast.
>
> At the moment I'm trying to devise a way of supporting that many MIDI ports
> (i.e. 8). I can think of two possible methods:
> 1) Use PICs such as the 16C74 that have USARTs.
>     One disadvantage of this is that no PIC has more than 2 USARTs thus for
> a 4x4 box I would need at least 4 PICs (probably 5, 1 to deal with moving
> messages between the other 4 PICs). Also, I'd need a fair few JW parts for
> prototyping and these don't come cheap (especially here in Australia). In
> this arrangement I guess I2C would be a good way of communication between
> PICs.
>
> 2) Use external UARTs
>     I am unsure of how this would work. How many UARTs can you "drive" off
> one PIC? How many I/Os do you need for an external UART? I gather an
> external UART can be used asynchronously by using the external interrupts on
> PORTB. So, I guess you're limited to 4 UARTs on one PIC.
>
> Another possible problem is that MIDI runs at 31250 baud so the UART must
> support this. I know the PIC USART can and I've heard SMC UARTs support
> 31250 out of the box( so to speak). I gather you can change the crystal on a
> UART to get other rates but is 31250 easy to do with available crystals? BTW
> the MIDI specs allow for a +/-1% on the speed so there a bit of room in
> which to use.
>
> In summary my basic questions are:
>     - Do either of these designs appear even slighly feasible?
>     - Is there a better design?
>     - Is interfacing a UART to a PIC possible/difficult/processor intensive?
>     - Is it possible to do 31250 on all UARTs? (Easily?)
>
> Sorry for the large ammount of info but I'm not sure what is/isn't relevant
> yet.
>
> Thanks in advance,
> Thomas Brandon.