Hi Charles,

I don't know how you are processing the input string from one USART. Possibly you are using some form of interrupt. If you are using DT's instant interrupt and in PBP then there might be a way. I haven't gone through DT's routines so well that I know all about it. But it does allow the use ASM and PBP interrupt routines for a same source at the same time. So here is the idea.

Keep a flag of yours which you set when a re-direction is necessary. Now say you have a PBP interrupt handler. Create another handler for the same Rx interrupt in ASM. If your flag is not set then just return from it by testing the bit. If set then execute your redirection code. Read the byte from one RCREG and put it to the other TXREG testing the hardware flags.

Now clear the interrupt flags manually and any of DT's flag to make II believe that all has been done. This would possibly prevent the PBP handler in the second priority list to be invoked. You may need some tweaking though for example if

DT's interrupt routine backs-up the PBP (reuse pbp) vars even when processing the ASM int. I am not sure about it. You need to go through them.

Now you can tweak DT's routine to add a few defines for the port redirection.

Since you are using a SNMP agent I believe it is some sort of round robbin multi tasking. So if you second USART is having its buffer full and busy TXing. And you cannot afford to block the code This all depends on the amount of traffic and if your application has scope. You may set-up small redirection ring buffer that gets triggered on successful transmission to find out if you have some more bytes left to be sent from the re-direction handler.