I am trying to use the 28035 controlCard along with the TI ISO3086DW 485 transceiver.
I see a few things that do not make sense to me:
- If you look at the schematic of the controlCard (I am looking at release 0.2 - downloaded straight from your website an hour ago), you see a 3.3V Vcc for the SCI ISO IC (driving Tx-ISO and Rx-ISO signals), but when I put a scope on the Tx pin on the J3 header, it outputs a ground-centered +5V/-5V (10V Peak-to-peak). Is this correct or did I break something perfectly? Two of my boards do this.
- The ISO3086 chip only sends out 0 to Vcc (in my case 3.3V) serial signals, will this work with the J3 Rx pin? Right now, pumping 0 -> 5V data to that pin (verified by scope) just produces a bunch of framing errors in the SCI Rx FIFO. I am not sure if my timing is off or if the signal needs to be amplified.
If I connect two controlCards together (Tx <->Rx), using one with my code and the other that just outputs data out of the SCI (J3 Tx); everything seems to work fine.
I am not married to the ISO3086 solution (though I prefer this since I have a bunch on hand) but I am engaged to RS485. What do you suggest for an RS485 interface to the controlCard?