Kenny Kerr

Anyway, about the RTS, I'd avoid to modify the driver for the TX-enabling. I'd prefer to manage "manually" the line...

Hi Mario,

Yes for the netduino it’s probably simplest to let the chip think it’s an RS232 and handle the RTS manually. We’re just going to use native code with our own board, so we can use the RS485 driver.

Cheers,
Kenny

FYI, I'm working to do the same thing, but for connect the Netduino+ to a PC.

Thanks Mario,

Did you get it to work? From reading through the Atmel docs on their USART and looking at the Micro Framework firmware (native code) it looks like the Micro Framework hardcodes the USART to operate in “normal” mode but we require it to be switched to “rs485” mode to ensure the right RTS behavior. Unfortunately this requires a recompilation of the netduino’s firmware to flip this register value.

Cheers,
Kenny

What RS485 transceivers are you using? If using RTS/CTS, you generally need to wire _both_ RTS and CTS.

I'm using the LT1785 tranceiver. I thought I didn't need to wire up the CTS but I could be wrong.

Also, are RX and TX swapped between the two boards (RX1<->TX2 and RX2<->TX1)?

I'm not sure what you mean. I tried to wire both board identically: DI to TX (pin 3) and R0 to RX (pin 2).

Cheers,
Kenny

If you're doing heavy development, I'd recommend picking up the Atmel AT91SAM7X-EK devboard, solder a 512KB MCU onto it, and buying a nice compiler and JTAG unit. These can range in price from low-cost (GCC and one of the low-cost JTAGs) to really nice (the ARM RVDS compiler and RVICE JTAG...about $10k). We use the latter, but you can certainly do this sort of thing using GCC and Netduino on a budget if you don't mind using printfs for debugging...

Could you recommend a basic JTAG unit for single-step debugging that I could use with GCC? I want to get a feel for what this is like with a microcontroller, but have no idea where to start or where to purchase such a thing.

Cheers,
Kenny

Thanks Chris - that sounds promising.