[En-Nut-Discussion] Ethernut II RS485 Communication

Tue Nov 9 22:58:24 CET 2004

Hi,

This posting actually helped me solve my problem too, BUT you do not need to
perform step 3, instead, use the NUTO/S Configuration tool and set the UART1
to Half Duplex, PORTD and Bit 5.

It works a treat!

Douglas.

   _____  

From: en-nut-discussion-bounces at egnite.de
[mailto:en-nut-discussion-bounces at egnite.de] On Behalf Of Zheng Anding
Sent: Friday, 14 May 2004 7:45 a.m.
To: Ethernut User Chat (English)
Subject: RE: [En-Nut-Discussion] Ethernut II RS485 Communication

Hi Dusan,

Thanks for your reply and kindly help. Actually I've figured out the
solution for Ethernut II RS-485 with the great help of Mr.Damian. Here I
would like to give my credit to Mr.Damian. I couldn't finish it without his
help.

It's a little bit difference from yours since I use Ethernut II and use
UART0 as RS232 and UART1 as RS485. I would like to contribute out since it
looks like so far I havn't seen any similar post. Hope this will help some
beginners like me to get into the board faster and save some time for more
other codes. The procedure are:

0. Follow the hardware manual to configure the UART0 as RS232 and UART1 as
RS485...;

1. Follow the hardware manual and decide which pin you want to use as a
toggle pin. Here I use PD5 which is set by shorten Pin1&2, 3&4 of JP2 on
board;

2. Take a look at board and find the correct screw pin for 485A & 485B. Here
I found a mistake on hardware manual that the position of RS485 A/B is
different from which is drawn in manual. Actually it's swapped. On board you
should read D(DC) - S(Shield) - A(RS485A) and B(RS485B). Hook up A(RS485A)
to High(+) and B(RS485B) to Low(-) of your own 485 device or RS232/485
converter;

3. Modify nut/include/cfg/modem.h. Since I want to use UART0 as RS232 and
UART1 as RS485. So what I did is comment out all the "define UART1***" under
"#if 1"except the following three definitions. Then change the UART0 to
UART1. And change the UART1_HDX_BIT value to 5 since I decide to use PD5 as
a toggle pin;

#if 1
/* Define half duplex for RS485 */
#define UART1_HDX_PORT PORTD
#define UART1_HDX_DDR DDRD
#define UART1_HDX_BIT 5
#endif

4. Since I use ICCAVR, I use nutconf.exe under \ethernut\nut to rebuild the
Nut/OS libs. After running this utility, all the new built libs will be
automatically copied into ICCAVR's library directory. You dont need to do
anything to copy by yourself;

5. Here are a piece of my initialization code which is working fine on
Ethernut II board. I'm using latest Nut/OS 3.4.2.

// More other includes files .....

#include <dev/usartavr.h>

int got;
FILE *uart0, *uart1;
u_long baud = 9600, flag = USART_MF_HALFDUPLEX;

NutRegisterDevice(&devUsartAvr0, 0, 0);
NutRegisterDevice(&devUsartAvr1, 0, 0);

uart0 = fopen("uart0", "r+b");
uart1 = fopen("uart1", "r+b");

_ioctl(_fileno(uart0), UART_SETSPEED, &baud);
_ioctl(_fileno(uart1), UART_SETSPEED, &baud);
_ioctl(_fileno(uart1), UART_SETFLOWCONTROL, &flag);

for (;;)
{
   got = fread(RecBuf, 1, 32, uart1);
   fprintf(uart0, "Receive %d bytes...\n", got);

   NutSleep(1000);

   fwrite(WriteBuf, 1, 11, uart1); 

   fprintf(uart0, "Write 11 bytes...\n");

   NutSleep(1000);
}

6. Rebuild All of your project and you should be able to use RS485 now.

BTW, you've to get the latest usartavr.c which I got from Mr.Damian and I'm
sure you can download it from somewhere else...

Let me know if I mistake anything or any questions about it. Thanks.

Regards,

Alex

Dusan Ferbas <dferbas at dfsoft.cz> wrote:

Hi Alex,

you need to modify SW. First is to enable direction pin toggling (see 1). 
Then properly initialize usart - use new driver and set USART_MF_HALFDUPLEX 
mode (see 3 below).

You can live also with original Nut sources if you will set speed after 
changing flow control mode. See example below.

You can omit setting speed if you use Damian Slee's bug correction. Look 
for it in discussion archive 17th February, 16th April (BugFix: Usart half 
duplex mode... )

Anyway: CVS maintainers what about to incorporate Damian's fixes ?

----
1) nut/include/cfg/modem.h

For RS485 you do not need RTS/CTS so only following has to be enabled. 
Whole block is by default "#if 0". Do not enable (allow define) for 
..._RTS/CTS_.... This adds more code and also processing within USART
driver.

#if 1
/* Define half duplex for RS485 */
#define UART0_HDX_PORT PORTD
#define UART0_HDX_DDR DDRD
#define UART0_HDX_BIT 4
#endif

2) recompile Nut/OS libraries with 'make install'

3) example of initialization: call as InitUart0(9600);

FILE *InitUart0(u_long baud)
{
FILE *uart;

//u_long cooked_mode = 0; /* disable 
replacing \n with \r\n */

NutRegisterDevice(&devUsartAvr0, 0, 0);
uart = fopen("uart0", "r+b"); /* select binary 
mode */

u_long flags = USART_MF_HALFDUPLEX;
_ioctl(_fileno(uart0), UART_SETFLOWCONTROL, &flags); /* due to 
bug in Nut/OS 3.5.0 do this BEFORE SETSPEED */
_ioctl(_fileno(uart), UART_SETSPEED, &baud);
//following is set automatically when binary mode is selected
//_ioctl(_fileno(uart), UART_SETCOOKEDMODE, &cooked_mode);

return uart;
}

>But I cann't get anything from my slave device so far. My questions are:
>
>1. Is there anything special for the hardware se tting? Did I setup my 
>board correctly?
>2. I knew the 485 on Ethernut is half duplex and have to use PD5 / PD4 to 
>control the data direction, but based on Nut/OS, do I still need to do 
>this? Is there any existing RS-485 UART driver for Nut/OS now?
>3. If the above answer is NO, do I have to wirte ISR for Mega128 to send 
>and receive package?
>
>Thanks for any kindly help.
>
>Sincerely,
>Alex

Dusan Ferbas
www.dfsoft.cz 

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