modbus_rtu_set_custom_rts problem

[gianlucads]

---

libmodbus version

libmodbus-3.4.1

OS and/or distribution

OpenWRT CC compiled for mips

Description

Hi used function modbus_rtu_set_custom_rts(), for manage trasmition direction using a gpio of my HW.

I insert this function in main modbus .....

 ctxRTU = modbus_new_rtu("/dev/ttyS0", 19200, 'N', 8, 1);
modbus_connect(ctxRTU);
modbus_rtu_set_custom_rts(ctxRTU, csetrts); 

..... and definited

void csetrts(modbus_t *ctx, int on){ int gpio = 20; printf("valore di on=%d\n",on); if (on){ SetOut(gpio, 1); } else{ SetOut(gpio, 0); } }

where function SetOut () set pin of my HW

but libmodbus never call csetrts for set my pin during polling, so i can't read answer to my polling

any ideas?

Gianluca

[stephane]

Do you check the return value of modbus_rtu_set_custom_rts to ensure it's working as expected? (0 means success). The RTS mode must be set with modbus_rtu_set_rts() to allow the call of your custom function: https://github.com/stephane/libmodbus/blob/master/src/modbus-rtu.c#L286

[gianlucads]

Hi, I check return of function...

`// printf("open modbus RTU\n"); ctxRTU = modbus_new_rtu("/dev/ttyS0", 900, 'N', 8, 1); // ctxRTU = modbus_new_rtu("/dev/ttyUSB0", 9600, 'N', 8, 1); //ctxRTU = modbus_new_rtu(mb->PortModBus, mb->baud_rate, 'N', 8, 1); //modbus_set_slave(ctxRTU, 1); modbus_connect(ctxRTU); //modbus_set_debug(ctxRTU,1);

// rc1=modbus_rtu_get_serial_mode(ctxRTU); // printf("modbus_rtu_get_serial_mode: %d \n",rc1); // rc1=modbus_rtu_set_serial_mode(ctxRTU, MODBUS); // printf("modbus_rtu_set_serial_mode: %d \n",rc1); res = modbus_rtu_set_rts(ctxRTU, MODBUS_RTU_RTS_UP); printf("modbus_rtu_set_rts: %d \n",res); // modbus_rtu_set_rts_delay(ctxRTU,1000); res=modbus_rtu_set_custom_rts(ctxRTU, csetrts()); //GPIO20 printf("modbus_rtu_set_custom_rts: %d \n",res);`

....... MDB TCP start loop modbus_rtu_set_rts: 0 modbus_rtu_set_custom_rts: 0 start loop rtu ........ seem ok, but not work. My bus schematic is

RXTX connect to chip RS485, and mode of trasmition connect at gpio 20 of my CPU

Do you have a example code for my problem?

ths

[zzeroo]

@gianlucadisimone What is the return value of csetrts()?

printf("csetrts(): %d\n", csetrts());

[Nykytas]

Hello!

I encountered the same issue. I called modbus_rtu_set_custom_rts(externalCtx, controlRTS), but controlRTS was never triggered.

I added a call to modbus_rtu_set_rts(externalCtx, MODBUS_RTU_RTS_UP); right after modbus_rtu_set_custom_rts(externalCtx, controlRTS), and controlRTS started being triggered.

Hope this helps someone!