CODESYS Status Bytes for RevPi Connect

CODESYS RevPi Connect Mapping Values


  • RS485ErrorLimit1: 10
  • RS485ErrorLimit2: 1000

If the standard values shall be modified, you have to assign the values in the corresponding POU.

The RevPi Connect modules have LEDs, three of which can be used freely. In addition, the watchdog and the relay can be controlled via the “RevPiLED” LED control byte.






If the bit is set to 0, the LED is off. At 1 it lights green.


If the bit is set to 0, the LED is off. At 1 it lights red.



If the bit is set to 0, the LED is off. At 1 it lights green.


If the bit is set to 0, the LED is off. At 1 it lights red.



If the bit is set to 0, the LED is off. At 1 it lights green.


If the bit is set to 0, the LED is off. At 1 it lights red.



If the bit is set to 0, the relay at connector X2 is closed, at 1 it is open.



To restart the watchdog timer, the bit must be set once to 0 and once to 1 within 60 seconds.

If one LED is red and green switched on at the same time, it lights up orange.

In the directory /home/pi/demo, there is the piControl.h header file in which PICONTROL_LED_A… is defined. A little sample program follows below.

The byte ’RevPiStatus’ contains the status of the piControl driver. Please note that a distinction is made here between I/O modules (DIO, DI, DO, AIO…) and piGate modules.



0, 0x01

piControl driver is running.

1, 0x02

At least one I/O module is connected that has not been configured by PiCtory.

2, 0x04

At least one I/O module by PiCtory has been configured, but it is not connected. The bit is also set if a piGate has been configured.

3, 0x08

An I/O module takes up more or less bytes in the process image than specified in the PiCtory configuration. This can happen if the version of the configuration file or the device description files used does not match the firmware in the I/O module. Get an update of PiCtory.

4, 0x10

A piGate module is connected to the left of the RevPi.

5, 0x20

A piGate module is connected to the right of RevPi. (Not possible with the RevPi Connect.)

6, 0x40

Current value of the input at connector X2. 0 corresponds to 0 V, 1 corresponds to 24 V.

Please note that only the desired bit in the byte RevPiLED should be changed. If you want to switch on e.g. LED A3 green, you can call PiTest -w RevPiLED,16. However, this switches off the LEDs A1 and A2 at the same time. You have to read the current value, change the desired bit and then write back the whole byte.

In C, you can use an ioctl call that does just that. The following example also switches LED A3 green on, but leaves the other LEDs unchanged.

int hd;
SPIValue sPIValue;

sPIValue.i16uAddress = 116;
sPIValue.i8uBit = 4;
sPIValue.i8uValue = 1;
ioctl(hd, KB_SET_VALUE, &sPIValue);

The status byte “RS485 Count” controls the communication with the I/O modules. This is interesting for you if you want to integrate your own devices into your system.

The RevPi I/O modules (AIO, DIO, DO, DI, MIO) exchange data with the RevPi via a serial line. The data is transmitted electrically according to the RS485 standard.

The piControl driver scans which modules are connected during startup and reset. It then communicates cyclically with the modules in the order in which they are mounted on the DIN rail from left to right next to the RevPi. First, piControl reads the output values for the respective module from the process image and sends them to the I/O module. In response, the RevPi receives the input values and writes them into the process image. Then it does the same with the next module and continues sequently.

Although RS485 is insensitive to interference, it can still happen that the data is disturbed during transmission between RevPi and IO module. piControl has an internal error counter for each module. If a transmission error has occurred, the counter is incremented. The maximum value of the counter is 255. As soon as a telegram has been transferred correctly between RevPi to IO module and back, the counter is reset to 0. The first error is ignored, i.e. only if two or more errors occur in succession the following error handling will become active.

The value RS485ErrorCnt contains the sum of all errors. The value can therefore be between 0 and 255*n if n I/O modules are connected. At the end of each cycle, the error counter is compared with the two limit values RS485ErrorLimit1 and RS485ErrorLimit2. If it has reached RS485ErrorLimit1, a message is output in kern.log. In the next version of piControl, the default values defined in PiCtory are written to the process image. If the error counter has reached RS485ErrorLimit2, the piBridge communication is stopped.

If one of the values is set to 0, the respective check is deactivated.

RS485ErrorLimit1 is set to 10 and RS485ErrorLimit2 is set to 1000 as default.