search

yaacov / ArduinoModbusSlave

Modbus slave library for Arduino
ISC License
204 stars 74 forks source link

Holding Registers #57

Closed DpunktS closed 4 years ago

DpunktS commented 4 years ago

Hello I have described an Arduino pro mini ATmega328p with the full.ino in Arduino IDE. Now my problem I can not choose between digital inputs and outputs, the holding register always shows 255 when reading but writing does not always result in error: timeout with QModMaster and the digital pins stay on output.

ysmilda commented 4 years ago

When your EEPROM is empty before uploading the full.ino example all the digital pins should be INPUTS. This means that if you read the Input Status this should reflect the current state of the digital pins you defined. To change the pinMode you should write a 0 (input) or a 1 (output) to the corresponding Holding Register.

From your description I'm not completely sure what it is that you're trying to do.

DpunktS commented 4 years ago

yes at the very beginning all PINs were inputs. Then I wanted to write in the holding register. Writing always stops with an error and the next time the holding register was read there were 255 in it and all pins are outputs. how do I get the 255 out of the eeprom.

yaacov commented 4 years ago

This is the loop that read the eeprom https://github.com/yaacov/ArduinoModbusSlave/blob/master/examples/full/full.ino#L52

This is the line handling CB_WRITE_HOLDING_REGISTERS that changes the pinMode https://github.com/yaacov/ArduinoModbusSlave/blob/master/examples/full/full.ino#L210

so you can: a. set the eeprom to what needed before the loop in line 52 b. call the device with modbus write holding register to the address that will change the currect binMode.

DpunktS commented 4 years ago

I have now deleted the EEPROM again so that it is at 0. Nevertheless I cannot write 1 into the EEPROM with QModMaster. Error code: Illegal data value

ysmilda commented 4 years ago

https://github.com/yaacov/ArduinoModbusSlave/blob/4fbc8c155a5752e532990661089922e167586042/examples/full/full.ino#L201 This line should have a && instead of a ||. Small logic mistake that breaks this example. I'll make a merge request to fix this.