5473

Mini PLC ideal for model trains and small hobby (automation) projects

STM32F407VGT6 Discovery board

Easy to program

Ideal for model building or other hobby applications

Cheap

16 digital inputs
16 digital outputs

can be expanded to:
64 digital inputs
64 digital outputs

4 PWM outputs (hardware PWMs do not take up processor time)
 frequency can be set per PWM

64 internal markers

64 internal counters
 counter_up input
 counter_down input
 counter_reset input

 counter_up output 1 if count value reached
 counter_down output 1 if count value 0

64 internal timers
timer input
 timer_reset input
 timer_output 1 if set time reached
 adjustable between 0.1 second and 99:59:59:90

TMR56 to TMR63 continuous timers
 deliver square wave of set time if input 1

Due to the limited dimensions of the screen, programming can only be done using Arduino logic

&&     AND
||        OR
^        XOR
!         NOT
( 
)
/\       RISING EDGE
\/       FALLING EDGE
= 
SET
RST

Cycle time adjustable between 10 milliseconds and 100 milliseconds (hardware timer interrupt)

To keep the Timer seconds the same as real seconds set to:
 10 milliseconden
 20 milliseconden
 25 milliseconden
 50 milliseconden
 100 milliseconden

Program can be saved in the FLASH memory of the STM32F407.

16000 bytes of freely programmable memory

Maximum 1000 lines.

The number of lines and the cycle time are determined by the number of bytes per line.

Each program line can be a maximum of 20 bytes long (screen size and RAM storage capacity limitation)

with maximum usage of bytes in each line, the maximum number of lines is 800.

bytes per instruction :

1 byte
&& || ^ ! = SET RST ( ) /\ \/

2 bytes
INxx OUTxx Mxx TMRxx CTRUxx CTRDxx TMR_Rxx CTR_Rxx

3 bytes
PWMxx %% PWM number percent output

Cycle time depends on the number of selected inputs/outputs and program length

time required for 16 inputs/outputs without program
110 microseconden

time required for 64 inputs/outputs without program
437 microseconden

average time per instruction
1.5 microseconden

For full use of the program space with 64 inputs/outputs, 50 milliseconds should be more than sufficient.


437 microseconden + (16000 instructies * 1.5 microseconden) = 24437 microseconden.

Inputs are read at the beginning of the program

Outputs are calculated during the runtime of the program but only written to the outputs at the end of the program.

Program line processing without brackets is done from left to right.

Program line processing with brackets, first all logic within the brackets from left to right until all brackets are processed and then the entire line from left to right.

Automatic restart of the program if saved in FLASH and prog/run switch set to run.

See on Github

https://github.com/thieu-b55/STM32-mini-PLC