Beremiz connector which loads a dynamic lib and use it as a transport to PLC.
Dynamic lib
Dynamic lib gives us a serial transport with standart API/ABI. Libs internals may use sockets/pipes/files/devices/etc.
It can implement any transport that PLC vendor like, the only requirement, is standart API/ABI.
The proposed API/ABI is:
int handle_open (void ** handle, char * uri, uint32_t uri_len); //Returns zero on successfull connection creation
int handle_close (void ** handle); //Returns zero on success
int handle_read (void ** handle, void *buf, size_t nbyte); //Returns numer of bytes red
int handle_write (void ** handle, void *buf, size_t nbyte); //Returns number of bytes written
Where:
handle - an opaque pointer for transport control entity.
uri - a pointer to sockets/pipes/files/devices/etc name.
uri_len - URI length (yes we will try address possible buffer overflow).
buf - a pointer to data buffer used for communication.
nbyte - a number of byte to transmit/receive.
Beremiz connector
The connector itself implements serial connection protocol, we propose LPCManager or YAPLC/IDE protocols as a base.
It also should have standart Beremiz side connector API, if someone adds data buffering to connector it would be very cool.
We propose the following URI format for connector:
UNIDBG://Path_to_dynamic_lib//Transport_uri
Where:
Path_to_dynamic_lib - A path to dynamic lib file (I beleive it should be relative to some base dir).
Transport_uri - a string that will be passed to handle_open as uri.
So PLC vendors can implement any transport layer they like and they can use the same connector for different transports.
Issues
32/64 bit: 32bit python wants 32bit dll, 64bit python wants 64bit lib at least on Windowr(R).
Boot protocol: different vendors use different boot protocols (e.g. we use STMicros-bootloader for program boot) and different file types to boot their PLCs, we must design some common way to handle these differences.
Architecture
The connector consists of two parts:
Dynamic lib
Dynamic lib gives us a serial transport with standart API/ABI. Libs internals may use sockets/pipes/files/devices/etc. It can implement any transport that PLC vendor like, the only requirement, is standart API/ABI. The proposed API/ABI is:
Where:
Beremiz connector
The connector itself implements serial connection protocol, we propose LPCManager or YAPLC/IDE protocols as a base.
It also should have standart Beremiz side connector API, if someone adds data buffering to connector it would be very cool.
We propose the following URI format for connector:
Where:
Issues