Modbus TCP/IP to USB hardware and software development

Modbus TCP/IP to USB hardware and software development


Job Description

I'm an iOS developer and I need to integrate an iOS app with a modbus slave over a TCP/IP connection.

I need an electrical engineer/developer to design a hardware/software interface between the USB on the iOS device and modbus slave (normally a PLC) using an inexpensive programmable controller (e.g. Arduino, Teensy, etc). Bluetooth might also be an acceptable method instead of USB which is something we can discuss.

I'm paying for this out of my own pocket so my resources are limited. I can pay hourly or with a fixed cost, but since I'm concerned about scope creep a fixed cost might be preferable as long as we can agree on the milestone and payment schedule.

The deliverables for this project would be:
1) A circuit design and/or code for a programmable controller that can interface between the modbus device and the iphone. Prototyping a PCB could also be involved.
2) Objective-C, C or C++ example code to control the modbus interface. Ideally this would use the Apple public frameworks but I'm open to suggestion.

This would be my ideal solution:
You would provide me with a Cocoa compatible Obj-C class and function such as the following:
[modbusHardware readRegisters:@["%R10010","%R10020"] completion:^(NSDictionary *regValues){
//do stuff asynchronously after completion

Then you would provide me with the hardware - circuit design, source, etc. Your hardware will have a USB and an ethernet port. The iOS device gets plugged into the USB port. The modbus slave (probably a PLC) gets plugged into the ethernet port. When I run the above command it will request data from the modbus device. When the operation is completed it will run the completion block.

I'm not looking for anything more complex than this right now. We would like to implement some other features such as data buffering on the device and encryption keys, but that's a long term plan and I need to keep it out of the first revision. Just keep in mind that if you get the job you will probably be hired to make changes again. That said, I am a developer so expect me to review and edit source code as necessary.

Note that by "modbus device" I generally mean PLCs. I'll have to test compatibility with different types of PLCs so if you have access to this kind of hardware for testing that's a huge plus.

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