Hello,
First of all let me say that I love Pololu’s products.
I’m giving my first shot at building a project that involves controlling a motor from a PC. I ordered the Micro Dual Serial Motor Controller and USB-to-Serial Adapter. https://www.pololu.com/products/pololu/0391/ https://www.pololu.com/products/pololu/0410/
Correct me if I’m wrong but this seems to me to be the easiest way of doing such a task.
My first question is regarding the correct wiring of the USB to serial board to the motor controller.
I know for sure I need ground and the TX pin. I’m not sure which line to use for reset and also for power to the controller.
I would appreciate if someone can tell me the correct way to wire the two boards correctly.
My other question is the following:
All the examples in the manual are for PicBasic code.
Can someone point me as to how I can send bytes (commands) to the controller from a terminal like Hyper term ?
I want to play with it before I start to write code. Also configure it.
do I have to send hexadecimal or decimal strings ?
I know my questions are probably silly to the more advanced of you, but I’m just starting out and any help will be greatly appreciated.
Thanks.
The USB to Serial Adapter and Micro DSMC are a great little pair, and the normal connections are as follows, based on the pin numbers of the MDSMC:
Motor power supply - what it sounds like (i.e. batteries), or could conceivably connect to USB adapter VBus for VERY LOW POWER motors
Ground - Motor power supply ground AND USB adapter ground
Logic supply - USB adapter VBus (+5V)
Serial Control Input - USB adapter TX
Reset - USB Adapter DTR, RTS, or through a resistor (4.7KOhm or greater) to VBus
6-9 to your motors
Getting logic supply right from the USB VBus is just a little iffy. True USB specs should keep VBus within the allowed 5.5V, but it’s up to you if you trust your hardware. I do it with mine and have never had a problem, but I have seen some powered USB hubs that just pass the wall adapter voltage straight through to the USB ports, which is not a good idea. Your choice.
Entering command bytes by hand is very cumbersome, so I imagine you’ll eventually want to write a program that directly communicates to the serial port. You can do this from a program like labview or matlab, or I could post some code a friend wrote for Windows in C.
To start you will want a terminal program that allows you to set the numeric values of the bytes you transmit (i.e. not just ASCII characters, like Hyperterminal). The only program I know of to do this is RealTerm from SourceForge. Its pretty wonky, and in my experience the DTR and RTS set/clear buttons don’t actually do anything (like resetting your motor controller). From the send tab you will want to send strings of numbers, separated by commas, using the “send numbers” button rather than the “send ascii” button. Weather you do it in Hex or Dec doesn’t matter, 15=0x0f (=0b00001111, but I don’t think RealTerm reads binary).
So, for example, you might want to send:
0x80,0x00,0x01,0x7F
meaning:
start byte,DSMC device ID,motor 0 (always works) fwd,full speed!
What are your computer controlled motors going to be doing anyway?
Good luck!
