Hey everyone,
I’ve got an LPC2106 and I’m trying to use it to control the EasyDriverV3 board (hereafter called the ‘ED’), both from SparkFun.
Both boards work flawlessly on their own. I can force the ED board to make the motor step by using a simple momentary pushbutton, but at 1600 steps/rev you can imagine it’s a bit cumbersome. The next step is to get the ARM to supply the pulses and control the motor.
I have code running on the board that controls one of the digital output pins, toggling it from 0V to 3.3V and back again. (Actually it’s about 3.27V, but what’s a few mV between friends?). But when I hook that output pin up to the STEP pin on the ED board, it seems to be pulled down to 0V regardless of the state of the output.
I know this little EasyDriver has been run directly from the Arduino (I’ve seen the video), and I’ve heard that it can be run straight from the PIC. I’ve used PIC’s before, and most of them use 5V on the outputs - I’m not sure about the Arduino, but I would assume it’s the same.
What’s the easiest way to translate a 3.3V output signal into 5V? This will be a high-speed signal too, so I can’t just toggle a voltage regulator. I could pull out one of my old Electronics books and look for simple transistor circuits, but I’m wondering if any of you Embedded geniuses know of a quick trick to make this work without any additional components.
[EDIT]
I set up the transistor circuit with a 2N3904 NPN transistor. I used a pull-up resistor to make sure I could switch from 5V and 12V down to zero. I tried both voltages. The circuit worked (verified with multimeter), but the ED wouldn’t respond. Just for giggles I pulled the transistor out of the circuit, and tested the ED directly. If I jumped STEP directly to +V (12V or 5V, both worked), it would step erratically. If I insert a resistor (the pull-up resistor from the transistor circuit) in line, it didn’t work. The presence of a simple resistor caused the ED to fail.
I thought that maybe the resistor was limiting the current too much for the ED to respond. To that end I tried progressively smaller resistance values. 10k, 1k, 10-ohms. I saw promising results on the 12V - 10ohm combo. The steps were faint, but they were present. During testing, I let the smoke out of the 1/4-watt resistor. No good. I could get a larger power rated resistor at very low resistance, but there has to be another way.
I also tried a DM74HC373 octal D-latch, which allowed the ARM to directly control a D Flip-flop, giving me a nice 4.75V transition. I measured this transition very clearly on my multimeter. But then when I connect that same output to the STEP input on the ED, it’s as though the transition doesn’t happen at all.
I’m very confused. I don’t think the ED is bad because it responds when I give it a direct voltage transition manually. As soon as I get the controller to do it automatically, it doesn’t work.
Anyone have any ideas? I must be missing something, just no idea what.
[/EDIT]
Thoughts?
Thanks in advance,
-eewestcoaster