-
Notifications
You must be signed in to change notification settings - Fork 1
Home
This is a tool to help you walk through the Power Driver Board circuit and debug it section by section. It works best with the driver board sitting on a bench, powered by a benchtop power supply and a digital scope or logic analyzer.
The tool is pretty basic and once I got to this point I was able to fix all the problems on my driver board, so I stopped development so that I could get my machine back together again. Sorry for the shortcomings but I wrote this tool out of desperation to get a machine working that was completely wrecked.
With the driver board hooked up to your computers parallel port, you need to at least power the 12V circuit. I used a benchtop power supply and connected leads to the +12V test point TP5 and the GND post TP6. You should set a reasonable current limit to protect the board. I set my supply to 0.7A. When the board is powered up it should draw less than 0.25A.
In the tool press the Init button to open the parallel port on you computer. If this fails there is either a permissions problem or your parallel port isn't at the default address 0x378. You can either change your computer or fix the software.
The procedure at this point is to work your way down from top to bottom and verify the circuits are working as we move through the schematic and stimulate more of the board.
I am using a digital mixed signal scope with analog channels and digital channels. I mainly use the digital (logic) channels to watch everything and will probe around with an analog channel when I find a problem.
I use my first three logic channels for Init, Strobe, and Select coming in from the parallel port. I connect at the outputs of U58, pins 8, 4, and 12 respectively. I trigger on Init rising edge.
I put a chip clip on U3 and connect to all 8 data pins on the input side.
All probes are grounded at the GND post together.
- Test INIT - Toggles the init signal only.
- Test STROBE - Toggles the strobe signal only.
- Test SELECT - Toggles the select signal. You might see data bits change when you press this.
- Test DATA - Test the data lines from your computer parallel port. Slide the slider to select which data line is driven high, the indicator is the data line that is being driven, 0-7.
- Test Control - If all of the previous are working, use this to test the control signal latching and decode, U7, U5, U2, U4, U6. Moving the slider will output a new control byte, from 0x0 to 0x14. The control is only sent once after a change, if you want to generate the signal again just move the slider or toggle the button. It is critical that the control decode logic works.
- Watchdog - Generate control signals to reset the watchdog and clear the BLANKING signal. If the blanking signal is set nothing else in the circuit will work, so this is essential. You can adjust the speed of the watchdog to see where your circuit will start to drop out. I think my starts to cut out at 1700ms, I haven't analyzed the 555 circuit to determine what is reasonable. This depends on the control signal decode of output 0x5 SW_COL.
- Read section - The last section is a collection of buttons to read back any of the control registers that are marked as inputs. When you press one of the buttons the read back value will be displayed in the text box area in hex. You should at least be able to read back the DIP switch settings.