ECIO40 running on External Power

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Audette
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ECIO40 running on External Power

Postby Audette » Wed Mar 03, 2010 12:06 pm

Hi Guys,

I've got an ECIO40 development board with the PIC 18F4455 chip onboard. I want to connect it to an external 5V power supply. I've set the jumper to EXT, connected 5V to VDD_IN and both VSS to ground and nothing happens. The onboard LED doesn't come on like it does when powering from USB, and it doesn't seem to be working. what am I doing wrong here? I've not put in any bypass capacitors externally as they seem to be on the development board itself.

Another question I have is, once I have the ECIO board powered externally, and if I want to program the PIC chip or to read data out of the PIC chip, do I need to power it from USB or can I do it whilst being powered externally??

Thank you in advance for your help.

- Audette

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Re: ECIO40 running on External Power

Postby Benj » Wed Mar 03, 2010 2:22 pm

Hello Audette,

The LED on the ECIO40 device is controlled by pin RE2 on the 18F4455 device. When the USB is plugged in the LED is powered from a combination of the USB connection and from the output pin.

When using external power the LED will not light up as it is simply not being driven by anything. If you make the pin E2 output high then the LED will light.

You should also be able to reprogram the device and communicate with the device over USB while using the external power supply jumper setting.

Audette
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Re: ECIO40 running on External Power

Postby Audette » Wed Mar 03, 2010 3:21 pm

Hi,

Thank you for your reply. I have the Jumper setting to External, and powered the ECIO board via a DC 5V supply. I have an internal clock generated via the PWM and sent to pin C2. I've looked at that pin using an oscilloscope, but the value of the pin is 0 and will not give a clock output. All other outputs are the same. I know the Vdd in is getting 5V. Do I need to connect Vdd out too??

Is there a setting within configuration or registers of the PIC that needs to tell it that it has got external power? I can't think of anything else to do to get the board to power up :cry:

I should also say that the code works while plugged into the computer... its when I try the external power that nothing happens.

Any help would be appreciated .

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Re: ECIO40 running on External Power

Postby Benj » Wed Mar 03, 2010 5:18 pm

Hello,

The ECIO may be stuck in bootloader mode. When the USB cable is unplugged try resetting the device and it should start running your program. The only reason I can think of the ECIO to not run its program is if it thinks that the USB connection is present but cannot find device drivers ie if pin RE2 is held high. Have you got anything connected to pin RE2 that may be giving a logic high signal on startup?

The Ext power pin does not have to be connected to anything though you could maybe try to drive an LED from it to make sure that the power is making it through the board.

No configuration registers required to specify the external power just the jumper.

With the jumper in the EXT position and your external suppy attached can you reprogram the ECIO? If so then the device is definatley being powered and also running via the external suppy.

Might be worth placing a 10uF or a 100uF electrolytic capacitor across the ECIO power rails to see if this helps. I have had to add this to certain applications where there is a ot of current being drawn. EG high brightness LEDs or Motors etc.

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Re: ECIO40 running on External Power

Postby Audette » Wed Mar 03, 2010 5:53 pm

Hi Ben,

I've tried resetting the the device while plugged to the external power supply - but still nothing happens. While in external power, if I connect the USB cable, the onboard LED lights up, but I cannot program the chip. I've tried to reset it while connected, but nothing happens (LED doesn't blink after reset).

I will check the status of RE2 and let you know - but nothing should be driving the pin. I tried to comment out all of my code and just have the PWM generating the clock signal - but still no joy getting it to run via external power.

I will try putting in a capacitor and see if it makes any difference at all, but still I would've thought even in a high current mode the PWM should've worked and given the clock signal at the output port.

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Re: ECIO40 running on External Power

Postby Benj » Thu Mar 04, 2010 10:11 am

Hello

Are you powering the ECIO via the application board or are you connecting to it directly. The application board uses a 5V regulator and therefore must have an external voltage of 6V or more to allow for the voltage drop created by the regulator. I have just tested an ECIO here and providing an external voltage of 5V via the regulator was not enough for the device to power up as you are finding. However increasing the voltage slightly started the device running. If you are not using an external regulator then maybe you could try measuring the voltage being supplied by your DC supply to see if it is under 5V.

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Re: ECIO40 running on External Power

Postby Audette » Mon Mar 08, 2010 12:27 pm

Thanks for your help.

Seems to be working off the external power now.