I have made quite a bit of changes since I made the block diagram and one of the changes happened to be what you suggested. I no longer am using the SPI bus and I got rid of the ADC. (The LCD doesn't support I2C btw, so I would need some controller inbetween to go from I2C to parallel or SPI)kamdy said:From the block diagram of the system you are using two buses I2C for the camera and the Fuel gauge and the SPI bus for the ADC and the LCD. I suggest using ADC and LCD with I2C bus instead of the SPI bus. This will minimize the number of pins and the software of the FPGA
The following URL might helpfreeskier89 said:I have made quite a bit of changes since I made the block diagram and one of the changes happened to be what you suggested. I no longer am using the SPI bus and I got rid of the ADC. (The LCD doesn't support I2C btw, so I would need some controller inbetween to go from I2C to parallel or SPI)
haha... I am so glad you pointed that out! I forgot a power switch. That would be bad to get the boards back and figure out that the device would always be on. Hmm... I am going to have to think on how I want to do that. What do you think of using a SCR and that is triggered by a single pushbutton for powerup, and then MCU would shut off power with a power NMOS. I attached a schematic. Is their a distinct advantage of using P channels?hjames said:One other thing since this is supposed to be a portable device - power-on/soft-off is something that you should figure out how to implement. A simple PMOS pass transistor spliced into the VCC line, and a spare line (maybe replacing one of the switches you alread have). Another way is to jerry-rig all the enable lines of the power supply chips, but this would be trickier since the LM2704/boost converter is sitting directly on the VCC line.
Yes and no. This is where this device starts differing from a normal digital camera. If I could get ahold of some really powerful UV LEDs(ones that emit as much light as a normal mercury vapor blacklight) then I would be really really happy to use them, but the most I can find is a 200mW $300 Power UV LED from Nichia. That will obviously not work. I am planning on using a xenon flash tube and then running the light from that through a UV transmissive filter (section of a blacklight tube). If you happen to have any ideas regarding UV illumination I would be very happy to hear because, right now, that is the sketchiest part of the project.hjames said:Two other comments - have you looked into using LEDs instead of the flash tube?
Oooo... That looks very nice. I wish I would have seen that earlier. Oh well, I think the current setup will be fine for now.Also, https://www.electro-tech-online.com/threads/ftdi-vdip1-eval-kit.25544/
Seems to be a new chip out. This would significantly change your design, so I'm not sure if it's worth it or not.
True. That sounds like a good idea.hjames said:Well, you'll need to decide whether you want to disconnect the DS2764 when you power down the device or not - it'll reset the battery capacity gauge when ig gets disconnected.
The main problem with using N-channel FETs is that disconnecting ground leads to some issues if you have to interface logic on the battery side... In any case, it's better to have the power switch temporarily trigger the gate of the pass mosfet - long enough for the PIC to override the switch and maintain power to the circuit.
I need something that is 370nm or lower, and they need to be pretty powerful... I have tried an assortment of UV led's and they do not cut it. I might be able to put together an array of 365nm leds together though.hjames said:400nm LEDs are available - $1 each, direct from the manufacturer...
**broken link removed**
Lumileds has a 600mW 460nm LED, which is definitely in the visible region.
Digikey used to carry some 370nm LEDs, but looks like they stopped.
freeskier89 said:Well, im not using a bunch of dev/eval boards because the whole point in making the board was to show that it could be portable and low cost (component costs) and also so I could learn a lot from it. I think that the firmware will take some time, but I am a WAY better programmer than electical engineer. For that reason, I thought I would dwell on custom circuitry. I guess I do not see how using a core would cut development time. I would rather have the system be optimized to begin with rather than throwing something together that is rough and then trying to patch it up later.
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