I assembled the PIC LCD Backpack PCB I got the other day. Here are some pics. Behold:
[attachment=3]
I didn't have an SMD crystal, but fortunately, I was able to bend the leads of a PTH one and solder it on there anyway, since it was about the same size (aside: it would be cool if there were some "combo" PCB footprints to make prototyping easier, like a crystal with pads that would work for SMD and holes for the PTH version, combo resistors for PTH or SMD of various sizes, SMD vs TO-92 transistors, etc. does anyone know if these exist?):
[attachment=2]
I also didn't have a 220nF 0805 capacitor, but I had some 100nF and a 22nF. I put two 100nF's on their edges, side by side, and stuck the 22nF on top, so they're all in parallel (and therefore, their capacitance sums to ~220):
[attachment=1]
I had a grab bag of misc. pots, but fortunately, there were some 100 ohm ones (for the backlight) and a single 10K (for the contrast). Too bad they weren't facing the same way...
Here's some proof it actually works. I had to rework it, due to a bad joint on the contrast pot, and inadequate sockets for the display:
[attachment=0]
>>it would be cool if there were some "combo" PCB footprints to make prototyping easier, like a crystal with pads that would work for SMD and holes for the PTH version, combo resistors for PTH or SMD of various sizes, SMD vs TO-92 transistors, etc. does anyone know if these exist?):
look at the qfp prototype boards there is combo smd and pth hc-49 on it,
http://dangerousprototypes.com/docs/Dan ... oto_boards (http://dangerousprototypes.com/docs/Dangerous_Proto_boards)
i often find myself bending to-92 transistors in weird configurations trying to make them fit in small places.
Nice work, thank you for sharing.
I didn't have an SMD crystal, but fortunately, I was able to bend the leads of a PTH one and solder it on there anyway, since it was about the same size (
I do this all the time too. There is a footprint for this in the QFP protoboards.
I also didn't have a 220nF 0805 capacitor, but I had some 100nF and a 22nF. I put two 100nF's on their edges, side by side, and stuck the 22nF on top, so they're all in parallel (and therefore, their capacitance sums to ~220):
2x0.1uF would be fine, no need to be that close. I don't have 220 either, I just use 0.1uF now.
For the contrast pot: there is the option to control it with PWM for automatic contrast adjustment. I think the jumper SJ1 needs to be soldered one way or the other though, either for PIC control or simple POT control. I forget if we added a break trace, and I couldn't see if you soldered it. You can see it on the picture on the wiki:
http://dangerousprototypes.com/docs/PIC ... Prototypes (http://dangerousprototypes.com/docs/PIC_LCD_backpack#Prototypes)
BTW: Thanks for completing the free board. Your next 'unlimited PCB' coupon is in you PMs.
Hi schazamp,
Nice job on the assembly!
I just finished one today. My preliminary checks indicate that my board is at least partially working as my programmer recognizes the 18F2550 device, and I can load code on the PIC. Nothing happens, however, when the board is plugged into a USB port on my PC. It does not seem as if Windows has recognized that a new device has been attached. I'm wondering which code you burned into your chip? There seems to be a couple of .hex files available with no info to distinguish them. I'm assuming that the 'Dump' version includes both the bootloader and the PIC-LCD code, so that is what I loaded. What did you use?
Also I noticed that you soldered the 0.22uf capacitor to 'C4' on the board. Looking at the schematic, it looks like C4 is supposed to be just a 0.1uF by-pass capacitor, and that the 0.22uf cap is supposed to be on C3, the Vusb filter cap. Then again, your board seems to be working, and mine is not!
I rung-out the D+, D-, Vcc and Gnd connections from the end of a USB cable I attached to the board all the way back to the PIC pins because I was suspect of the USB jack solder connections, but everything was OK. There does not appear to be any shorts on the board either!
I did notice one minor error on the backside silkscreen. The ICSP connector has a pin labelled '3.3V' when it should be labeled 'Vcc'.
John
Hi John,
Thanks for the update, I'm sorry it's giving you problems.
The DUMP firmware is both bootloader and firmware, it should be a one-shot program. Make sure you;re programming the configuration words too.
If you jumper PGC and PGD does it connect as a HID USB bootloader?
You are correct - C4 is 0.1uF, C3 is 0.22uF. Sorry about the incorrect silk, it is probably a hold-over from the 3.3volt version we made too.
The only parts absolutely needed to make the USB connection:
D1 and R1
C1, C2, Q1
F1
Hi Ian,
Thanks for the reply!
Hmmm, are the configuration words programmed separately? The 'C' compiler I normally use for my projects is from CCS. When it generates the .hex file, the configuration bits are part of the file. My programmer (also from CCS) reads the .hex, and takes care of everything (code and configuration) seamlessly. In the case of the PIC LCD, I just selected the "Dump" version of the code, and burned it to the PIC. The programmer appeared happy with that.....
I don't think the firmware is running on my board. Windows does not recognize the board when it's plugged into a USB port with/without the PGC and PGD shorted together.
I haven't checked (with a scope) to see if the oscillator is actually running, but I won't have an opportunity to do that until Monday. All the component values are OK, and there does not appear to be any poor connections or shorts, and the MCLR pin is being held high. If it's programmed properly, it should run! I can't think of anything else to check?
BTW, everything is populated on my board except the LCD specific components (ie. the pots and the transistor). I'm planning to use this board for a slightly different purpose once I get it running, so they aren't needed.
John
You could program a simple program that toggles a pin every second and connect that pin to a led.
If the LED flashes every second the oscillator is working and the config words are setup right :) No need for a scope.
Hi Sjaak,
Yes, that occurred to me as well, but at the moment all my development tools are at the office, and I won't get back to them until Monday morning. As a matter fact, almost all my designs use an LED connected to a I/O pin so that I can flash the LED at power-up to indicate that the PIC is running!
In the meantime, I guess I was just wondering if there are any differences in the way code is compiled and burned to the PIC using the Microchip compiler vs. the CCS compiler.
Thanks,
John
The compiling and programming process is the same for most PIC development tools, it sounds like you've done it before and have it down. Sometimes people use old programmer tools like WinPIC800 and serial port programmers, they often had a check box to program the config words or not.
My guess now is that the D+ and D- USB lines are shorted under the USB mini-B connector. This happens to me quite a bit, and new boards use an updated footprint that is easier to hand solder. If you have hot-air try to pop it off. If not, squirt down a bunch of flux and mop it up with wick, add more solder and mop it up too if that doesn't work.
Hi John, nice work.
A bit late, but to answer your questions:
[quote author="ezflyr"] I'm wondering which code you burned into your chip? There seems to be a couple of .hex files available with no info to distinguish them. I'm assuming that the 'Dump' version includes both the bootloader and the PIC-LCD code, so that is what I loaded. What did you use?
[/quote]
I believe I burned the bootloader, then used the firmware update utility. I don't remember exactly, I tried a few different things before I got it to work.
[quote author="ezflyr"] Also I noticed that you soldered the 0.22uf capacitor to 'C4' on the board. Looking at the schematic, it looks like C4 is supposed to be just a 0.1uF by-pass capacitor, and that the 0.22uf cap is supposed to be on C3, the Vusb filter cap. Then again, your board seems to be working, and mine is not!
[/quote]
Hm, good catch. I, obviously, didn't notice that. It still appears to work, however, like Ian's note, he's had success with just 0.1uF on the filter cap.