OK, I know that this question has been asked multiple times, not just on this forum, but elsewhere as well, but since every issue has a different set of parameters, the problems are unique. So I'm going to ask it again :-)
I'm trying to design a 'stock level' display system for a warehouse. The warehouse has aisles with multiple racks and component bins. Each rack has about 10 bins. Each bin requires a digital display of the stock remaining. I require a total of about 150-200 display units.
For the display units, I had thought of using a PIC to drive 7seg displays. The PICs would be daisy-chained to a master which communicates the display quantity to each of the slaves. For now unidirectional comms are adequate, but providing a bidirectional system would allow for addition of sensors in future. I was thinking of using I2C for this, but noise and cable length are issues (the farthest bins will be 100m from the master). I also wanted to pass power (6-9v) along with the data cables (so I'd have just 4 cables - Vcc, Gnd, SDA and SCL)
Yes, RS485 is an option, but if I'm not mistaken, RS485 drivers are not 'inherently' bidirectional. A DIR pin needs to be toggled. Also, cable complexity increases (differential pairs for SDA/SCL). What if I use a 'booster' every 10-15 bins? A simple line driver? Would this work?
Or is is better to use 1-wire? Speed is not really an issue - 20kHz data rate is more than adequate.
Basic requirements: low parts cost - no expensive drivers, few components low cable complexity - just 4 wires if possible signalling speed not an issue
Ok, its 3am and I've been working on a Nokia 6100 display controller based on the 18F2550. It's going to be part of a larger project, and I'll eventually switch to the 18F_J micros. But I have a 2550 at hand so I'm using it. I've tried like mad but I just can't seem to get the USB bootloader to work. I've tried 4 upto now - Diolan's, UBW, and Microchip's HID and CDC bootloaders.
Obviously, I have to mess with the linkers and modify a few ports here and there (no port D on a 2550). Diolan's just won't compile. UBW compiles, Microchip's HID and CDC both compile. The PIC gets detected by PDFSUSB and the HIDbootloader program. When I reprogram the PIC through the bootloader and then read it back through PDFSUSB, I find that no code has been written to the micro. On the other hand, the HID bootloader just locks up halfway through writing, and then the bootloader code gets corrupted.
Funny thing is that I used to use the USB bootloader about 2 years back with no problems. Then I switched to ds30Loader. Now when I want to get back I just can't seem to figure out what my issue is :-/
If by tomorrow morning some kind soul compiles a hex for me I shall be exceedingly grateful. If not, I'll just get back to it tomorrow - maybe my brain has just frozen.
PIC18F2550, bootloader entry through jumper to ground on RB7, (no EEPROM mark required - Diolan bldr), 20MHz crystal, no status LEDs required.
I've got the media button strip from an old HP Pavilion http://www.laptop-guts.co.uk/images/HPD ... HSTRIP.jpg The buttons are capacitive touch buttons. There are 7 buttons and a 5 element capacitive slider (for volume control). I thought it would be very cool if I could figure out how to interface this so that it can be used in other projects. The problem is that the construction is chip-on-board type, and the chip is covered in epoxy, so I have no idea what chip is being used :-/
The PCB has got 'Synaptics' printed on it. The Synaptics website has no datasheets, but it does have a generic interface manual.
There is an FFC-like connector on the board with 12pins, out of which only 8 are connected.I've figured out which is ground (actually two pins are grounded - pins 7 - so that leaves 6 pins to figure out).
Another wire (pin 5) is connected through resistors to the anodes of all the illumination LEDs and it is the thickest trace on the board. Some of the LED cothodes are grounded. The LED cathodes on the slider and the 'mute' bi-colour LED go to the CoB chip. So this thickest trace seems like Vled.
After measuring the resistance from each of the pins to Gnd, one wire showed about 850ohm, reverse biased, and open circuit when forward biased with a DMM. This tells me that there's probably a reverse voltage clamping diode between this wire and Gnd (Diode forward voltage mode showed me 0.675v). Sounds like Vcc? This same pin (Pin 1) has got a series 22ohm resistor (yes 22, not 220 or 2.2k or anything else) leading to the chip. There is a capacitor on this to Gnd after the resistor. Could this be a reset with 22ohms and not Vcc? I'm assuming it is Vcc, with a small resistor to decouple power supply noise.
4 more pins: SPI? Or I2C with reset and interrupt. But how do I figure out which pin is which? All the 4 pins show a rapid increase in resistance and then open circuit when forward biased with a DMM (sort of like what happens when a small capacitor is charging up). When reverse biased, 2 pins (Pins 3 and 4) show a 1080ohm (actual diode voltage of 0.705v) and the other two pins (Pin 2 and 6) show 1160ohm (diode 0.725v).
I have a BP which I've used to toggle the pins. I connect what I think is Vcc (Pin 1)and Vled (Pin 5)to 3.3v. The illumination LEDs light up. Slider LEDs are off. Mute is orange. Taking one of the pins to a 'high' state turns the Mute LED blue. If this wire is left floating, the mute LEDs sometimes rapidly changes colour.
Sorry if this query seems so vague. Let me know if I can describe anything better.
I've attached at composite image of the board along with pins named. Sorry for the rubbish blending - Photoshop couldn't handle it so I quickly did it by hand.
Hey everyone! This is an old-ish project of mine, but I was hoping to tweak it a bit (with your suggestions!) and spin myself a new one sometime.
The board was intitally developed for a workshop in my University for microcontroller noobs. We built more than 100 boards. The dev board was used to teach soldering as well as programming to the participants, so to keep things easy a lot of board components are TH. The MCP2200 and the LM1117-5 were pre soldered.
The board uses the Arduino philosophy of 'stackability' and easy connection, so all the pins are broken out to female box headers. Machine pin headers are used to connect single strand wire, since I found that the box headers didnt grip single strand wire too well. Additionally, even if a 'shield' is present on the board you still have access to all the pins. So you could use a shield and a solderless bread board at the same time. 5v, Gnd and Rx, Tx from the MCP2200 are also broken out seperately so you could potentially use this as a USB-TTLserial converter with other devices. The board has a jumper connected to the MCP's RTS pins, which allows ds30Loader to software reset the PIC. A removable jumper was necessary because the MCP interferes with the reset line during ICSP.
This is v3 of the board. I've got a few boards of earlier revisions that I populated and I frequently use when banging together a project. I've already made several 'shields', the most recent one being an programmable audio trigger for a DSLR my friend has. I've attached an image of the POV shield I made in action.
All files are CC-BY-SA. Feel free to make changes and improvements. Would love if you give me shout when you do. (Pins and functions on both the Top silk and bottom silk are named as per the 16F882/886. While the board can be used for other 28pin PICs, please verify if your PIC's power and Gnd pins are compatible with this board)
I got my free MCP2200 breakout PCB well over a month ago in the mail, but the idiot that I am, I mistakenly thought that the breakout was for a SOIC '2200 (I happen to have lots of SOIC '2200s left over from a previous project). Turns out that Mr. Murphy designed the circuit board for a TSSOP '2200 :-/
So I placed an order with Farnell/Element14 (actually Kit-n-Spares for individuals/non-businesses in India) and waited patiently. Apparently some of the parts I ordered were backordered, so the order took forever to come. Having delayed this Free PCB build long enough, I soldered up the PCB as soon as the mailman delivered the shipment. Here are a few pics from the build:
[attachment=2]The bare PCB had some gummy residue left over from the tape that secured it to the inside of the envelope. A little iso-prop on a cloth removed all traces of the mess.
[attachment=1]Most of the parts were in my junk box, scavenged from old electronics. I didn't have all the components in 0805, so I used alternatives - 0603 1k resistors, caps and LEDs.
[attachment=0]The only thing that is a bit of an eyesore is the crystal; I didn't have the surface mount variant (and it wasn't available on Farnell), so I simply used the HC49-3mm that was at hand.
Regardless, the breakout works well, and I have another USB to serial converter!
For quite a while I've been really interested in the Bus Pirate and its features. I recently bought an XC9572 CLPD board from Seeed and realized I'd need a JTAG programmer. The BP has got some great firmware that makes it into a JTAG programmer. And since I've bombed several times at the Free PCB giveaways I decided to build one myself.
My BP is decidedly ghetto - hand soldered on vero board, and a wild mix of through-hole and SMD components. (Sorry, I'm newly registered and can't post a link till I'm at least 1 post old - so blog link in the next post)
Here are a few photos from my blog:[attachment=2][attachment=1][attachment=0]
