Some say that handing out business cards is an antiquated practice due to the ubiquity of smart phones which can be used to trade or record contact information in mere moments. Instructables user [sponges] however, doesn’t agree and is pushing a “business card renaissance” of sorts with his POV business card.

Hand-built in his basement, the cards feature a handful of SMD LEDs that display his name, followed by his phone number when waved back and forth. Constructed to be nearly the same size as a standard business card, his verison uses a PIC to manage the display as well as a tilt sensor to monitor the card’s motion. His walkthrough is quite thorough, and includes tutorials for each of the steps required to build the card. He discusses constructing your own etching tank, converting a laminator for PCB transfer purposes, building a solder reflow oven controller, as well as hacking an aquarium pump for use as a vacuum-powered pick and place.

The end result is a sharp looking business card that ensures you won’t forget meeting him. Keep reading to see a video of the card in action.

It’s hard to let a Christmas go by without looking in on a geeky Christmas tree project. Luckily, [Peter Davenport] decided to share his Arduino and LCD shield tree.

Blinking USB dude

If you’ve got a 555 timer and some commonly salvageable components give this blinking LED man a try. The version above is USB powered but that’s just to take advantage of the 5V regulated power.

Propeller business card

[Jay's] business card is packing quite a punch with this Propeller microcontroller. We love seeing electronics design in cards (however unrealistic the price and portability may be), and this is a big processing upgrade compared to the Tiny85 based offering.

Flying high in NYC

We leave you with a spectacular view of New York City. This breathtaking footage is just as fascinating as the first videos we saw from these folks.

[Frank Zhao] put together a USB business card. It’s even got the instructions printed right on the silk screen of the PCB explaining how it should be used. He based the design around an AVR ATtiny85 microcontroller. It runs the V-USB package that handles USB identification and communication protocols. The rest of the hardware is pretty standard, the uC draws power from the 5V USB rail, with a couple of 3.6V Zener diodes to drop the two data lines down to the proper level.

Once plugged in it waits until it detects three caps lock keypresses in a row, then spews a string of its own keypresses that type out [Frank's] contact information in a text editor window (video after the break). It’s not as reusable as the mass storage business card because [Frank] didn’t breakout the pins on controller. But we still enjoy seeing business cards that make you stand out.

This is a great project to tackle with your newly acquired AVR programming skills.

[Thanks Harald]

Just snap off the corners and this business card can be used as a mass storage device. Well sort of. The tab left over has four traces on the back to make it USB compatible. The PIC 24FJ64GB002 microcontroller on the card registers as a storage device and launches [Ramiro's] resume and a cover letter loaded as an HTML file. He’s made it as useful as possible by including access to the SPI and I2C bus connections but he’s also included some firmware to act as a data logger or an oscilloscope. At about 5 euros a piece you won’t be distributing these willy-nilly but it’s not too much more than handing out breakout boards with your name all over them.

Embedded above is a neat augmented reality business card by ActionScript developer [James Alliban]. After seeing “the most impressive business card you will ever see“, he was inspired to update his own business card. His new card has a fiduciary marker on the backside and directs you to his site. A flash app on the site displays a video where he tells you more about himself. The 3D grid of planes in the video varies in depth based on the brightness of the section. He has a few more AR and tracking demos on Vimeo.

Updated: While we’re talking augmented reality, it’s worth checking out the tech behind ESPN’s baseball tracker that uses doppler radar.

Related: Augmented reality in Flash

[via Josh Spear]

Evil Mad Scientist Laboratories has released the 2313 target board. A business card sized development board for working with ATTiny 2313 microprocessors. We saw them at the Maker Faire, and thought they looked familiar. You may recognize them due to their similarity to the Atmegaxx8 family board. As usual, this is released as creative commons and source files are available on their site.

[John Park] has managed to snag a couple interesting business cards at Maker Faire. The first is Adafruit’s laser cut Spirograph card. The other is a ATtiny 2313 prototyping board from Evil Mad Science; it looks to be the same style as their well-known AVR target board. We’ve also heard rumors that [Jérôme Demers] has bunch of resistor bending cards.

For more business card nonsense, check out: [Goodspeed]‘s smart card emulator, [Mayer]‘s embedded gears, and our web server business card.

Evil Mad Scientist Laboratories has updated their business card AVR breakout boards to version 1.1. We suspect the changes will probably make them even more popular. The boards are designed for the ATmegaXX8 family of microcontrollers. The center has all 28 pins labeled while either end has a prototyping area. An in-system programming header is also provided. For the new version, both prototyping areas have been increased to accommodate DIP14 packages. The holes for the microcontroller are now larger so that they can hold a ZIF socket. Finally, the power and ground traces have been expanded. We’ve always like the versatility of these boards, as demonstrated in the Tennis for Two project, and can’t help wondering if these updates were made to facilitate another project.

This mini web server is slightly smaller than a business card. There are a lot of tiny one-board servers out there, but this is probably the smallest you can etch and solder at home. Unlike many embedded web servers, files are stored on a PC-readable SD card, not in a difficult-to-write EEPROM. Read on for the web server design, or catch up on PIC 24F basics in the previous article: Web server on a business card (part 1).

Concept overview

The goal of this project is to build a web server on a business card that serves web pages and files from a FAT formatted SD card. The server is based on a PIC 24F that connects to a TCP/IP network using the ENC28J60 ethernet MAC/PHY. Network layers and low-level services, such as DNS and DHCP, are handled by the Microchip TCP/IP stack. A FAT 12/16/32 formatted SD card contains web pages and files. A very simple HTTP server ties everything together by handling page requests on port 80, searching the SD card for requested, and serving them with the correct content type.

Hardware

(full size schematic .png)

Microcontroller (Microchip PIC 24FJ64GA002)

The brain of the server is a 16-bit PIC 24FJ64GA002 (IC1), a 28pin microcontroller available in several hobbyist friendly packages. Check out our PIC 24F introduction for more about working with this chip.

PIC 24Fs operate between 2 and 3.8volts, which is perfect because the ethernet chip (IC2) and SD card both run at 3.3volts. This chip has 8K of RAM, plenty for the TCP/IP stack and a few K for working with a full FAT file system. The 24FJ64 has two SPI modules, so the SD card and ethernet IC each get a dedicated data bus.

The PIC processor core operates at 2.5volts, and requires a 10uF capacitor (C2) for the on-chip voltage regulator. The datasheet specifies a tantalum capacitor, but we used a low-ESR electrolytic in a prototype without incident. Every power pin needs a 0.1uF decoupling capacitor (C4,5).

The internal 8MHz oscillator provides a 32MHz clock source with the 4x PLL multiplier enabled. We’re also using an external 32.768KHz crystal (Q1) with 2 x 27pF capacitors (C17,18) to enable the real time clock calendar.

Programming connections are brought to a header (SV1). We chose to use programming pin pair three (PGx3). The master clear and reset (MCLR) function is enabled with a 2K resistor (R1) from V+ to the MCLR pin. Optionally, add a button (S1) from MCLR to ground for a manual reset switch.

Ethernet connection (ENC28J60)

An ENC28J60 (IC2) handles the network physical connection (PHY) and MAC layer. The ENC28J60 needs a number of support parts beyond the typical 0.1uF decoupling capacitors (C6,7,9,10). A 25MHz crystal (Q2) and 2 x 27pf capacitors (C15,16) provide a clock signal. The internal core voltage regulator requires a 10uF tantalum capacitor (C1), but an electrolytic capacitor also worked fine. Two LEDs (LED1,2) with 330ohm resistors (R2,3) display link and data status.

A bias resistor (R12) is required; the value will depend on the ENC28J60 version you’re using. Current chips should be B5 (PDF) or B7 (PDF), and require a 2.32K 1% resistor.

The PHY I/O portion specifies 4 x 49.9ohm 1% resistors (R8-11), and a ferrite bead (L1).

The most difficult-to-find part for the ENC28J60 is the correct RJ-45 jack with integrated magnetics (RJ1). We used a J1006F21 PulseJack from Pulse Engineering. Be sure to check the pin configuration and connections if you use a different jack, they will probably be different than ours. A Cadsoft Eagle part library for the JP1006F21 is included in the project archive. This was a $4 part, but it’s gone up to $7. If you know of other jacks that work we’ll add them here.

microSD card

We used a microSD/transflash card in this design because SD cards waste a lot of board space under the holder. microSD cards are smaller versions of SD cards with the same data interface, and most come with an adapter for use in standard SD card readers. The card needs a holder (SD1) and a 0.1uF decoupling capacitor (C8).

If you want to use a full-size SD card, take a look at our version one prototype in the project archive. We used Alps SD card holder #SCDA1A0901. Unfortunately, this part is has been discontinued and we’ve yet to find a suitable replacement. Don’t try #SCDA5A0201, that’s for sure. If you have a favorite, we’ll add it here. Sparkfun has one, and a matching Cadsoft Eagle part library.

Power supply

An adjustable LM317 voltage regulator (IC3) is set to 3.3volts using a 390ohm (R6) and 240ohm (R7) resistor. We considered several 3.3volt regulators, but nothing was cheaper than a LM317 and two resistors. There’s a 0.1uF decoupling capacitor (C13,14) and a 10uF capacitor (C3,19) on both sides to help support the power hungry Ethernet transceiver. The LM317 will output 3.3volts from an input of 5 to 20volts+, but it gets really hot with greater than 9volts supply. The specified input capacitor is only rated 16volts, so consider an upgrade if you plan to use a supply greater than about 9volts.

For the first time ever, we incorporated a power jack (J1) into a design. A jack with a 2.1mm diameter internal pin seems to be the most common DC connector. We used a cheap through-hole DC power jack, like SparkFun #PRT-00119 or Mouser #163-7620-E. It mates with a plug like Mouser #1710-0721.

Circuit board

The PCB (full size placement .png) was designed in Cadsoft Eagle 5.0. Freeware versions are available for all major platforms. Renderings were done with Eagle3D, beta version. Schematic and board files are included in the project archive (ZIP).

We designed the project with large SOIC chips and 0805 surface mount (SMD) parts, but haters can rest assured that chips are available in a through-hole package. We prefer to use SMD parts because the resulting circuit boards are smaller, cheaper, and faster to produce. 0805 parts are dirt cheap, and easy to solder with a normal iron. Don’t expect this project to work on a breadboard, there’s probably too much capacitance for this circuit.

We took full advantage of the PIC’s programmable pin placement to get the simplest trace routings possible. Just four jumper wires are needed on an otherwise single-sided board.

The traces are large and clean, DIY toner transfer boards should be easy. We made our PCB using an inkjet printer transparency mask over an UV sensitive circuit board.

In addition to the final design, the project archive contains our v1 prototype design. The prototype uses a full size SD card (SCDA1A0901) and all electrolytic 10uF capacitors. We also put the RJ45 Ethernet jack on a daughterboard to better accommodate different pinouts.

Partslist

Firmware

Three firmware examples are included in the project archive [zip]. The examples compile with Microchip’s demonstration C30 compiler. Learn more about working with the PIC 24F in our previous article: Web server on a business card (part 1). MPLAB isn’t great about project portability, you may need to locate all the project files again if your path doesn’t match the ‘c:wsbc’ format that we used.

FAT12/16/32 disk library

Our first step was to get the FAT library reading from a SD card. FAT 12/16/32 are simple disk storage formats that work with PCs, MACs, digital cameras, music players, and other electronics. Here’s our favorite FAT tutorial/teardown (PDF).

Microchip’s FAT 12/16/32 library gives us simple functions for working with SD cards. The included demo application creates some files and directories to demonstrate each function. Here’s how we configured it to work on our custom hardware, you can find these changes by searching for the tag ‘HACKADAY’ in the code:

• HardwareProfile.h assigns actual PIC hardware to generic references in the code library. For the SD card this is an SPI interface, and pins for chip select and card detect. First, we deleted all the unused hardware profiles to make the code more manageable. Next, we configured the FAT library to communicate with the SD card using an SPI module (line 132). Finally, we defined the SPI pin assignments (line 152). Pin setup is shown in the table below.
  

  Pin	Port
  Chip select	B0
  SD card detect	A2
  SPI clock	B2
  SPI MOSI	B1
  SPI MISO	B3

• Demonstration.c. On line 48 we set a custom oscillator fuse configuration, as described in our PIC 24F introduction. This is also the logical place to configure pin assignments with peripheral pin select (line 63).
• FSConfig.h. This file enables various components of file system library, affecting the amount of memory and program space used. A read-only library is very small, a full write configuration is bigger. We didn’t have to make any changes for the demonstration, but this is an important file to note.

At first, the library failed to recognize our SD card. It only supports disks with a master boot record (MBR). Windows XP formats SD cards as a DOS disk: a single partition with no MBR. To verify this, open a Windows-formatted disk with a utility like HxD and inspect sector 0 of the physical disk. Byte 446 should be the location of the first MBR partition entry, but instead it’s the NTLDR executable code.

To format the disk in the ‘correct’ FAT format, use a digital camera’s format function or a utility like Panasonic’s SD card formatter. We also considered using a different FAT library that reads DOS disks, like DOSFS, or adding similar features to the Microchip firmware.

TCP/IP stack

Microchip’s free TCP/IP stack performs the convoluted configuration and networking functions needed to run a web server. You can read all about the stack in various application notes and documentation. Wikipedia is our favorite TCP/IP learning resource; we wrote our first TCP/IP stack using only Wikipedia.

Microchip’s TCP/IP stack used to be messy and confusing. Now it’s just confusing. The last few versions of have improved considerably in code clarity and structure. Here’s what we did to to configure the base TCP/IP stack example for our hardware, you can find these changes by searching for the tag ‘HACKADAY’ in the code:

• HardwareProfile.h assigns actual PIC hardware resources to generic references in the code library. We added our custom oscillator configuration (line 68), and configured the server status LED to use the LED attached to PORTB7 (line 83).  We defined the SPI interface to the ENC28J60 as follows (line 116):
  

  Pin	Port
  Reset	B8
  Chip select	B9
  SPI clock	B10
  SPI MOSI	B11
  SPI MISO	B12
  Wake on lan	B13
  Interrupt	B14

• MainDemo.c. We eliminated a bunch of unused code, and added the peripheral pin select configuration code to the InitializeBoard() function (line 332).
• TCPIPConfig.h defines the TCPIP stack components included in a compile. We’ve enabled DNS, DHCP, the IP announcer, and the ping server (line 56):

#define STACK_USE_DNS            // Domain Name Service Client
#define STACK_USE_DHCP_CLIENT    // Get DNS automagically
#define STACK_USE_ANNOUNCE       // Microchip Ethernet Device Discoverer
#define STACK_USE_ICMP_SERVER    // Enable the PING server

After loading this firmware, we’re ready to connect the server to a network for the first time. During initialization, the TCP/IP stack negotiates with the network router for an IP address using DHCP. We need to know this address to communicate with the device. If the device had a screen we could display the IP address, but instead we use the MCHPDetect.exe utility from Microchip.

When the TCP/IP stack finishes initializing, it broadcasts an announcement packet to port 30303 of all locally connected computers. MCHPDetect extracts the IP address from these packets. A new announce packet is sent on every PIC reset.

It’s also possible to read the IP address directly from memory with a debugger. The address is stored in the AppConfig.MyIPAddr variable, the .byte form follows the standard x.x.x.x IP notation.

Once we have the IP address, we can ping the server and test its responsiveness.

If ping shows high latency or malformed packets, you can use Wireshark to inspect network traffic at the byte level. Unless you’re in Germany, because it might be criminal.

Building the custom HTTP server

The custom web server looks for requested files on the SD card, and sends them with the correct content type. We used the Microchip HTTP example server v1 (HTTP.c) as a base for our FAT file server (FATHTTP.c).

Microchip’s HTTP server used a simple file system called MPFS to index web pages on an EEPROM chip. We replaced calls to MPFS functions with calls to functions in the FAT library (see the HTTPProcess and Sendfile functions in FATHTTP.c). Our changes demonstrate the concept as simply as possible, without adding confusing pointers and other handy C obfuscations. The code leaves a ton of room for improvements, have at it. File writes are disabled in the default compilation, but there’s enough program space to enable them if you want to write to the SD card (see FSConfig.h).

It’s necessary to registered our custom FATHTTP server with the rest of the TCP/IP stack. We did a search and replace for the original HTTP server components, and added calls to our new FATHTTP server as needed. That turned out to be these places:

• TCPIPConfig.h. First we inserted some definitions that enable the FATHTTP server (line 70), and added a TCP socket for the FATHTTP server (line 248).
• TCPIP.h. Next, we added FATHTTP to the list of services that require the TCP/IP stack (line 170) and then included the necessary headers (line 351).
• StackTSK.c. We added the FATHTTP server initialization (line 138) and processing (line 340) functions to the list of TCP/IP stack tasks.
• Helpers.c. We also needed to include a few helper functions for working with URLs (line 259).

At long last, it’s time to put some files on an SD card and test this thing. Make sure your files follow the 8.3 file name format. The project archive contains a sample website with a test image and zip file.

After grabbing the server’s IP address with MCHPDetect, we pointed a browser at it. The IP address entered alone will redirect the browser to index.htm, whether or not it exists. Web pages and images stored on the SD card display in the browser, but unknown binary types trigger a download prompt.

Taking it further

We see a lot of potential projects using this tiny web platform.

• Add hooks in the FATHTTP.c source for special URLs that trigger events or configure pins.
• Build a remotely accessible data logger. Use the extra pins to read sensors and log data to the SD card. Logs are retrievable from a web browser, or directly from the FAT readable SD card.
• Get remote access to an ancient serial terminal or BBS, optionally log the console output. Use two external pins as a serial port, and forward commands from the Internet using Microchip’s Telnet server and Ethernet-to-serial bridge examples.
• Your suggestions?

Next time, we’ll use the mini server to make an Internet connected, electronic indoor graffiti wall. This will be an interactive project where everyone can contribute graffiti and animations on-line.

Schematic, board, and firmware files are included in the project archive (ZIP). Use the freeware version of Cadsoft Eagle to view the schematic and PCB. The firmware is written in C, and compiled with the Microchip demonstration C30 compiler.

For years, Microchip PIC microcontrollers dominated; PIC16F84 hacks and projects are everywhere. The 8-bit 16F and 18F lines are supported by several coding environments and easy-to-build serial port programmers. Microchip’s 16-bit PIC24F is cheaper, faster, and easier to work with, but largely absent from hacks and projects.

We recently used a Microchip PIC24F microcontroller in a mini web server project, but didn’t find many introductory references to link to. In this article we’ll cover some PIC 24F basics: support circuitry and programming options. We’ll also talk about our favorite features, and how we figured them out. Our next article will outline a web server on a business card based on the PIC 24F.

The basic circuit

This is the basic support circuit (full size .png) for a PIC 24FJ64GA002. Some helpful documents are the code examples, application notes, individual datasheets, and 24F family manual.

Main system power supply

Peripherals and pins on the 24F PICs operate between 2.0 and 3.8volts. This is a big advantage over older PICs because the 24F can directly interface modern 3.3volt components like SD memory cards. Some 16F and 18F PICs will run at 3.3volts, but usually at drastically reduced speeds. As always, put a 0.1uF capacitor between each power pin and ground to decouple the chip from the power supply (C1, C2).

Core power supply

The processor core requires a separate 2.5volt supply. A built-in 2.5volt regulator can be enabled by connecting the DISVREG pin to ground, and placing a 10uF capacitor between the Vcap/VDDCORE pin and ground (C3). We’ve not experienced any problems using a 10uF low ESR electrolytic capacitor, but in the future we’ll use a tantalum capacitor as specified in the datasheet.

Speed and crystal

PIC 24Fs have a max clock speed of 32MHz, and complete one operation every 2 clock cycles for a top speed of 16 million instructions per second (MIPS). Most 24Fs have an internal 8MHz oscillator, but you can also use an external crystal for a more precise timebase. An internal phase lock loop (PLL) can multiply any clock signal by four.

We used a common option: 8MHz internal oscillator multiplied by four (32MHz), with full IO functions on the external oscillator pins. The clock mode is set with CONFIG2. Use these settings to run a PIC 24F at 32MHz using the internal oscillator and PLL:

// Internal FRC OSC with 4x PLL @ 32MHz
//from p24FJ64GA002.h:
//FNOSC_FRCPLL - internal oscillator
//OSCIOFNC_ON  - enable the oscillator pins as IO
//POSCMOD_NONE - Primary (external) oscillator disabled

_CONFIG2(FNOSC_FRCPLL & OSCIOFNC_ON &POSCMOD_NONE)

Programming connections

Microchip’s standard 5 wire in circuit serial programming (ICSP) connection is used to program the 24F. ICSP consists of a clock line (PGC), bi-directional data line (PGD), master clear and reset (MCLR), and connections to power (V+) and ground (GND).

The MCLR function resets the chip when voltage levels are too low to operate. Enable it with a 2000 (2K) ohm resistor (R12) from the system power supply to the MCLR pin. Optionally, add a button (S1) from MCLR to ground for a manual reset switch. The programmer also connects to the MCLR pin to reset the PIC and control programming modes.

PIC 24Fs have several sets of programming pins labeled PGDx and PGCx. Choose the set most convenient for your design. One catch: you can’t use the clock pin of one set and the data pin of another, you have to use the same pair.

The primary pin pair used for debugging is programmed in CONFIG1 with the ICS_PGX option. This only effects debugging; programming is still possible from any pin pair.

_CONFIG1( ICS_PGx3)

Coding and Programming

Unfortunately, the 24F can’t be programmed with the hobbyist-favorite serial port programmers. These are usually 5volt programmers that place 13volts on the MCLR pin. 24F PICs are rated for 3.8volts maximum on the MCLR and programming pins, old serial port programmers will destroy them.

The ICD2 is Microchip’s cheapest programmer for the full 24F line. An education discount is available if you have a .edu email. There are numerous clones too, most notable is the Olimex PIC-ICD2 clone, also sold by Sparkfun. We’ve never used it, but it’s supposed to be an exact clone. You can also try your hand at building a DIY ICD2 clone, we’ve had luck with the PiCS Rev B in the past. You’ll probably need to build an adapter to use a homebrew ICD2 with a PIC 24F.

MPLAB is a free development environment for coding, compiling, and debugging all PIC microcontrollers. We like to program in C, so we downloaded the free, evaluation/student edition of the Microchip C30 compiler that integrates into MPLAB. HI-TECH’s C compiler is a fairly popular alternative if you’re not thrilled about MPLAB.

Microchip’s low-voltage 18FxxJ line, such as the Ethernet enabled 18F97J60, can only be programmed a few hundred times. That’s fine for production, but really unfriendly to a developer. We’re exceedingly happy to note that the 24F can be programmed at least 10,000 times.

New features and improvements

We made a list of the things we liked best about the PIC 24F after using it in a project. Not all of them are new, sometimes little improvements make designs much simpler.

8-bit vs 16-bit

C programmers won’t notice many differences between 8-bit and 16-bit architectures. Native 16-bit math operations will save you a few cycles if you do 16-bit integer math. Memory and registers are 16-bits long, meaning the default 16-bit variable type counts to 65,536, rather than 255.

Peripheral pin select

Peripheral pin select (PPS) is our favorite feature on the PIC 24F. The digital peripherals SPI, UARTs, timers, etc can be connected to almost any pin on the chip.

PCB designs get really creative because the pin arrangement on a microcontroller rarely matches that on the peripheral you’re interfacing. Compare these two designs. The design on the left uses looping, winding traces to connect a SD card without jumper wires. On the right, we used PPS to assign pins in a way that lined up perfectly with the SD card. We spent caffeine fueled nights routing the board on the left, but only hours on the other. We’ll find it difficult to ever work with a PIC 16F or 18F again because of the complete and total awesomeness of PPS.

Input and output pins are assigned differently: pins are assigned to inputs, outputs are assigned to pins. A peripheral input, such as the “serial data input” (SDI) signal of an SPI interface, is set by putting a pin number in its register. In the C30 compiler, SDI of SPI1 and SPI2 are assigned like this:

// Inputs
//SDI1 B12/23/RP12
//SDI2 B1/5/RP1

RPINR20bits.SDI1R = 12;            //SDI1 = PORTB12

RPINR22bits.SDI2R = 1;            //SDI2 = PORTB1

Output functions are handled in the opposite way. A group of registers represent the programmable pins (RPORx). Peripheral outputs are assigned to each pin. Assign the SPI “serial data output” and “clock output” lines like this:

// Outputs
//SDO1 B11/22/RP11   //CLK1 B10/21/RD10

RPOR5bits.RP10R = SCK1OUT_IO;     //RP10 = SCK1

RPOR5bits.RP11R = SDO1_IO;        //RP11 = SDO1

//SDO2 B3/7/RP3       //CLK2 B2/6/RP2

RPOR1bits.RP2R = SCK2OUT_IO;     //RP2 = SCK2

RPOR1bits.RP3R = SDO2_IO;        //RP3 = SDO2

Check the device datasheet and the IO with PPS datasheet (PDF) for a complete list of peripheral (RPINRxx) and pin (RPORx) registers.

Individually configurable pull-up/pull-down resistors

Pull-up and pull-down resistors hold inputs at a known level when there’s no other signal. Illustrated below on the left (S1), a pull-up resistor (R1) normally holds the signal high (1). A button press pulls the signal to ground (0). Without a pull-up resistor, the value on the microcontroller pin will fluctuate wildly (state undefined) until a button press pulls it to ground (0).

Internal pull-up resistors make it easier to route a button on a circuit board. An internal resistor holds the signal high until the button pulls it low, saving a resistor and power supply trace (S2). PIC 16Fs and 18Fs sometimes have an all-or-nothing pull-up on 8 pins, but the 24F adds individually configurable pull-up resistors. See the IO datasheet (PDF).

CRC hardware module

Cyclic redundancy check (CRC) values are used to verify the integrity of data. Your PC calculated CRCs for the TCP packets that carried this page over the web. The 24F has a hardware CRC module that does tedious CRC calculation without processor involvement. Check out the datasheet (PDF) and example code (ZIP).

Real time clock and calender

Microchip added a hardware real time clock and calendar module (RTCC) to every 24F. It’s always been easy to add an interrupt-based clock to a microcontroller, but this module takes care of everything without timing concerns.

The RTCC module requires a 32.768khz watch crystal (Q1) to be connected to the SOSCx pin pair. Don’t forget 2 suitable capacitors for your crystal, we used 27pF (C1,C2). There’s a datasheet for the RTCC module (PDF), and example code (ZIP).

Package sizes

Microchip continues their tradition of offering products in a range of package sizes. Low pin count parts are available in through-hole (DIP) and several surface mount sizes. As with all manufacturers, though, the largest, coolest, chips are only produced in surface mount packages. Microchip is a fan of 64, 80, and 100 pin thin quad flat packs (TQFP), a square chip with an equal number of pins on all sides. TQFP isn’t terribly difficult to solder, but the circuit boards can be a pain to make at home.

Conclusion

The past was dominated by 8-bit PIC 16F and 18F-based microcontroller projects. 16-bit PICs, however, have been largely neglected. If you’re already considering a PIC for your next project, check out the 24F series. The peripheral pin select feature alone is worth the switch — it simplifies circuit boards, reduces routing time, and saves board space. We were able to fit an entire PIC 24F web server on a business card using a home-etched PCB. Our next article will introduce this simple server prototype.

The project archive (ZIP) contains the base schematic for the PIC24FJ64GA002, and a custom 28pin part we added to an existing PIC 24F part library. Both are for use with Cadsoft Eagle, a freeware version is available for most popular platforms.

In most settings business cards are given out without much thought. But what if you could make your card stand out from the rest? By using a 5×15 LED matrix screen, a single micro controller, a number of resistors, switches, and other parts, [tomward] has put together one very slick business card that’s sure to draw attention.

The included instructions go into great detail on the construction, but [tomward]admits that you will need some knowledge in electronics in order to build one yourself.  After reading the instructions ourselves we would have to agree with him.

If you’re into programing micro controllers and are handy with a soldering iron you may want to give this a shot.