MC9S12DP256 Microcontroller Development Board

Introduction

This is a development board I designed based on the Freescale MC9S12DP256 or MC9S12DP512 micro.

Features

• MC9S12DP256 Features: 12K bytes RAM, 256K bytes FLASH, EEPROM, Dual Async Serial, 3 SPI serial, 5 CANBus ports, 8 channel PWM, 8 timer counters, 16 channel 10 bit A/D etc, HCS12 instruction set.
• The pin compatable MC9S12DP512 chip, with more memory, can also be used.
• 60 I/O pins organized as 5 connectors with identical 12 bit (8 bits plus handshake) pinouts. All of the I/O lines are availible for user use without conflict with onboard peripherals (one exception noted below).
• 16 analog inputs on 2 connectors with similar pinout to the digital connectors. Unused analog inputs can be used as digital inputs.
• 8 channel SPI DAC (D/A converter). Pinout compatible with analog inputs.
• BDM In port. Supports Background Debug mode with an innexpensive BDM pod instead of an expensive In Circuit Emulator.
• BDM Out port. The micro board, when flashed with Freescales's D-BUG software, can function as a BDM pod. Note: due to the requirements of the D-BUG software's BDM, this does steal two I/O pins from one of the standard I/O ports.
• Very few pins are essential for the core to work (power, clock, RS-232, rest). Any shorts or opens on other pins can be diagnosed using the pintest application. This makes the board a good candidate for those who don't have much experience with surface mount assembly.
• 16Mhz crystal oscillator. On chip clock multiplier can boost this to 48Mhz.
• RS-232 Serial Port
• 5V regulator onboard works with 8-12V input.
• Reset button
• Compatible with Freescale's D-BUG12 debugger in either native mode or BDM Pod mode. Normally, D-BUG12 requires that you give up two analog inputs for mode select jumpers but an analog multiplexor is included that lets you switch those pins back to analog inputs.
• FPGA migration path (see below).
• The PCB layout was carefully crafted to provide good power and ground quality even on a Two layer board. This board was designed to be fabricated with either a two layer or four layer board. So far, there is no indication that a four layer board would be beneficial. The two layer design facilitates embedding this board in a larger board with application specific circuitry. Around 75% of the bottom of the board is ground plane, with bridges on the top layer where the ground plane is interrupted.
• I/O pins are on the board edge side of the connectors. It would have been easier to layout the board with the ground pins on the outside edge. The I/O pins on the edge facilitate making peripheral modules using even home/lab etched single sided boards, because those modules can take the shortcut of putting the ground pins on the board edge. The I/O pin location also facilitates embedding in a larger design, either as a daughter board or by cutting and pasting the micro design into the application board. It also facilitates using breadboarded I/O modules.
• Facillitates Three stage prototyping. First stage is to use the micro with peripheral I/O modules. Second stage is to make an application board with connectors that the micro can be plugged into as a daughterboard (application board doesn't necessarily require surface mount capability). Third stage is to cut and paste the micro board into the application design.
• All components are availible from a single vendor (Digikey).
• Passes DFM tests and meets standard low price prototyping design rules at some commonly use PCB shops.

Avoids common pitfalls of Micro Development Boards

• Half the I/O pins used up with onboard features.
• Haphazard I/O pinouts. Pinouts do not match up from one I/O connector to another.
• Pins not programable as input or output on a per pin basis.
• On some newer micros, I/Os are not 5V capable.
• Insufficient grounds on I/O connectors.
• I/O connections on funny connector and not usable in lab without a separate breakout board.

Sensible Pinout

One of the nicest features of this board is the sensible pinout of the I/O connectors. All the I/O pins are fully functional I/O, individually programmable in each direction, though some have additonal special functions.

The 12 bit (8 bits + 4 handshake) can be used in a wide variety of ways:

• 12 bit general purpose I/O
• 4 bit SPI plus 8 additinonal chip selects
• 4 bit SPI plus 8 bit address
• 4 bit SPI with 256 possible chip select sent while CS is not asserted, plus 8 additional I/O pins
• Three separate SPI ports. Three separate 2x4 pin C-grid/Amp-modu connectors can mate with each I/O connector.
• 12 separate switch inputs or LED outputs, using 2 pin C-grid/Amp-modu connectors (there is a ground next to each signal
• 12 separate 1 bit ports (with ground), 6 separate 2 bit ports, 4 separate 3 bit ports, 3 separate 4 bit ports, 2 separate 6 bit ports, or various combinations using Molex C-grid or Amp Modu crip contacts and housings. These connectors fit together side by side so you can make up reusable standard cables rather than needing to make up a single use adapter cable.
• A port, or portion there of, can be used with standard 2 pin shunt jumpers (and internal pullups) as a jumper configuration port to select software modes.
• Multiplexed address/data bus. 8 data, 1 read strobe, 1 write strobe and 1 Address strobe.
• Same as above but with 16 or 32 bit addresses sent by multiple clocks on the strobe line.
• Two ports can be combined to provide a non-multiplexed 8 bit data + 8 bit address bus (with additional control signals), or 8 bits data + 16 bit address (low byte multiplexed).
• Two ports can be combined to provide a 16 bit data + 16 bit address multiplexed bus.
• Parallel printer interface
• Two ports for an IDE interface
• Single port IDE interface with external CPLD
• 8 bit bidirectional bus: 8 data, direction, strobe, bus/service request, 1 bit begining/end of packet.
• Two connectors can be connected together with a standard ribbon cable for loopback test. This includes the analog in and analog out connectors which can be connected to each other or to a digital connector.
• USB Fifo interface (FTDI)

Using ribbon cable connectors or stacking male/female connectors and one of the SPI with chip select or parallel with multiplexed address formats, multiple boards can be connected to the same 12 bit connector in many applications.

Additional modes which would be more usable with a more powerful micro (FPGA based) and/or a CPLD enabled peripheral.

• Nibble buses in each direction between two micros. With double pumping, 8 bits can be transmitted on each clock cycle.
• High speed parallel D/A and A/D interfaces for video, oscilloscope, and other applications.
• Double pumped 16 bit datapath.
• Ethernet, USB, etc. Physical Interface (PHY) connections.
• interface to SERDES (typically one port each direction). PCI-Express, SATA, Firewire, DVI

I thought about using a smaller connector, but no other connector series is as versatile in the lab. 26 pin header connectors are availble in standard IDC ribbon cable, 26 cavity housing + crimp contacts (Molex C-grid or Amp-Modu), 26 contact discrete wire termination IDC connectors, Male/Female board stacking headers, PCB mount straight or right angle male or female connectors (through hole or surface mount), Board to board standoff connectors, Connectors are availible in tin or gold. Mates with standard breadboard patterns. 26 pin ribbon cables with header to DB25 connector or DIP headers or edge connectors are standard items. Smaller pin count housings and crimp pins (C-grid/Amp-modu) can be used to connect a subset of the pins. Some of the more useful sizes: 1x1, 1x2, 2x2, 3x2, 4x2, 8x2, 6x2, 1x4, 1x8, 1x12. Header pins mates with standard logic analyser leads (just pull off the clip). A wire with a crimp pin on each end protected by either a 1x1 housing or heat shrink tubing is a very versatile jumper. Test point access adapters are availible off the shelf or can be fashioned with a piece of protoboard or a ribbon cable with an extra IDC connector and a male header. Inline switch isolation adapters (to disconnect individual pins) are availible off the shelf. Ribbon cables from IDC connectors can be ripped to individual leads (get the rainbow wire - it rips better and is easier to trace) or to subsets (I.E. rip one 12 bit interface into three 4 bit interfaces). IDC ribbon cable direct to board solder connectors are availible in the same pinout. Flat flex cable assemblies with header connectors in various sizes are readily availible (but they tend not to stack end to end). And break to length strips are availible. And almost any lab has some mating connectors laying around.

Software

By the Author

• A test application I wrote is availible. It includes a boundary scan to check for shorted/open I/O pins. It also has commands to query or set the level on any pin. It supports analog input and output.
• Drivers for many onchip peripherals including Async serial, SPI master, A/D converter, D/A converter,
• Fast Srecord downloader and converter. Works in native or BDM mode. Even works with USB to Serial port adapters which have flow control problems. Downloads a 213K program in about 1 minute 18 seconds, compared to 45 minutes with NoICE12 or one hour with Hyperterm using a USB Serial Adapter. Translates the addresses produced by the GCC toolchain into a form that is compatible with Freescale's D-BUG12. Runs on Linux (and compatible OSes) and on Windows under Cygwin.

Third Party Software

• Freescale's D-BUG12 debugger can be used. Note that D-BUG12 can't program the flash in native mode, because you can't run the debugger from flash while writing to the flash, but you can store code in RAM and EEPROM. However, my flash utility has a mode where it downloads a flash programming routine into RAM to permit programming flash.
• GCC HC11 - C compiler (free, open source)
• GDB HC11 - Source Level Debugger (free, open source)
• GAS HC11 - Assembler (free, open source)
• Objdump HC11 - Object File dumper/disassembler (free, open source)

Files

• Gerber Files: FEL9S12DP256_R1.00.zip
• layout.pdf
• layout.ps
• micro.pcb (pcb)
• micro.sch (gschem)
• schematic.pdf
• schematic.ps
• micro_bom.csv (In Digikey upload format).

Surface Mount

This board uses surface mount components except for most of the connectors. This includes two high density 0.65mm (0.025") lead parts, the micro and the D/A converter. It is feasable to assemble this board in a home or throughole lab, however. And the pintest application makes it easier to debug any mistakes. You will need at a minimum, a fine tip temperature controlled soldering iron ($50), fine guage solder, fine tiped tweezers, a sharp pick, and solder wick. A syringe with flux is also nice to have. A syringe of solder paste can also be used. A bright light and hands free magnification is essential. If you can see it, you can probably solder it. Options include a binocular microscope, a swing arm illuminated magnifier ($75), or a visor magnifier ($30 - I used one with two different lens pairs and installed both (the second one held on with a wire tie) for additional magnification. The binocular microscope is best for the 0.65mm parts, but it can be done using the magnifier lamp or with the visor and the magnifying lamp used simultaneously. A hyperdermic needle (standardsharp, not blunt tip) is good for scraping between leads to remove solder bridges.

Howard Electronics is a good source for the equipment. The Microscope Store has stereo and trinocular boom microscopes for under $600. Pay attention to the focus distance specs, you want enough room under the microscope to work. A trinocular scope lets you attach a camera without removing one of the eyepieces. A good digital camera that will focus up close can also be used for inspection.

License

Free for personal use. Contact me for commercial licensing, such as to sell boards or to embed the design in a larger board.

Daughterboard Expansion connector

Additional expansion connector (unused). Provides SPI with multiple chip selects, both async serial ports, additional input and output pins (SPI based). Additionally, some analog inputs (intended for 2 joysticks) are availible on this pin (via an analog mux to the main analog inputs).

This connector was originally intended for a user-interface daughterboard that would have 2 opto-isolated RS-232/RS-422/RS-485 switchable serial ports, optoisolated canbus, LCD display, 2 joysticks, 16key keypad, 4 pushbuttons, 3 LEDs, touchscreen interface, SD/SDIO/MMC card interface, real time clock, and LEDs. It uses a smaller 50 pin 0.5mm flat flex connector.

Erratta

This board was designed under horrendous time pressures, and this was the first prototype pass. I.E. this was my "breadboard". With wire mods, the board has stood up to over a year of testing.

A few wire mods were required to circumvent limitations of a couple pins on the micro.

• Capacitor C29 is backwards on schematic and PCB. C29 should point the opposite direction from its neighbors.
• Values of capacitors C15 and C17 were swapped. C15 should ] be the zeroohm.
• C17 side of XTAL needs to be grounded Run a jumper to the nearby side of C10
• pins MODA, MODB, IRQ, and XIRQ are used as I/O but are input only.

• connect X01-1 (right) to C10-2 (top)
• Connect U04 pin 21 to U03 pin 1
• connect U04 pin 19 to U03 pin 2
• cut traces from U04 pin 37 and pin 38. Note that it is safer to do this about 3/4" from the chip. Connect both of these pins to ground (pin 40).
• Two pins on TL431A are reversed. Easiest to fix with a TO-92 package part but the surface mount part can be rotated 180 degrees and offset.
• U10 pin 19 to U06 pin 8

Some of these changes may be relected on the schematic and/or PCB but I think I was interrupted before I finished.

User interface board (vaporware)

The user interface board connector pinout isn't very rational. It is the result of taking a schematic for a single board and dividing it into two boards by dropping a pair of connectors in the middle. I decided that two double sided boards back to back made more sense than 1 4 layer board with components both sides for few reasons: in small quantities, cost was about the same (after all a 4 layer board is basically 2 two layer boards laminated together), I needed the first board immediately for a project but the second could wait, and for applications that didn't need all the extra features why pay for the second board.

I am not planning on building the user interface board that mates with the flat flex connector anytime soon, unless I have specific client requirements. Already have schematic and parts placement, but not routing. Some of the functions will show up on separate peripheral modules. I may produce a similar user interface board, but I will be moving away from the flat flex connector and using a standard 12 pin interface. I might make an adapter allowing the flat flex connector to be used to avoid tying up any of the user I/O ports.

Future Plans

I am focusing my development efforts towards FPGA embedded and FPGA attached micros. They will use the same connector pinout but not necessarily the same footprint. They will support 5V TTL/HCT level, 3.3V, 2.5V, and possibly 1.8V, and 1.2V signal levels. Probably 72 I/O pins on 6 connectors. A/D and D/A will likely be a separate board. Many megabytes of RAM and MMC card flash. JTAG. Option to run embedded Linux.

As an intermediate step, I plan to make an adapter from the Xilinx spartan3e development board FX2 connector to three 12 bit I/O connectors.

I have sketched out a whole bunch of I/O boards that will use the standard 12 bit ports (or subsets). RS-232/RS-422/RS-485, LED indicator boards, switch input boards, LCD display, relay driver, motor driver, ethernet, USB, RS-422 driver/receivers for non-communications applications, level translation, SPI A/D and D/A, high speed A/D and D/A, FTDI USB, etc.

The current micro doesn't support differential (LVDS) signalling but futur ones will. The 26 pin connector was designed with two options for differential signals. One is to use two adjacent data pins as a differential pair. The other is to replace the signal return lead (gnd) with the negative differential signal.