FMVSS138 Tire Pressure Monitoring System

I was scanning the web yesterday and I came across a new vehicle interface, or maybe a vehicle system. The new interface is called the Tire Pressure Monitoring System or TPMS. The TPMS standard requires cars and trucks to have an early warning system to alert the driver that one or more tires on the vehicle is below their rated tire pressure. The standard went into effect around 2006, but this was the first I ever heard of it. I drive a 2006 Ford Mustang but I don't remember ever seeing it light, so it didn't make it to my model year.

The links pointing to the page include a 'T' Buses page, Electrical Interface Buses page the Engineering Acronyms page and the Definition of Torque page [first term on the page].

So we get another idiot light on our dash-board. However the TPMS light shows a tire to indicate a 'flat' instead of the engine-symbol light used by OBDII which nobody could ever figure out [check engine]. Now TPMS really indicates low tire pressure and not a flat, but one of the possible symbols appears to be a flat tire

Now it's not really an electrical bus, but it could be an electrical interface so that's why I listed it. I also added the spec to the web site so I wouldn't have to try and figure out what it was a few years from now. Apparently this standard does not really depend on any defined electrical or physical interface, it just has to perform its function.

Avionics Buses

I added a new page today to cover the PI-Bus. The PI-Bus was already listed on the site but only in passing because I really didn't have much data. I still haven't added much to the page, but it's more than I had before and a bit much to leave on the Avionics Data Buses page. I also added a new link to PI-Bus off the interface buses page 'P', data had already been listed there.

Even though I only added a few sentences more than the site already listed, it took 3 hours. As I uncovered data that needed to be added to related pages, so several pages were updated just because of the PI-Bus update. Oh and because I always start with a copy of another page to begin a new page; I updated and used the AFDX page to begin with.

Last week a page covering Laser Diode Manufacturers was added, but I never got around to adding the addition here. The search engines have already found that page but I mention it regardless. That page was linked of each of the other four Diode pages.

Graphic; F-22 Raptor, open source. The F-22 uses the PI-Bus.

Manufacturers, Bus Definitions and pinouts

A few new pages have been added over the last few weeks. Today I added a page to cover Manufacturers of Laser Diodes. I also added a link to a number of pages including Diode manufacturers, Zener Diode Manufacturers, and Companies that produce Varactor Diodes. The page only contains three manufacturers, but I'll get it updated in the next few days.

Last night I added a page to cover PS3 connectors, not sure why but it is an electrical interface. Looks like one of the pins may contain an error, but I added a note to indicate that. The new PS3 page is linked off this bus page; Interface Buses, 'P'.

Last week I split up one of the Printed Wiring Board Terms page, but I don't remember which one;
PWB Terms, A - O.
PWB Terms, P - R.
PWB Terms, S.
PWB Terms, T - Z.
Of course many pages have been updated, but only new pages get listed here.

How did the OBD vehicle Interface come about

I'm not sure why but I added a page to cover the Background of the OBD bus. OBD stands for OnBoard Diagnostics and is used as an in-vehicle debug port. I guess I added it because I was up-dating a few OBD pages and got a little interested in the history.

Although reformatted much of the data is from the EPA's site [EPA sets the standard requirements], with some supporting data from a few state government sites..

The OBD interface makes that 'Service Engine Soon' light to come on in your car, the light that no one knows what it means.

I linked the new OBD page off the OBD Terms page. The main page relating to OBD is the Description of OBD listing.

Graphic; Dash Board Check Engine Light.

What are Serial Buses

Well a serial bus is a bus with a single data line, or a pair of data lines in the case of a differential set. How come PCI express uses a pair of receive lines and a pair of transmit lines, I guess you could say it's still a serial bus but with simultaneous transmit and receive capability. But what about the JTAG and SMbus interfaces that get glued onto the PC expansion bus? Is it still a serial interface. The 1x PCIe bus uses 36 lines, including power and grounds, that's a lot of pins for a serial bus.

Now what about the 16x PCIe interface? PCIe 16x has 16 differential pairs going in each direction [16 Tx and 16 Rx], and it still has the JTAG and SMbus interfaces. That's 164 traces for PCIe once you count all the ground lines. At least some serial buses like CanBus use one net [pair], or a differential pair but it still requires a 9-pin D-sub connector.

How is that different from an 8-bit, 16-bit, 32-bit or 64-bit parallel bus? The PCI bus only uses 188 pins to develop a 64-bit bus, that's only 20 more nets than PCIe and you get a lot more control pins.

So you get your requirement to interface two boards together and your told that one of the boards is I/O constrained, do you walk into a design review and say you serial bus implementation requires 164 nets?

The first digital bus I ever designed to was the GPIB interface, the old byte serial, bit parallel interface. So I really already know what the difference between a serial bus and parallel bus is; A Serial bus transmits a byte sequentially one bit at a time, while a parallel bus sends the entire byte out at once over individual lines. There is no limitation on the number of pins for a serial bus, but I would assume the normal assumption would be less than a dozen nets at most.

The point is a new page was added covering the Serial Wire Debug Interface, one of the true serial buses. Well maybe not, looks like it needs power and ground and resides on a ten pin header. Maybe IC to IC communication on the same PCB only requires just two nets, I'll have to do a bit more research on the topic.

Of course any copper wire parallel bus will be lighter weight than a hydraulic control system. With less lines, a serial bus should be lighter still, requiring less wires than a parallel interface. Better yet a network designed to operate over an Optical fiber would come with the lowest weight penalty.
With the cost of putting metal into space being about $10,000/pound the best design would be the safest, most reliably and the lowest weight. The same is true for any Avionic Bus Design. The Protocol may not set the maximum weight of the bus but an interface's protocol sets the minimum safety requirements of an interface and monitors and adds to a buses reliably.


Graphic; Comparison of different size NASA rockets: Saturn V, Space Shuttle, Ares I, Ares IV, and Ares V.

Interest in the PCI Bus is Falling

I was just updating some of the data relating to the PCI Bus yesterday, really just adding some data. There was no new page added.

The main page relating to the Peripheral Component Interface is the PCI Bus Description. Just a few lines of text were added, the real update occurred on the page containing the PCI pin out,[which does not have a page rank?]. I started to add a better description of the signals, and added a few more notes. There are also two additional pages that were updated, each related to PCI card size; Half Sized PCI Board, and Full Sized PCI Board. I guess the only other page is Manufacturers of PCI Boards, but it wasn't updated.

I noted a steep decline in page visits for any of the pages relating to the PCI Interface, by about 4-to-1 over the last three years. Google had data that goes back to 2004, so I posted their graph for PCI Bus searches instead.
The Graph is a Google Trend for the search term PCI Bus.

Sony's DMP Interface

I added a new page the other day to cover the Digital Media Port [DMP] interface. The bus was developed by Sony and only resides on their gear. The page lists one possible pin out, and I don't know if there may be others. I have no other information on the interface.

Digital Media Port

The page is linked from these two pages;
Engineering Interface Buses, 'D'.
Cable and Backplane Buses.

Because this bus is only being used by Sony I may not be able to find any additional data.

NATO Interface Bus

A new page was added that covers NATO Advanced Data Storage Interface [NADSI], or STANAG4575. The specification details a board used for removable memory. The electrical interface used Fiber Channel, but one of the possible physical interfaces is a 50-pin D connector. The D-connector must be used for legacy systems, seems a bit odd. Also it uses the out-dated MIL-DTL-24308 series connectors. It seems under normal conditions the interface will be on a MIL-DTL-38999, which makes a little more sense.

Any way for the NATO name, I added a link from the 'N' interface Buses, and for the STANAG name a link was added from the 'S' interface buses page.



Photo credit; Army ".. memorial for three Soldiers from the 252nd Combined Arms Battalion, 30th Heavy Brigade Combat Team ..."

Nexus 5001 embedded processor debug interface

The Nexus 5001 specification, called the Standard for a Global Embedded Processor
Debug Interface was released by the IEEE in 2003 as IEEE-ISTO 5001.

I added a page to cover the topic on the 6th of January as Nexus 5001 Interface.
I wanted to update the page just now but could not remember the page title. I did a Google search, but nothing showed up, and I paged around with out it finding either.

Looks like I linked to the text off the Design for Test page, which has not yet been spidered by Google yet. I just added another link off the alphabetic listing of buses page, Interface Buses 'N'. The Nexus 5001 standard calls out a connector but I'm not yet sure if it's a 'Cable Bus' or add-on board, 'Mezzanine Bus', guess I need to read the spec. However it definitely is a debug specification that uses the JTAG interface.

I went ahead and added a link to the new page off the Bus Design page, which lists all most all possible interface standards listed on the web site.

Adding this posting will insure that the page covering the Nexus 5001 standard will be spidered now. But it still may be a few days before the topic is indexed on Google or that it shows up on a site search within interfacebus.com. It must be time to generate and up-load a new sitemap to Google, and to update the page to add additional information of the subject.

I did just add yet another new page that provides manufacturing part numbers for Nexus 5001 connectors, Nexus 5001 connector manufacturers. Not really sure how long that page will reside on the web site, part numbers do tend to change. The vendor page has no out-going links, so maybe it's ok to leave it.....

Mini DisplayPort Specification

Apple Computer released the Mini DisplayPort standard in October of 2008. The new standard is very similar to the DispalyPort specification that was released by VESA in 2007. The new standard is controlled by Apple and differs from the original DisplayPort standard in a number of way, including a smaller connector and a different pinout.

Currently only the DisplayPort page links to the Mini DisplayPort page. With the link missing from the Video Monitor Buses page, the PC Interfaces Bus page, and a number of other computer bus related pages.

Only Apple uses the Mini DisplayPort interface....

Automotive Buses

A new page was added off the main Automotive Bus description page to cover the Mazda Engine Control System. I get the impression that the Mazda Engine Control bus was used up until the mid 1990's when it was replaced by the Electronic Engine Control [EEC] interface. The system was used with engines produced by Mazda and with Ford cars that used Mazda engines.

Can't find much data out on the web, so there are only a few words on the topic.

M-Module Mezzanine Cards

Added a new page to cover manufacturers of M-Module mezzanine cards. The new page supports the existing page which held the M-Module description. A link to the new page was added to each of Mezzanine Card Manufacturers pages.

As time permits manufacturers which also produce MA-Module boards will also be added to the page.

The site contains two main pages with links to OEM board manufactures links:
COTS Card Manufacturers,
Industrial Board Formats and Manufacturers.

COTS = Commercial Off The Shelf
OEM = Original Equipment Manufacture

OBD II Vehicle Cable Assemblies

The On-Board Diagnostics II [OBD II] interface is a vehcile interface required on all cars and trucks in the US after 1996. Refer to the main page for a short description of the OBD II interface. The signal assignments for OBD II is listed on the OBDII pinout page. However this pin out is for the OBD II end of the cable and not the far end which may be a DB9, or DB15 as shown below. The graphic to the left shows a OBD II female to OBD II male cable assembly, click for a larger image.

The new page additions hold pictures of different types of OBD II cable assemblies. An OBD II connector is always on one end of the cable, with some other connector style on the other end. In most cases the far end of the cable is either a DB9 or DB15 pin connector.

OBD II Cable assemblies; OBD end listed first.

Male narrow OBDII to DB15 pin Cable.

Female OBDII to 2x2 pin Cable. Split, VW

Right Angle Male OBDII to female DB-9pin Cable.

Male OBDII to DB9-pin Cable right angle.

Male OBDII to Male DB9-pin Cable.

Male OBDII to Male DB15-pin Cable.

Male OBDII to Female OBDII Cable. Gender changer

Female OBDII Cable to BMW connector. Circular, BMW

Each of these pages have links to all the other cable pictures, assuming no broken links..

Link to description of many other Automotive Buses.

The new cable assembly pages have not yet been added to sitemap for interfacebus.

OBD II Cable Assemblies

The web site contained three pages which referenced the OBD vehicle interface. The main OBD description page, the OBD pinout page, and a Glossary page for OBD terms. It appears that the OBD pinout page [signal assingments] is identical to the main page.

Both of those pages were pointing to graphic [gif] files to detail OBD II cable assemblies. Now those gif files are moving to their own pages, looks like tonight the correct links will reside off the OBD pin-out page. The main OBD bus page will be up-dated some time later.

Looks like there are 4 of 7 pages generated tonight;
OBDII to DB15 pin Cable assembly,
Narrow OBDII female connector to VW 2x2 connector Cable assembly,
Right Angle OBDII to DB9 pin Cable assembly,
OBDII to Right Angle DB9-pin Cable assembly.

Because all the pages contain links to all the other pages, they all need to be checked to insure that they all have the correct new links. So not all pages contain the correct link 'yet', as some have not been generated when another page had not been generated. It's a copy/paste error.

The OBD [On-Board Diagnostic] interface is used in cars and trucks to check engine status. The new pages show different cable assemblies, but pin outs are coming. The new links are under the OBDII Cable Assemblies heading per the pages refered.

PXI Express

The new Personal Computer video interface bus, PCI Express has been out for a few years now. The PCIe interface replaced the AGP bus which was used as a high speed video expansion slot shipped in PCs. As a video bus PCIe used a number of redundant lanes, or 16x to archive its high speed throughput. Because of its 2.5Gbps transfer speed (1x) the interface also started to replace the aging PCI bus, used for all other expansion slot functions.

Any way the PCIe bus started to replace all the other embedded buses based on the PCI interface. The upgrade path for cPCI becomes cPCI Express, PCMCIA went to ExpressCard, MiniPCI becomes Mini PCI Express, and so on.

Because many of the upgrades use the same physical interface, board format and function, but only change the electrical interface, page additions have been slow. Of course it takes a year or so before the interface is adopted by OEMs too.

A number of years ago the VME interface bus migrated to an instrumentation bus called VXI, low noise ~ high rel. Compact PCI [cPCI] did the same thing with the PXI interface [Compact PCI for Instrumentation]. PXI continued the advancement moving to PXI Express, using PCIe as the electrical interface and dropping the PCI bus.

So, four new pages were added to the web site today relating to PXIe;
System Slot pin out, PXI Express.
System Timing Slot, PXI Express.
Peripheral Slot pin out, PXI Express.
Hybrid Peripheral Slot pin out, PXI Express.

The pages link off the main PXIe page and have a listing in the html -- but because of those additions the pages do not yet contain the pinout data. Like all new pages, I add the page before the data gets loaded. A number of pages relating to the embedded PCIe interface have been updated.

PXI Express uses the same card form factor as PXI and cPCI, and some VME board sizes.

GPIB Connector Diagrams, Mechanical Drawings

Several pages have been added to hold military CID [Commercial Interface Document] paper mechanical drawings for the IEEE-488 connector, GPIB [General Purpose Interface Connector].

The main link is off the top level HPIB Description page, to IEEE488 CID Mechanical Drawings. Here are the new pages, that carry the CID drawings:
A-A-55094,
A-A-55138,
A-A-55139,
A-A-55140,
A-A-55141,
A-A-55144,
A-A-55145,
A-A-55146.

These page show the mechanical drawing for the connector, and provide no other data other than the specification title. The purpose of the page is to hold the connector picture or gif and that's it.
The page addition to the site map is coming soon.

What is the Minimum Serial Bus Lenght

The minimum distance for the next closest bus node [in a serial bus] is determined by the length of the wire and the signal reflection time. A quick link for minimum Node length, or keep reading the blog ...... but give me a day. The link is off the RS485 page [EIA485].

The maximum bus distance is almost always provided or can be determined, but you never see the minimum distance. And I never noticed......

Vehicle Buses

Added the OBDII pinout to a new page. The link is found on the main OBDII page. The OBD [On-Board Diagnostics] is one of a number of different Automotive Buses.

The attached picture is a US Military [Army] hybrid vehicle. Not sure when the new Humvee replacements come on line, better be soon. I Hear 70% of a convoy is taken up just carrying fuel.

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The sitemap has been viewed 650 times so far this year.

Military Specifications Resource

Some content has been removed by the editor.... The page is meant to document a number of common Mil Spec document numbers and their title. It's really just a place holder to contain the information. Put a few new graphic files up at the same time. Also linked to the the main pages for MIL resistors standards and MIL capacitor standard pages on interfacebus.com. Seems like a good start for the page....

On www.interfacebus.com, I added the GVIF description page. The GVIF [Gigabit Video InterFace] bus has been released sense 1997, but, it's news to me. Looks like a Sony only interface bus.

I added a holding page, so I should get back to it soon, I hope.

Comparing different PC Buses

The main listing of Personal Computer Bus description is listed on the Personal Computer Buses page. In addition to providing links to almost all of the different styles of PC buses the page provided a table comparing each of the different types of interfaces and their transfer speeds.

I notice in one of the server reports that shows relative down loads vs. page size that the page was using up a lot of bandwidth relative to other pages.

So in order to save a little bandwidth the table was reduced in size by only showing the final version of the expansion bus. Previous versions of a given spec were removed from the table, reducing the size of the page.

Not wanting to lose any data, the complete table was moved to it's own page; Comparing PC Buses.