First Batch of PCBs (assembled)

I’ve been slowly working on a bunch of PCBs, and the first batch is finally here.

In the coming weeks, I will discuss each board in more detail, fill in the trac pages, and add the Eagle PCB files to my subversion repository.  I will also cover any mistakes I find, and possible improvements.

The initial lineup consists of the:

• FP-SMC-1, which is finally here!  It’s a demo board designed to show how to design a custom PCB to replace typical control cabinet wiring.  It connects a Panasonic FP series PLC to a SMC pneumatic manifold.
• CO-DB9-RJ45-2, designed to convert a CANOpen DB9 connector to dual RJ45 connectors.
• CO-HDR-RJ45, designed to convert a CANOpen terminal block header to dual RJ45 connectors.
• CO-M12-RJ45, designed to convert a CANOpen M12 connector to dual RJ45 connectors.
• CO-TB-RJ45, designed to convert a CANOpen terminal block to dual RJ45 connectors.

Summary: 8.0/10,  recommended reading if you are developing systems using CAN or higher level protocols such as CANOpen.

The Guide is an affordable (<$15) book on the low level details of the CAN protocol.  It covers in detail the different frame types (data, remote, error, and overload), network arbitration, error detection and recovery, and data transfer synchronization.

The Guide points out undefined or ambiguous areas in the official specifications (Bosch, ISO, CiA), including updates based on experience (such as the CiA’s recommendation not to use remote frames).   The book concentrates on the base CAN protocol; it does not cover higher level protocols (such as CANOpen) in any detail, nor does it describe the specifics of CAN controllers or transceivers.

The book is well written; I’m an automation software developer, not a low level embedded developer, but I was able to follow the explanations without any major problems — I’d say it was easier to read than many software development books.

If all you want to do is get a basic CANOpen control system running, then you can skip this book.  But if you to truly understand CAN and what it can do, then I highly recommend reading both this book and Embedded Networking with CAN and CANOpen. Here are some things I learned from the Guide:

• How fast CAN really is  (data throughput, error recovery time, etc), including protocol overhead, for both standard and extended addressing.  Serial network protocols have a substantial overhead.
• Termination resistors have be able to dissipate at least 220 mW.
• Terminators should be at the network ends, not inside the CAN device.
• The details of error counting and error frames.  I had been wondering what the Copley CMO library’s ErrorFrameCounter property really meant; now I know.
• The meaning of the bit time segments  and how bit resynchronization works.  The Grid Connect (aka Acacetus) CAN-USB Light manual refers to the bit segments (sync_seg, prop_seg, phase_seg1, phase_seg2, SJW, etc) but didn’t explain them.  Now I understand bit segments.

The Guide’s network topology recommendation (straight line topology with minimal stub lines with terminators at the ends) match what I already do.  I was happy to see the correct recommendation for shielded cables (connect the shield at one end only).

I do have some small nitpicks and suggestions for improvement:

• The book is repetitive; the exact same explanations with the same diagrams appear multiple times, as do various notes and warnings.  I find this annoying when reading the book straight through; however, overall, it’s probably good — when using the book as a reference, I want relevant warnings in the section I’m using, not just in one place in the book.
• The diagrams could be better explained; there is no key to explain the dark black lines (high line only means that field is always recessive; low line only means the field is always dominant; both high and low lines means field can be either depending on the message — maybe that’s obvious to hardware guys).
• The diagrams could be clearer: a bit larger with more contrast.
• OK, the book isn’t a comprehensive guide to CAN transceivers.  But I would have appreciated some warnings about common physical layer gotchas.

CANOpen DB9/dual RJ45 adapter

I made sure it will work well with AMC DX15C08 Digiflex drives to convert the DX15C’s DB9M to two RJ45s.  The Phoenix header (in green) is for supplying power to the DX15C’s isolators.  Since I will probably make some more changes (for one, I don’t think there is room to screw the adapter’s DB9F to a DB9M), I am not posting the design files yet.

So I installed the latest Ixxat VCI drivers (V3) and then verified my Ixxat USB-to-CAN compact was working by sending and received CAN messages.  I installed CMO 2.5, fired up MS Visual Studio, ran the Copley example, and got this exception:  Access is denied.  (Exception from HRESULT: 0×80070005 (E_ACCESSDENIED).  Hmmm.  I started VB6, ran the VB6 example, and received this error: Permission denied, which looks like another way of saying E_ACCESSDENIED.

I contacted Copley.  The answer: CMO V2.5 only supports Ixxat using the older (VCI V2) drivers.  In the future, CMO will support VCI V3, but not yet.

So then I try installing VCI V2 – and had problems communicating with the Ixxat (error 0×1F hardware error).  I contacted Ixxat, and went through their recommended procedure:

1. Uninstall VCI V2 drivers, then reboot.
2. Uninstall VCI V3 drivers, then reboot.
3. Run Ixxat’s VCI Clean program to clean up any stuff left in the registry and on the computer, then reboot.
4. Re-install VCI V2 drivers.

Even after that procedure, I still couldn’t get the VCI 2 drivers to work.  I suspect it might be a problem with Windows and my particular USB controllers, but it’s not worth troubleshooting since the Ixxat is working fine with the VCI V2 drivers on a nearby computer.

In the future, I’ll install the VCI V2 drivers first, then VCI V3 (normally you can switch between them).

Ixxat, Acacetus, and Peak CAN Interfaces

I now have three CAN interfaces.  I plan on doing tests on all three to measure their performance.

The Acacetus (also sold by Grid Connect as the CAN USB Light) is the least expensive ($100).  It communicates via a virtual COM port.  So far I’ve used HyperTerm to communicate with it, which doesn’t work well (binary data isn’t intelligible, etc).  Using a serial library should work better.

The CAN and virtual COM port settings are accessed by resetting the device, and then going through a series of menus.  The CAN baud rate isn’t set directly; instead you set the various detailed parameters; fortunately, I found a handy table, but I much prefer Ixxat’s approach (pick the baud rate, and then tweak if you want).

So far, it works, but doesn’t seem in the same class as the Peak or Ixxat – it doesn’t feel as well built, and is more limited (e.g. can’t set baud rate remotely).  It only comes with driver software.

The Peak is a parallel port dongle; I much prefer a USB connection, but I didn’t pay for the Peak.  It has a keyboard pass-through connector to provide enough power.  It is sold in the US by Grid Connect and Phytec for $249.  The Peak USB to CAN is $279, but is worth the extra money.

The Peak interfaces come with PCAN Light driver, and PCANView which is a simple program to send and receive CAN messages.  The extra cost, advanced driver has some nice features, such as sharing a CAN interface among multiple applications.

Right now, the Peak is handy because I have PCANOpen Magic Lite for it (it was included with the CANOpenIA-XA kit I have), which provides some basic CANOpen functionality.  It has many restrictions; for example, it only supports CANOpen address 0×40 to 0×4F, so I had to remap my Copley drives to this address range.

The Ixxat USB-to-CAN compact is the most expensive ($335 from CAN Connection).  It comes with drivers and some helper programs, including one similar to PCANView, but does not include any CANOpen specific software.  I talked about it in my previous post.

Ixxat Box

I recently received an impressive blue ESD safe box.  Inside was the  Ixxat USB-to-CAN compact interface which I had ordered from the CAN Connection store.

So why spend the money on the Ixxat when I already have two CAN interfaces?  Software support.  I decided I needed a CAN interface which is supported by the manufacturer’s setup and tuning software.

I like USB to CAN interfaces – I do not having to open up my computer to plug cards in (although I do wish USB connectors could lock – it’s very easy for them to become disconnected if I have to move my computer around).  I’d like an Ethernet to CAN interface even better, but the only semi-affordable ones I know of are the Anagate CAN interfaces (about $300-$450), which are only supported by CANFestival (but not by AMC, Copley, Elmo, etc).

Only Kvaser and Ixxat CAN interfaces are supported by all of the CANOpen servo drives I own (AMC, Copley, Elmo), so I decided to buy either a Ixxat USB-to-CAN compact or a Kvaser Leaf Light.  I decided to buy the Ixxat because:

1. I like the Ixxat physical arrangement better (only the USB cable is permanently attached).
2. Kvaser currently does not have a CANFestival driver, which is very important since I plan on using CANFestival.
3. Faulhaber and Maxon support Ixxat but not Kvaser.

Ixxat USB to CAN compact

My Ixxat does have a quality feel to it, and unlike many CAN interfaces, does pack substantial processing power (a 24MHz Infineon C161 with 128K SRAM and 512K flash).  It is available with either a single RJ45 or single DB9M connector.  I choose the DB9M version since my other CAN interfaces use DB9M connectors.

Right now I am using the Ixxat with the Copley CMO COM library.  One quirk – Copley supports Ixxat in their CMO and CML libraries, but not in CME2 (Copley’s setup and tuning application).  Copley supports Kvaser in all three.

CME2 is needed to setup the drives.  The CAN baud rate has to be set from CME2, as well as the amplifier settings such as Hall sensor settings.  However, it’s easy to connect using the Copley’s serial port and a properly wired RJ12 to DB9F cable.

The Festo CPV-10-GE-CO-8 CANOpen valve terminal has a DS303-standard 5-pin M12 plug (male) connector. The second generation Festo valve terminal (CPV-10-GE-CO2-8) allows the choice of
DB9, M12, and terminal block. In my CANOpen research so far, the most common connectors are DB9, RJ45, M12 (for harsh environments), and terminal block (especially for I/O).

My preference is dual RJ45 connectors for normal environments, and dual M12 connectors for harsh environments. M12 connectors are typically IP67 rated, are available with 3, 4, 5, and 8 pins, can be shielded or unshielded, are quick to connect (unlike most DB9’s), and are vibration resistant. M12 connectors are used most often to connect sensors back to a controller, often via a concentrator or fieldbus box. Other uses include CANOpen (of course), DeviceNet, Profibus, and Banner light curtains.

Since nothing stays simple, there are a number of M12 variations. The ERNI catalog lists five polarizations: A,B,C,D, and P. The A or normal polarization is the most common, and is used by most sensors and CANOpen; the B (or reverse; used for Profibus) and D (used for Ethernet) polarizations are available, but not as common.

I looked at M12 connectors and cordsets from Phoenix, Binder USA, Lumberg, ifm efector, ERNI, Turck, Hirschmann and Tyco/AMP. It’s interesting to see what is available that could be used with CANOpen
systems.

Connector availability is good, with plenty of choices for PCB mount, free-hanging, and bulkhead mount in male, female, and right angle versions. Single-ended cordsets with a male straight, male right angle, female straight, or female right angle connector are common.

However, I only found Male/Female double ended cordsets; I have not found any Male/Male or  Female/Female cord sets. All the Tees I found had 1 male and 2 female connectors. I think this comes from M12 connectors use in sensors. Extension cables have to be M/F. A 1M/2F Tee splits one female connector into two female connectors, allowing two sensors to be wired to one connector (most sensor boxes use female connectors, and some do support two inputs to one connector).

This can work well for CANOpen systems, too. DS303 does not provide guidance on how to connect the whole system, but DS102 does for DB9 connectors. Applying the Interconnected Bus Line approach from DS102 works perfectly for M12 connectors: start off with a M12 female terminator, connected to M/F cable. The cables are connected together using a Tee (with 1 male, 2 female connectors) for devices with 1 male M12 connector (with one of the Tee’s female connectors connected directly to the device’s M12 male
connector or via a M/F stub line cord set), and connected directly to the device for devices with Male & Female M12 connectors. The bus ends with a M12 male terminator.

The parts required are available, except perhaps for the female terminator (but that can be made easily). However, compared to RJ45 cables, the cost is high. Using Allied Electronics pricing (8/17/08) for Phoenix, a male terminator (1507816) is $17.96, a CANOpen Tee (1507793) is $44.91, a Sensor/Actuator Tee (1683468) is $24.06, a CANOpen M/F 0.3m shielded cable (1518258) is $47.72, and a 0.3m M/F Sensor/Actuator cable (1519040) is $21.70, and a shielded 0.3m Sensor/Actuator cable (1500884) is $31.49. Long cables don’t cost
a lot more; for example, a 3m Sensor/Actuator M/F shielded cable (1500910) is $40.04. I’m not sure what the difference is between Phoenix’s recommended CANOpen cable and the “Sensor/Actuator” shielded cable, or between the “CANOpen” Tee and the “Sensor/Actuator” Tee.

Tony

The Festo CPV series is a modular pneumatic valve system, consisting of a base, side panels, up to 8 valves, and a valve terminal top plate. The valve terminal can be directly wired to each valve solenoid, or it can be a fieldbus interface such as CANOpen, DeviceNet, ASI, or Profibus. The second generation valve terminals have an added “2″ (so the new CANOpen valve terminal is CPV-10-GE-CO2-8), and some added features, such as more connector options (the CO has only one option: a single M12; the CO2 can use DB9M, dual M12, or terminal block), and a connector for adding additional CPV valve blocks to the same fieldbus interface.

Searching on google for model name (CPV-10-GE-CO-8 or CPV10-GE-CO-8) and number (175481) didn’t turn up anything useful. You have to search on Festo’s website using the full text search. For example, searching for CANOpen returns the Info 219 document (Festo CANOpen products overview) and on page 3, the CPV-10-GE-CO-8 manual in English, but not the CPV-10-GE-CO2-8 manual.

The best way is to use Festo’s full text search with the manual part number or  manual designation. The problem is to know what the manual part number or designation is. Fortunately you do not have to guess; that information is available from other sources, such as the Info 201 PDF (Fieldbus Direct products) and Info 219. For older products, it’s fortunately that Festo is logical; the second generation valve terminal’s manual designation is P.BE-CP-CO2-EN, and the original product’s manual designation is P.BE-CP-CO-EN.

The same logic applies if you are trying to find information on other Festo products, such as the CPV10-GE-DN2-8 DeviceNet valve terminal – you need to find the manual designation (in Info 201 or Info 218 (DeviceNet products)), and do a full text search on Festo’s website using the manual designation.

Here are some direct links to the Festo CANOpen information (all links are to PDF’s):

• Info 213 CPV system product catalog
• Info 201 CPV Fieldbus Direct product catalog
• Info 219 CANOpen products catalog
• CPV pneumatics manual, designation P.BE-CPV-EN, part number (or order number) 165 200
• CPV-10-GE-CO-8 manual, designation P.BE-CP-CO-EN, part number 175 580
• CPV-10-GE-CO2-8 manual, designation P.BE-CP-CO2-EN, part number 526 010