I am currently using the STM32F103RD processor, which has 14 available filters on the CAN1 bus.
I am connecting to a J1939 bus, and I need to monitor around 20 PGN's. How do I handle setting up the 20 PGN's with only 14 filters available?
These 20 PGN's are not sequential, so I can't setup a specific range to allow. These 20 may be all over the place.
You have 14 filter banks, but each of those banks can match two distinct PGNs using identifier list mode (FBMx=0). So you can actually match up to 28 PGNs with this part! See section 24.7.4 of the STM32F10x reference manual (page 655) for details.
If you need to match more than 28 PGNs, you have two options:
Pick sets of three or more PGNs and match each of those sets with a single mask-mode filter bank. To reduce the number of unwanted messages that are matched, you will need to pick the sets of matched PGNs carefully (i.e, keep the number of "don't care" bits in the resulting mask to a minimum). Since J1939 is relatively slow, though, filtering some unwanted messages out in software shouldn't be a huge burden.
Use a connectivity-line STM32 part, such as the STM32F107VC. These parts have double the number of CAN filter banks.
I got it working using the list mode. The tricky part is that PGNs need to be shifted around into a 32-bit header so that it can match the "CAN_RI0R" register to trigger an interrupt. For example, I want to receive Engine RPM which is PGN 61444 (0xF004). This needs to be converted into the following header:
0xC7802004
How to compute this:
Start with PGN 61444 (0xF004)
Shift it left by 8 bits so that it is in the correct J1939 Frame Format location.
OR it with 0x0018000000
Shift it left by 3 bits so that it matches the STM32 register locations for STID/EXID.
OR it with 0x4 to set the "Extended" bit indicating that it is an extended header.
The only caveat with this method, versus the mask mode is that as far as I know, you can only receive messages from one single ECU, since the source address is included in the header, and it must match exactly. Meaning, you can only receive messages from the Engine ECU (0x00). For example, 0x18F004XX, where XX is the source address. When using the mask mode, you can ignore the Source Address bits, and receive the PGN from any ECU.
Related
While unit testing a Modbus driver I'm writing I experienced the following:
I can read holding registers 0 to 1022.
I can't read holding registers 1022 to 13000. I get an illegal data address error code.
I can read holding registers 13000 to 25000.
I would have expected devices supporting Modbus to behave in one of the following two ways:
Every device supports the full range of addresses from 0x0000 to 0xFFFF.
Every device supports a range of addresses from 0x0000 to N, where N < 0xFFFF.
Do any of you more experienced people know:
Is Assumption 1 or 2 about the expected behavior of Modbus devices correct?
Are there other reasons beside being out of bounds for an address to be an illegal data address?
Both assumptions are false. It's completely up to the device to decide which registers to support. Some devices are nice and support a wide range of registers, even if they're unused. Most that I've used don't, though. They'll use groups of registers, like your device.
Also, not all Modbus devices support all the Modbus function codes. Just because it's defined by the Modbus protocol standard doesn't necessarily mean the device will support it.
The key thing is to stick to the addresses defined in the device's manual. The manual is usually required reading, otherwise you'll just be guessing at the ranges, units, and scaling.
Backgroud:
I'm using Watson Retrieve and Rank/ or Discovery Service to retrieve information from user manuals. I performed the training with an example washing machine manual in pdf format.
My target is to receive the best passages from the document where a specific natural language string occurs (like "Positioning the drain hose"). Which is working in general.
My problem is that the table of content is almost always the passage with the highest score.
Therefore are the first results just the table of content instead of the relevant text passage. (See example results)
"wrong" result (table of content):
Unpacking the washing machine ----------------------------------------------------2 Overview of the washing machine --------------------------------------------------2 Selecting a location -------------------------------------------------------------------- 3 Adjusting the leveling feet ------------------------------------------------------------3 Removing the shipping bolts --------------------------------------------------------3 Connecting the water supply hose ------------------------------------------------- 3 Positioning the drain hose ----------------------------------------------------------- 4 Plugging in the machine
"correct" result
Positioning the drain hose The end of the drain hose may be positioned in three ways: Over the edge of a sink The drain hose must be placed at a height of between 60 and 90 cm. To keep the drain hose spout bent, use the supplied plastic hose
possible Solutions
ignoring the table of content during training process
offset parameter to e.g. ignore the first 3 results
find out whether the result is part of table of content and ignore if YES
Those approaches are static and don't applicable for multiple documents with various structures (table of content at the beginning/ at the end/ no table of content, ...).
Has someone an idea to better approach this topic?
At this time, passage retrieval results are not affected by relevancy training. As passage retrieval always searches the entire corpus, unfortunately the only reliable way of excluding passage retrieval results from a table of contents is to remove the table of contents.
I have a product that is basically a USB flash drive based on an NXP LPC18xx microcontroller. I'm using a library provided from the manufacturer (LPCOpen) that handles the USB MSC and the SD card media (which is where I store data).
Here is the problem: Internally the LPC18xx has a 64kB (limited by hardware) buffer used to cache reads/writes which means it can only cache up to 128 blocks(512B) of memory. The SCSI Write-10 command has a total-blocks field that can be up to 256 blocks (128kB). When originally testing the product on Windows 7 it never writes more than 128 blocks at a time but when tested on Linux it sometimes writes more than 128 blocks, which causes the microcontroller to crash.
Is there a way to tell the host OS not to request more than 128 blocks? I see references[1] to a Read-Block-Limit command(05h) but it doesn't seem to be widely supported. Also, what sense key would I return on the Write-10 command to tell Linux the write is too large? I also see references to a block limit VPD page in some device spec sheets but cannot find a lot of documentation about how it is implemented.
[1]https://en.wikipedia.org/wiki/SCSI_command
Let me offer a disclaimer up front that this is what you SHOULD do, but none of this may work. A cursory search of the Linux SCSI driver didn't show me what I wanted to see. So, I'm not at all sure that "doing the right thing" will get you the results you want.
Going by the book, you've got to do two things: implement the Block Limits VPD and handle too-large transfer sizes in WRITE AND READ.
First, implement the Block Limits VPD page, which you can find in late revisions of SBC-3 floating around on the Internet (like this one: http://www.13thmonkey.org/documentation/SCSI/sbc3r25.pdf). It's probably worth going to the t10.org site, registering, and then downloading the last revision (http://www.t10.org/cgi-bin/ac.pl?t=f&f=sbc3r36.pdf).
The Block Limits VPD page has a maximum transfer length field that specifies the maximum number of blocks that can be transferred by all the READ and WRITE commands, and basically anything else that reads or writes data. Of course the downside of implementing this page is that you have to make sure that all the other fields you return are correct!
Second, when handling READ and WRITE, if the command's transfer length exceeds your maximum, respond with an ILLEGAL REQUEST key, and set the additional sense code to INVALID FIELD IN CDB. This behavior is indicated by a table in the section that describes the Block Limits VPD, but only in late revisions of SBC-3 (I'm looking at 35h).
You might just start with returning INVALID FIELD IN CDB, since it's the easiest course of action. See if that's enough?
I'm working on a project where I need to send a value between two pieces of hardware using CoDeSys. The comms system in use is CAN and is only capable of transmitting in Bytes, making the maximum value 255.
I need to send a value higher than 255, I'm capable of splitting this over more than one byte and reconstructing it on the receiving machine to get the original value.
I'm thinking I can divide the REAL value by 255 and if the result is over 1 then deconstruct the value in to one byte holding the remainders and one byte holding the amount of 255's in the whole number.
For example 355 would amount to one byte of 100 and another of 1.
Whilst I can describe this, I'm having a really hard time figuring out how to actually write this in logic.
Can anyone help here?
This is all handled for you in CoDeSys if I understand you correctly.
1. CAN - Yes it's in byte but you must not be using CANopen you are using the low level FB that ask you to send a CAN frame of an 8 byte array?
If it is your own two custom controllers ( you are programming both of them in CoDeSys) just use netvariables. Netvariables allows you to transfer any type of variable and you can take the variable list from one controller and import it to another controller and all the data will show up. You don't have to do any variable manipulation it's handle under the hood for you. But I don't know the specifics of your system and what you are trying to do.
If you are trying to deconstruct construct variables from one size to another that is easy and I can share that code with you.
In wikipedia the image of ethernet frame includes a field "inter-packet gap". Other sited I've looked in don't have that field. I don't seem to understand if the gap is predefined according to the protocol or it can be changed using this field.
The default gap between packets is 96 "bit times" (the time taken to send 96 bits on the medium used).
This is sometimes too big or too small in very specialised circumstances, so organisations are allowed to override this by specifying their own.
By including this field, you're effectively telling the recipient, "I'm not going to send anything for n bit times now, please do the same".
Apparently, it's too small for some Ethernet connections on MS Windows and can be changed
here