enso wrote:
[USB] requires a working computer system with substantial resources, the opposite of what you need in an embedded or experimental system.
Not true. I built embedded systems with EZ-USB from Cypress. It is a very popular chip originally developed by Anchor which Cypress acquired. I used the FX and FX2 versions. (The newest version is FX3.) The working USB system consists of a single chip plus a few capacitors. There are no "substantial resources" involved. The chip has 16 kB RAM and it is enough for a very substantial project. The FX2 software can be very simple because most of the USB protocol is handled internally by the ASIC part of the chip. A page or two of code is sufficient for a simple system. Example software is provided in FX2 documentation. A more complex one can use an embedded OS which Cypress named Frameworks. It is neat, small, well written in plain C, and very well documented. The FX2 Technical reference manual is an outstanding source of knowledge both on the chip and on the USB protocol and architecture.
An asynchronous serial port sends data when it's ready,
Not that simple. A good reference book will explain a bit more. I recommend Patterns for Time-Triggered Embedded Systems by Michael Pont (available from Amazon). This book is very much in Oberon spirit. I once wrote to Michael Pont that his architecture is very close to Oberon System. He never heard of Oberon prior to my e-mail, but he checked and acknowledged the similarity. His software provides an example how Oberon System could have been if it was supported by a good industrial manager like Michael.
whereas USB has to packetize the data, causing unnecessary processing and making the timing less certain.
Let me point out that the USB-2 can achieve about 25 MBytes per second. It supports up to 256 devices on a single bus. It has extensive identification of devices and it can load and execute drivers. Saying that these features are "unnecessary processing" is not even wrong. USB-3 is even more impressive, but I am not an expert on USB-3. My working knowledge only covers (parts of) USB-2.
A serial port was an always-ready peripheral, easily configured with a couple of registers.
One host and a single peripheral. It is not much. As soon as you want to develop something more substantial (like a network) "easily" does not apply anymore. You must read a few books. I recommend Serial Port Complete by Jan Axelson, or the Pont's book pointed above.
Initializing a USB connection requires extensive negotiation and large tables, requiring kilobytes of RAM and a working CPU.
Use EZ-USB and USB will become almost as simple as the serial port. All you need is some easy reading. The USB Complete by Jan Axelson is a good beginning, and then the first few chapters from the FX or FX2 Technical Reference Manual will put you on a path to success. The FX/FX2 chips will take care of "extensive negotiation" for you. It is very easy. Just a couple books and a couple months and you will become a proficient USB developer, if you are not one already.
Attaching a simple HID device like a keyboard, for those who complain about PS/2 ports, is not that easy.
Use the Cypress chip to handle the complexity and off you go. Also check the following page: http://janaxelson.com/index.html You can also use FTDI if you want a canned solutions. I recommend Cypress because with Cypress you can take the lid off if you want to.
Finally, as ubiquitous as USB is, it is not something that should be 'taught'. It is a dumb, bloated and obfuscated spec with multiple standsards, connectors and extensions that is much like the US tax code.
I thought this mailing list was for engineers. I am surprised to find a politician among us. Thank you, Wojtek
Wojtek, I had a "run-in" with the Cypress FX2 about 5 years ago. I was forced to use it because it was used on my then employers previous product. I am not a natural C programmer, and forced to having to use this IC I guess put about 3 months on the project. The FX2 is a 8051 based microcontroller You need to get hold of the C compiler - Keil uVision - at whatever cost You have to fight your way around the 8051 architecture I never did come to terms with the code that ran the USB - I just accepted that was present on the device, and tried to concentrate on getting my application to work. I ended up implementing bit-banged SPI on the FX2, to copy a few bytes into a serial SRAM, for which I created a dual port arrangement to the C2000 DSP I was using. Did I learn anything useful about USB from my FX2 experience? - just never use an 8051 or FX2 ever again! The FX2 adds about $5 the product. There's really no place left for it nowadays when you can by an easy to use USB to serial converter IC for under $0.50, and every ARM chip from $1.50 upwards has USB on chip. I am a solid proponent of keep it simple. I am pleased to add Nicklaus Wirth to my shortlist of computer heroes, including Charles H. Moore, Gordon Bell, Ed de Castro - who offer a voice of sanity in an otherwise insane world. On 17 February 2016 at 04:56, <skulski@pas.rochester.edu> wrote:
enso wrote:
[USB] requires a working computer system with substantial resources, the opposite of what you need in an embedded or experimental system.
Not true. I built embedded systems with EZ-USB from Cypress. It is a very popular chip originally developed by Anchor which Cypress acquired. I used the FX and FX2 versions. (The newest version is FX3.) The working USB system consists of a single chip plus a few capacitors. There are no "substantial resources" involved. The chip has 16 kB RAM and it is enough for a very substantial project.
The FX2 software can be very simple because most of the USB protocol is handled internally by the ASIC part of the chip. A page or two of code is sufficient for a simple system. Example software is provided in FX2 documentation. A more complex one can use an embedded OS which Cypress named Frameworks. It is neat, small, well written in plain C, and very well documented.
The FX2 Technical reference manual is an outstanding source of knowledge both on the chip and on the USB protocol and architecture.
An asynchronous serial port sends data when it's ready,
Not that simple. A good reference book will explain a bit more. I recommend Patterns for Time-Triggered Embedded Systems by Michael Pont (available from Amazon). This book is very much in Oberon spirit. I once wrote to Michael Pont that his architecture is very close to Oberon System. He never heard of Oberon prior to my e-mail, but he checked and acknowledged the similarity. His software provides an example how Oberon System could have been if it was supported by a good industrial manager like Michael.
whereas USB has to packetize the data, causing unnecessary processing and making the timing less certain.
Let me point out that the USB-2 can achieve about 25 MBytes per second. It supports up to 256 devices on a single bus. It has extensive identification of devices and it can load and execute drivers. Saying that these features are "unnecessary processing" is not even wrong.
USB-3 is even more impressive, but I am not an expert on USB-3. My working knowledge only covers (parts of) USB-2.
A serial port was an always-ready peripheral, easily configured with a couple of registers.
One host and a single peripheral. It is not much. As soon as you want to develop something more substantial (like a network) "easily" does not apply anymore. You must read a few books. I recommend Serial Port Complete by Jan Axelson, or the Pont's book pointed above.
Initializing a USB connection requires extensive negotiation and large tables, requiring kilobytes of RAM and a working CPU.
Use EZ-USB and USB will become almost as simple as the serial port. All you need is some easy reading. The USB Complete by Jan Axelson is a good beginning, and then the first few chapters from the FX or FX2 Technical Reference Manual will put you on a path to success. The FX/FX2 chips will take care of "extensive negotiation" for you.
It is very easy. Just a couple books and a couple months and you will become a proficient USB developer, if you are not one already.
Attaching a simple HID device like a keyboard, for those who complain about PS/2 ports, is not that easy.
Use the Cypress chip to handle the complexity and off you go. Also check the following page: http://janaxelson.com/index.html
You can also use FTDI if you want a canned solutions. I recommend Cypress because with Cypress you can take the lid off if you want to.
Finally, as ubiquitous as USB is, it is not something that should be 'taught'. It is a dumb, bloated and obfuscated spec with multiple standsards, connectors and extensions that is much like the US tax code.
I thought this mailing list was for engineers. I am surprised to find a politician among us.
Thank you, Wojtek
-- Oberon@lists.inf.ethz.ch mailing list for ETH Oberon and related systems https://lists.inf.ethz.ch/mailman/listinfo/oberon
Finally, as ubiquitous as USB is, it is not something that should be 'taught'. It is a dumb, bloated and obfuscated spec with multiple standsards, connectors and extensions that is much like the US tax code.
I thought this mailing list was for engineers. I am surprised to find a politician among us.
You've never gotten a single email from my account yet, have you? Take me off filter.
participants (3)
-
Ken Boak -
Lars -
skulski＠pas.rochester.edu