Req: Microcontroller Recommendation
in [Embedded]
|
Prev: How to use E or F ports as Serial port in RCM 3700
Next: Call for Papers: PDPTA'10 (The 2010 International Conference on Parallel and Distributed Processing Techniques and Applications), USA, July 2010
From: D Yuniskis on 12 Feb 2010 01:49 Veekster wrote: > Hello my most esteemed colleagues, > > I'm designing a sensor interface circuit that has gain and filtering > options that need to be set by latching a parallel set of bits. I > want to control this remotely with a serial interface of some type (to > reduce conductor count). I'm thinking I need a simple microcontroller > with a serial interface (usart?) to do this easily. > > Additionally, a microcontroller with a sleep mode that shuts down the > clocks would enhance low noise measurement performance, so that's a > requirement. Ideally it would wake up on serial interface activity. > > Would you geniuses care to recommend a simple microcontroller (or an > alternate approach) that would do the job? > > The simple tinyAVR and PIC controllers seem to have too many > peripherals and are overkill, but maybe that's no big deal. We're > only building ~1000 of these. You haven't indicated: - how much data you need to send - *if* you need to receive anything *back* - the distances involved - the data rates - the "sample" rates (as different from data rates) - power available - what's going to be on the "other" (host) end etc. There are *lots* of "serial interfaces" -- each with particular characteristics for all of the above criteria.
From: Paul Carpenter on 12 Feb 2010 05:24 In article <a18c5669-f941-4ca0-96e5- 8e1e9e21573a(a)v36g2000vbs.googlegroups.com>, to.vic.man(a)gmail.com says... > Hello my most esteemed colleagues, > > I'm designing a sensor interface circuit that has gain and filtering > options that need to be set by latching a parallel set of bits. I > want to control this remotely with a serial interface of some type (to > reduce conductor count). I'm thinking I need a simple microcontroller > with a serial interface (usart?) to do this easily. If you have other processing such as is suggested with the serial interface, and the sensor output goes to something else, would not a simple PCF8574 do the job? I.e. I2C 8 bit I/O port in a SO16 on your design, with a clock ONLY used when talking to the latch. There is also a PCF8575 which is 16 bit I/O port at 400kHz, so you can have more bits and read back inputs as well. If you need even more bits than that they can be added on the same I2C bus as you can have 8 x PCF8574 on the same bus and another 8 x PCF8575A on the same bus (that is 16 x 8 bits of I/O). Then consider how many I/O's you get from PCF8575 in less SSOP24 devices. Done this sort of thing before for sensors that need no noise from other parts of the system. > Additionally, a microcontroller with a sleep mode that shuts down the > clocks would enhance low noise measurement performance, so that's a > requirement. Ideally it would wake up on serial interface activity. Where and how is the sensor output measured? A shut off I2C bus, and good supply filtering (which you will need anyway) is good for that. > Would you geniuses care to recommend a simple microcontroller (or an > alternate approach) that would do the job? Unless the micro is going to do the actual measurement or other task I would choose the I2C or similar route. > The simple tinyAVR and PIC controllers seem to have too many > peripherals and are overkill, but maybe that's no big deal. We're > only building ~1000 of these. A PCF8574 is cheap, been around for ages (and likely to be for a long time), you could even replicate one in a small PLD if it become obsolete and the second sources dried up. PLD route gives you possibility of 32 bit or larger I/O port, also means you can make your I2C match ANY of the I2C spec speeds or your own speed only. Run your serial as I2C specific to that sensor only (or group of similar sensors). If really worried you can find wys to opto/galvanically isolate I2C or SPI, to really isolate them. -- Paul Carpenter | paul(a)pcserviceselectronics.co.uk <http://www.pcserviceselectronics.co.uk/> PC Services <http://www.pcserviceselectronics.co.uk/fonts/> Timing Diagram Font <http://www.gnuh8.org.uk/> GNU H8 - compiler & Renesas H8/H8S/H8 Tiny <http://www.badweb.org.uk/> For those web sites you hate
From: antedeluvian on 12 Feb 2010 16:18 >I'm designing a sensor interface circuit that has gain and filtering >options that need to be set by latching a parallel set of bits. I >want to control this remotely with a serial interface of some type (to >reduce conductor count). I'm thinking I need a simple microcontroller >with a serial interface (usart?) to do this easily. > From what you are asking, I am not sure if the circuitry you have must be external to the micro. The PSoC for one will allow you to contain PGAs (programmable gain) Instrumentation Amplifiers and filters all on board. They are changed by simple API calls and can even be dynamically re-allocated to a completely different configuration. It does have a sleep mode as well. No other micro has quite the versatility of the PSoC in terms of its configuration and re-configuration, but there must be others with programmable gain and filtering- try Silicon Labs for an 8051 based device and also Analog Devices had some lower end products that may fit the bill. -Aubrey --------------------------------------- Posted through http://www.EmbeddedRelated.com
From: Veekster on 18 Feb 2010 13:07 On Feb 12, 2:24 am, Paul Carpenter <p...(a)pcserviceselectronics.co.uk> wrote: > In article <a18c5669-f941-4ca0-96e5- > 8e1e9e215...(a)v36g2000vbs.googlegroups.com>, to.vic....(a)gmail.com says... > > > Hello my most esteemed colleagues, > > > I'm designing a sensor interface circuit that has gain and filtering > > options that need to be set by latching a parallel set of bits. I > > want to control this remotely with a serial interface of some type (to > > reduce conductor count). I'm thinking I need a simple microcontroller > > with a serial interface (usart?) to do this easily. > > If you have other processing such as is suggested with the serial > interface, and the sensor output goes to something else, would > not a simple PCF8574 do the job? > > I.e. I2C 8 bit I/O port in a SO16 on your design, with a clock ONLY used > when talking to the latch. There is also a PCF8575 which is 16 bit I/O > port at 400kHz, so you can have more bits and read back inputs as well. > > If you need even more bits than that they can be added on the same I2C > bus as you can have 8 x PCF8574 on the same bus and another 8 x PCF8575A > on the same bus (that is 16 x 8 bits of I/O). Then consider how many > I/O's you get from PCF8575 in less SSOP24 devices. > > Done this sort of thing before for sensors that need no noise from other > parts of the system. > > > Additionally, a microcontroller with a sleep mode that shuts down the > > clocks would enhance low noise measurement performance, so that's a > > requirement. Ideally it would wake up on serial interface activity. > > Where and how is the sensor output measured? > > A shut off I2C bus, and good supply filtering (which you will need > anyway) is good for that. > > > Would you geniuses care to recommend a simple microcontroller (or an > > alternate approach) that would do the job? > > Unless the micro is going to do the actual measurement or other task > I would choose the I2C or similar route. > > > The simple tinyAVR and PIC controllers seem to have too many > > peripherals and are overkill, but maybe that's no big deal. We're > > only building ~1000 of these. > > A PCF8574 is cheap, been around for ages (and likely to be for a long > time), you could even replicate one in a small PLD if it become obsolete > and the second sources dried up. PLD route gives you possibility of 32 > bit or larger I/O port, also means you can make your I2C match ANY of the > I2C spec speeds or your own speed only. > > Run your serial as I2C specific to that sensor only (or group of similar > sensors). > > If really worried you can find wys to opto/galvanically isolate I2C or > SPI, to really isolate them. > > -- > Paul Carpenter | p...(a)pcserviceselectronics.co.uk > <http://www.pcserviceselectronics.co.uk/> PC Services > <http://www.pcserviceselectronics.co.uk/fonts/> Timing Diagram Font > <http://www.gnuh8.org.uk/> GNU H8 - compiler & Renesas H8/H8S/H8 Tiny > <http://www.badweb.org.uk/> For those web sites you hate Paul, Thank you for your suggestions, I'm reading the data sheets you sent! Thanks everyone for your help! Vic
From: Ulf Samuelsson on 9 Mar 2010 17:56
Veekster skrev: > Hello my most esteemed colleagues, > > I'm designing a sensor interface circuit that has gain and filtering > options that need to be set by latching a parallel set of bits. I > want to control this remotely with a serial interface of some type (to > reduce conductor count). I'm thinking I need a simple microcontroller > with a serial interface (usart?) to do this easily. > > Additionally, a microcontroller with a sleep mode that shuts down the > clocks would enhance low noise measurement performance, so that's a > requirement. Ideally it would wake up on serial interface activity. > > Would you geniuses care to recommend a simple microcontroller (or an > alternate approach) that would do the job? > > The simple tinyAVR and PIC controllers seem to have too many > peripherals and are overkill, but maybe that's no big deal. We're > only building ~1000 of these. Most people I talk to about sensors tend to end up with an ATxmega16/32A4. Mainly due to the 12 bit ADC with programmable gain. Nice sleeps modes. If you set the pin change interrupt on the UART RXD you can wake up. -- Best Regards Ulf Samuelsson These are my own personal opinions, which may or may not be shared by my employer Atmel Nordic AB |