Gateway device
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Is 16Mhz really a must have? The reason for my question, is that it seems that it would be more advisable to run the entire thing at 3.3V supply, as most of the peripherals that I have found, is running at that supply level.
That goes with : nrf24, SPI flash, wifi module, etc. So considering the peripherals I would suggest to run everything on 3.3V. However, this also means that we might have to lower the crystal frequency slightly, to 12Mhz, instead of 16Mhz, to keep it inside the specs.
Anyways, just a question. while browsing datasheets :)
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I agree. It is the center of the sensorweb. I think it pays to keep it running on full steam. And even if it is running of mains, and certainly is not suitable for battery powered operation, it still will draw a fraction of a lightbulb so hunting milliwatts makes little difference in the long runt I think. Besides, it will be bitter if we end up with performance limitations when we now "solve" the memory limitations.
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well the reason to shift to 3.3v was that it would make things a whole lot easier, when interfacing with the different peripherals. It is not for hunting mA's.
But I'll dump some simple level shifting in there then.
@tbowmo ethernet/wifi/nordic at least are tolerant mostly to 5V
the only complication is to have two supplies
taking into account many different required things two supplies is not a major complication
while keeping arduino & atmel....but if shift to something else (stm32 for example) 3.3V are sufficient even for 72MHz
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well the reason to shift to 3.3v was that it would make things a whole lot easier, when interfacing with the different peripherals. It is not for hunting mA's.
But I'll dump some simple level shifting in there then.
@tbowmo I see. But a simple stab to get 3.3V should be fairly cheap. And also "safe". I found that I could not get reliable RF on my Ethernet GW, so I threw in a LE33 just to power the radio (I use the PA-pimped one which is a bit more nitpicky on the supply). Have not had power issues since. So it could be that regulating the RF will be required anyway since I assume that PA-pimped radios will be part of the "offering".
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It's more the external SPI flash, I haven't been able to find any that works above 3.6V, where they specify abolute maximum voltage on any pin to be 4.1V. I haven't looked at the datasheet for ethernet / wifi modules yet, so there also might be some problems there with maximum ratings on input signals.
@Anticimex
I have already thrown in a 3.3V supply for the radio, and what else is needing 3.3V to operate.Anyways, I have thrown in a resistor / diode "matrix", to do level shifting on SPI signals now..
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@tbowmo Did you consider using a ESP8266 WIFI Module?
You can easily program it and get the atmega off the part's list.How to directly program an inexpensive ESP8266 WIFI Module @ Hackaday.com
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I fear that it will take too much time, if we have to port the library to the esp8266 cpu core. But you are more than welcome to dig in to it, if you feel for it :)
Currently the focus is (more or less) on arduino compatible platforms.
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After finish my rpi gateway i think i will focus on the esp. I just wait for some local sellers to drop their prices(Easter, etc)
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I've started using KiCad for this project.. Still it's far from completed (things are progressing more slowly with this one, than the last, as it's a bit more complex and I don't have that much time at hand now..
Anyway, I have created a github repository of it, if anyone wants to have a look, https://github.com/tbowmo/MySensorGW
Current schematics are here (PDF file)
MySensorsGW-schematic.pdfIt's still a Work In Progress.. A lot of stuff needs to be ironed out..
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I've started using KiCad for this project.. Still it's far from completed (things are progressing more slowly with this one, than the last, as it's a bit more complex and I don't have that much time at hand now..
Anyway, I have created a github repository of it, if anyone wants to have a look, https://github.com/tbowmo/MySensorGW
Current schematics are here (PDF file)
MySensorsGW-schematic.pdfIt's still a Work In Progress.. A lot of stuff needs to be ironed out..
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There will eventually be footprints on there for wifi / ethernet modules.. And Yes I2C should go to a pinheader. SPI is already at a pinheader (kindof). As it's connected to the ISP header :)
I'm trying to get a grip on my thoughts, and create some parts for wifi/ethernet modules.. :)
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So decision time..
For wired ethernet, it seems that we have 2 options:
- w5100
- enc28j60
I haven't got that much experience with theese devices, so which one should we go ahead with?
Wireless, I think that I am settled with esp8266, but if there are anything else out there, that might be better, then please let me know..
At the moment I can't really decide which one is better :) So need some help from the community.
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I use the W5100 on my current gateway, and I have not had any significant issues with it (apart from the infamous SPI issue, which is resolved by controlling the SPI_EN signal to the W5100. Apart from that I am happy with it, and it is intelligent enough to allow the necessary software to fit an Arduino Nano. Unfortunately not with DHCP enabled (and signing support enabled). But if the enc28j60 does not require more software, and handles SPI(?) "properly" perhaps it would be the better alternative?
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@tbowmo thank! it is a good job done!
some questions/comments- w5100 SPI fix is already inside modern arduino ethernet shield http://www.arduino.cc/en/uploads/Main/arduino-ethernet-shield-06-schematic.pdf
do you think it is needed? what kind of the shield your are looking for? - why not to put 20MHz crystal to give some more performance to the gateway?
- USB is normally can supply not more than 500mA, are you sure it will be sufficient? DC-jack probably will be also good to have. ESP+wisnet could be hungry for the supply
- why atmega1284? it is not a standard arduino choice but could costs on a level of 1280. atmega128 is the lowest cost 128k AVR. If we are sure 128k will be sufficient in the future I will select atmega128 because of cost or atmega1280 because it is standard for arduino
And also I will consider atmega2560 to have a maximum possible resources (not only flash but also RAM)
sense and drive
- w5100 SPI fix is already inside modern arduino ethernet shield http://www.arduino.cc/en/uploads/Main/arduino-ethernet-shield-06-schematic.pdf
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@tbowmo thank! it is a good job done!
some questions/comments- w5100 SPI fix is already inside modern arduino ethernet shield http://www.arduino.cc/en/uploads/Main/arduino-ethernet-shield-06-schematic.pdf
do you think it is needed? what kind of the shield your are looking for? - why not to put 20MHz crystal to give some more performance to the gateway?
- USB is normally can supply not more than 500mA, are you sure it will be sufficient? DC-jack probably will be also good to have. ESP+wisnet could be hungry for the supply
- why atmega1284? it is not a standard arduino choice but could costs on a level of 1280. atmega128 is the lowest cost 128k AVR. If we are sure 128k will be sufficient in the future I will select atmega128 because of cost or atmega1280 because it is standard for arduino
And also I will consider atmega2560 to have a maximum possible resources (not only flash but also RAM)
@axillent said:
@tbowmo thank! it is a good job done!
some questions/comments- w5100 SPI fix is already inside modern arduino ethernet shield http://www.arduino.cc/en/uploads/Main/arduino-ethernet-shield-06-schematic.pdf
do you think it is needed? what kind of the shield your are looking for?
I was looking at the cheap Chinese breakout boards with W5100 chip on, not all of them have the SPI fix onboard, so that's why I implemented it.
- why not to put 20MHz crystal to give some more performance to the gateway?
Hmmm.. think it was a price thing.. 16Mhz was more common than 20Mhz. But can't remember it right now (it's been a couple of weeks since I put in the 16Mhz xtal)
- USB is normally can supply not more than 500mA, are you sure it will be sufficient? DC-jack probably will be also good to have. ESP+wisnet could be hungry for the supply
In my thoughts, it should be either W5100 or ESP8266 mounted, not both at the same time (since both is for "internet" access. Also, most phone chargers are delivering 1A and up. Also, if you connect the thing to a computer via USB, you might not want to use W5100 / ESP8266 to communicate with it, so those power eaters could be left out in that case, leaving only NRF and/or RFM69 as radios.
- why atmega1284? it is not a standard arduino choice but could costs on a level of 1280. atmega128 is the lowest cost 128k AVR. If we are sure 128k will be sufficient in the future I will select atmega128 because of cost or atmega1280 because it is standard for arduino
There are some people that are using atmega1284 with arduino IDE, so it can be used. Solderability is the first reason: atmega1280 is 100pins, while atmega1284 is 44 pins, price: atmega1280 is 15.96$, while atmega1284 is 8-9$. Of course I can see the point in putting in 1280, as it could be swapped for a 2560 if more flash/ram is needed.
And also I will consider atmega2560 to have a maximum possible resources (not only flash but also RAM)
Atmega1280 is pincompatible with atmega2560, so they are interchangeable.
Anyways, this is mainly playing around with KiCAD, and creating something that might be usefull along the road :). Design is not locked yet, so I'll take a couple of iterations on it (just like I did on the sensebender micro, with selecting powersource, and sensor types).
- w5100 SPI fix is already inside modern arduino ethernet shield http://www.arduino.cc/en/uploads/Main/arduino-ethernet-shield-06-schematic.pdf
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@axillent said:
@tbowmo thank! it is a good job done!
some questions/comments- w5100 SPI fix is already inside modern arduino ethernet shield http://www.arduino.cc/en/uploads/Main/arduino-ethernet-shield-06-schematic.pdf
do you think it is needed? what kind of the shield your are looking for?
I was looking at the cheap Chinese breakout boards with W5100 chip on, not all of them have the SPI fix onboard, so that's why I implemented it.
- why not to put 20MHz crystal to give some more performance to the gateway?
Hmmm.. think it was a price thing.. 16Mhz was more common than 20Mhz. But can't remember it right now (it's been a couple of weeks since I put in the 16Mhz xtal)
- USB is normally can supply not more than 500mA, are you sure it will be sufficient? DC-jack probably will be also good to have. ESP+wisnet could be hungry for the supply
In my thoughts, it should be either W5100 or ESP8266 mounted, not both at the same time (since both is for "internet" access. Also, most phone chargers are delivering 1A and up. Also, if you connect the thing to a computer via USB, you might not want to use W5100 / ESP8266 to communicate with it, so those power eaters could be left out in that case, leaving only NRF and/or RFM69 as radios.
- why atmega1284? it is not a standard arduino choice but could costs on a level of 1280. atmega128 is the lowest cost 128k AVR. If we are sure 128k will be sufficient in the future I will select atmega128 because of cost or atmega1280 because it is standard for arduino
There are some people that are using atmega1284 with arduino IDE, so it can be used. Solderability is the first reason: atmega1280 is 100pins, while atmega1284 is 44 pins, price: atmega1280 is 15.96$, while atmega1284 is 8-9$. Of course I can see the point in putting in 1280, as it could be swapped for a 2560 if more flash/ram is needed.
And also I will consider atmega2560 to have a maximum possible resources (not only flash but also RAM)
Atmega1280 is pincompatible with atmega2560, so they are interchangeable.
Anyways, this is mainly playing around with KiCAD, and creating something that might be usefull along the road :). Design is not locked yet, so I'll take a couple of iterations on it (just like I did on the sensebender micro, with selecting powersource, and sensor types).
@tbowmo 20mhz should cost very similar to 16mhz, price is not an issue in this choice. Frequency is one of the parameter you will need to put inside boards.txt, it could be no issue to replace 16 by 20
ok I see. if soldering is an issue there is also atmega1281/atmega2561 pin compatible having TQFP64 package while been fully compatible with atmega1280/2560 (they do have single datasheet). Their maximum xtal is 16mhz
sense and drive
- w5100 SPI fix is already inside modern arduino ethernet shield http://www.arduino.cc/en/uploads/Main/arduino-ethernet-shield-06-schematic.pdf
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@tbowmo 20mhz should cost very similar to 16mhz, price is not an issue in this choice. Frequency is one of the parameter you will need to put inside boards.txt, it could be no issue to replace 16 by 20
ok I see. if soldering is an issue there is also atmega1281/atmega2561 pin compatible having TQFP64 package while been fully compatible with atmega1280/2560 (they do have single datasheet). Their maximum xtal is 16mhz
As I said, I can't remember why I decided on the 16MHz crystal... it could have been a decision based on baudrate accuracy. But I'm not sure now.
one thought, is the arduino spi library capable of using the extra spi ports on the atmega1280? (The 4 uarts can be reconfigured as spi ports)
Started debating with myself, the benefits of changing cpu :) I'll look further at the data sheets.
