Minimal design thoughts
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I'm thinking about spinning up the good old eagle cad program again, and start creating sensor boards (Like so many others here :))
Only thing is, that unlike (almost) everyone else, that are using normal arduino micro boards, I'm thinking about skipping that part, and create my "own" arduino board, thinking about the following:
- use atmega 328 tqfp (That's doable for home soldering :))
- pads for a 32Khz crystal, for timing purposes
- Standard atmel programming header.
- ftdi header like on arduino mini, so could use arduino bootloader (could be some details about the baudrate though, as it's running off internal RC oscillator)
- Using Si7021 integrated humidity / temperature sensor, footprint for bmp180 barometric sensor
- skip power converters, run everything off a battery directly (disable brownout detection in atmel)
- SPI flash / e2prom onboard. Using same connections as moteino from lowpowerlabs, so should be able to use same bootloader for updates to firmware
- pinheader for connecting radio module
- Pinheader for D3-D7 on one side, and SDA/SCL + A0/A1 and power on the other side
- Formfactor is 30x17.5mm (almost same size as the NRF24 module).
- ATSHA204A sot23 footprint on board (Connected to A3). Can be used for SHA256 key exchange and verification
- status LED (on A2)
Any thoughts about this? Or should I wait for the all in one mysensors battery sensor board? (When will that be available?)
/ Thomas
(Spec updated January 28th, 2015)
@tbowmo Since Domoticz (home automation software) got support for MySensors i have been looking for cool sensors. I want to place a MySensor node in every room in my house with temp/humidity motion and reed contact, run directly from battery. Your board looks very promising. I only have one question. Is it possible to have two interrupts (for the motion sensor and reed contact)?
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@tbowmo Since Domoticz (home automation software) got support for MySensors i have been looking for cool sensors. I want to place a MySensor node in every room in my house with temp/humidity motion and reed contact, run directly from battery. Your board looks very promising. I only have one question. Is it possible to have two interrupts (for the motion sensor and reed contact)?
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What bootloader should I go for, for the prodcution run? (that is preload a bootloader into the atmega) ?
I am also thinking about preloading a default sketch as well, so it's almost plug'n'play.
(@hek, this default sketch should probably be included in the mysensors git repo, right ?)
/ Thomas
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Yep, a default sketch would be nice that reports temp/hum. Think it should be added to examples-folder like the others.
Would be fun to test the flash as well... Haven't seen @ToSa (the bootloader developer) around here for a while. Ideally a new bootloader should be adopted and MySensors library store bootloader update messages (in flash) at normal "runtime".
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I have been trying to get DualOptiboot from lowpowerlabs to run.. because it's able to use the external flash. It also seems like it is starting up as it flashes the LED during bootup, but it doesn't respond when I try to download via serial port using arduino. I might be blind or something, as I can't seem to figure out what the *beep' is going on :)
I have a sketch now, that is running on the first prototype here.. Should I make a pull request, to add it?
Btw. I have tested the external flash, by writing "random" bytes to it, and read it back again.. So I know it is working.
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I have been trying to get DualOptiboot from lowpowerlabs to run.. because it's able to use the external flash. It also seems like it is starting up as it flashes the LED during bootup, but it doesn't respond when I try to download via serial port using arduino. I might be blind or something, as I can't seem to figure out what the *beep' is going on :)
I have a sketch now, that is running on the first prototype here.. Should I make a pull request, to add it?
Btw. I have tested the external flash, by writing "random" bytes to it, and read it back again.. So I know it is working.
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I have been trying to get DualOptiboot from lowpowerlabs to run.. because it's able to use the external flash. It also seems like it is starting up as it flashes the LED during bootup, but it doesn't respond when I try to download via serial port using arduino. I might be blind or something, as I can't seem to figure out what the *beep' is going on :)
I have a sketch now, that is running on the first prototype here.. Should I make a pull request, to add it?
Btw. I have tested the external flash, by writing "random" bytes to it, and read it back again.. So I know it is working.
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@tbowmo
Regarding bootloader I stumbled upon this:
http://hallard.me/ulpnode-bootloader/
http://hallard.me/ulpnode-bootloader-1/ -
I don't have problems with bootloaders in general, I tried the standard arduino bootloader, and it works ok. It's just the DualOptiboot from lowpowerlab I can't get to work.. And it drives me crazy :)
Think I need to figure out some way of debugging the bugger, to figure out what it is doing, but it's hard to find time for it, when I only have one hour every now and then for debugging..
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I don't have problems with bootloaders in general, I tried the standard arduino bootloader, and it works ok. It's just the DualOptiboot from lowpowerlab I can't get to work.. And it drives me crazy :)
Think I need to figure out some way of debugging the bugger, to figure out what it is doing, but it's hard to find time for it, when I only have one hour every now and then for debugging..
@tbowmo yup, debugging these things is a pain in the neck - I've been working on the OTA bootloader for a while (mainly optimizing size, speed and additional features). What works best for me, is using debugwire in atmel studio...but sometimes quite cryptic and not straight forward :)
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@tbowmo yup, debugging these things is a pain in the neck - I've been working on the OTA bootloader for a while (mainly optimizing size, speed and additional features). What works best for me, is using debugwire in atmel studio...but sometimes quite cryptic and not straight forward :)
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Bugger.. DHL tried to deliver the package with PCB's from dirtypcbs, while I was at work today. So they only left me a note, that they couldn't deliver it. Have to wait untill monday, before they will try to deliver it again.. :s
Anyway, I now know that the boards are in DK somewhere :)
The other day I also have received 3 pcs of ATSHA204A (samples). so I can verify that part of the HW design.
And last but not least. I have a uCurrent waiting at the post office, that I can pick up later today.. So I can also start measuring supply currents to the device! :) Hope that I'll get some time to look at that part during the weekend :)
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Good news..
On a saturday evening, where nothing is on TV, but a danish pre- european song contest program, I decided that I should have a look at the bootloader (amongst other stuff)
I actually succeeded in getting the bootloader into the device, and I can reprogram using serial now. Next step is to verify that I can use the spi flash to reload the unit.
I have thought of a strategy for testing the flash for reprogramming. It involves making a very basic sketch that I could compile and put into another sketch, which writes the first one to the flash, and reboots the device, and thus reprograms itself with the first sketch :). But it's going to take a while for that to happen (if anyone have a better idea, then please let me know :))
I also have tried the uCurrent, and tried to do some measurements on current consumption. When it's a sleep, it uses arround 60uA, and while awake it's up to 22mA for 60m seconds.
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That current draw seems a bit high.
A modified 3.3V pro mini draws ~100nA in "deep" sleep without watchdog timer (pretty much everything disabled). The nrf24l01+ draws ~900nA in power down. If you wake up the 328 using its watchdog timer (i.e. sleep != 0), then that watchdog will draw around 5uA, but it wakes up every 8 sec, so the average "extra" current consumption caused by the watchdog is closer to 6uA. According to the si7021 datasheet* it draws 60 nA standby current, and 150 uA active current.
In other words, you should see a current consumption < 10uA in sleep mode. When active, the si7021 is negligible compared to the nrf and 328's current consumption, but the total consumption for nrf and 328 should still be less than 22mA... The 60ms you see probably indicates that the nrf is not able to get a hardware ("link-level") ACK, so it retries up to 15 times. Also, disabling DEBUG in MyConfig.h will save a few extra milliseconds. You should also make sure node.send() is the last thing you do before node.sleep(), or else the NRF will countinue to draw ~13mA until sleep() or RF24::powerDown() is called.This should not be too far from the theoretical current consumption profile for your board when reading hum+temp at given INTERVAL:
(Assuming the nrf, 328 and si7021 has already been "booted")sleep(INTERVAL): ~7uA on average
awake time 2+12+10.8+8 = 32.8ms
- 328 wakeup: 3.6mA for 2ms
- si7021 conversion hum: 3.6mA + 150uA for 12ms
- si7021 conversion temp: 3.6mA + 150uA for 10.8ms
- nrf24 send: 3.6mA + 13.4mA for 8ms (assuming no message retries)What components are actually mounted on the board you tested?
The ATSHA204 should draw max 3mA active, and <150nA sleeping.
The 25aa080sn*- Write current: 3 mA maximum
- Read current: 500uA typical
- Standby current: 500 nA typical
You probably already know all this, but I thought I might mention it anyway :)
http://www.silabs.com/Support Documents/TechnicalDocs/Si7021.pdf
http://www.atmel.com/Images/Atmel-8740-CryptoAuth-ATSHA204-Datasheet.pdf
http://ww1.microchip.com/downloads/en/DeviceDoc/21230E.pdf -
I haven't done anything to optimise things yet. The sketch I'm running is in the examples section on Mysensors github repro so you could have a look there.
The board is without external flash (didn't mount it on board #1 that i used last night) and without atsha204, as it's still the first prototype board. The new version should arrive tomorrow, where I can mount the atsha204.
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forgot an update last week, I received rev2 boards last monday (9/2). but was on vacation with the family (They have priority above "nerd" projects ;))
Will see if I can get a couple of pictures of the new boards when I get home from daytime job today.
And hopefully, I'll get a couple of boards mounted during this week, so I can get it verified, and we can start preparing for "production to the masses" :)
