juiceme
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2013-10-24
, 19:41
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Community Council |
Posts: 4,920 |
Thanked: 12,867 times |
Joined on May 2012
@ Southerrn Finland
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#141
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2013-10-24
, 21:02
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Posts: 1,067 |
Thanked: 2,383 times |
Joined on Jan 2012
@ Finland
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#142
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2013-10-24
, 21:36
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Posts: 1,104 |
Thanked: 5,652 times |
Joined on Feb 2010
@ Holland
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#143
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2013-10-26
, 15:14
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Posts: 20 |
Thanked: 18 times |
Joined on Sep 2009
@ Valencia (Spain)
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#144
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Even the most low power microcontroller doesn't match even near the current consumption of the TCA8424 and like. With mobile devices energy preservation means everything.
And if I understand correctly, you don't have to use TCA8424 as I2C HID device, you can use it like any other I2C device. Just read the data after the interrupt line goes up.
I don't actually understand how using a microcontroller would be easier. You'd then have to write a custom driver for sailfish, which would be a same amount of trouble as writing a driver for TCA8424.
If the I2C HID driver appears to be too difficult task and custom driver is not tempting, e.g. ADP5588 has a linux driver available.
IMO using a microcontroller for this kind of task does not make sense.
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2013-10-26
, 19:14
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Posts: 986 |
Thanked: 1,526 times |
Joined on Jul 2010
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#145
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2013-10-26
, 20:32
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Posts: 65 |
Thanked: 56 times |
Joined on Oct 2013
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#146
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so ive been thinking about the n9's low-power-screen and seriously considering exploring an arduino lcd TOH, but i forgot that im obviously never going to use anything other than a keyboard other half.
which led me to thinking about a kb+lcd OH pipe dream. can anyone here comment on the feasibility of:
1) making an lcd OH at all, preferably 16x4 with backlight control. {i2c is way faster than LCD refresh rates, right?}
2) making a kb OH which when closed, would be disconnected, fully exposing the i2c interface and power for a generic addtl OH.
3) actually making a combined kb+lcd OH. is there sufficient bandwidth on i2c, sufficient power, etc? is it extremely unlikely that a microcontroller exists that can handle this? will the thickness be ridiculous? etc.
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2013-10-26
, 21:51
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Posts: 121 |
Thanked: 231 times |
Joined on Oct 2013
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#147
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Yes, I agree with the statement that a microcontroller requires more power. But I prepared some numbers and the results are interesting.
TCxxx requires only up to 70uA @ 3.3V 1 MHz. Very good.
Now, we can elect some ultra-low power microcontroller of the ARM Corte-M family.
For example, a bit old ST's STM32L100C6 that has 32KB of flash ROM and 4 KB of RAM, 2 I2C, DAC, ADC, USB, SPI, UART, RTC, LCD DRIVER, TOUCH SENSING, ...
http://www.st.com/web/en/catalog/mmc/FM141/SC1544
-Run mode @0.5MHz, 150 uA
-Assuming a well designed firmware, you can sleep the micro and awake for scanning the keyboard. I estimated around a rough 500 instructions for scanning completely the kbd.
-This is around 2 ms of work, including awake and return to sleep.
-Now, assume that you scan the kbd at 50 Hz rate. That is, every 20 ms.
-The remaining 18 ms (20-2), you can maintain the microcontroller in low-power mode.
-Low-power mode: 9 uA
-In average the requirements are: (2*150) + (18*9) = 23 uA
These numbers are only for the CPU. You need to add the current drain of the powered peripherals: I2C, GPIO, ... so I estimated around 200 uA of draining in the worst case. Excellent for the kind of power supply of a smartphone.
But you can do better thing. Put the micro in Stop mode and awake it when the keyboard is opened:
-Stop mode: 0.6 uA far better than the TCA.
In any case, I think the ST's micro is not adequate here, it'a a hell soldering it by hand.
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2013-10-26
, 22:13
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Posts: 20 |
Thanked: 18 times |
Joined on Sep 2009
@ Valencia (Spain)
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#148
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And you didn't answer my question. How does using a microcontroller ease the driver issue with Sailfish?
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2013-10-26
, 22:21
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Posts: 20 |
Thanked: 18 times |
Joined on Sep 2009
@ Valencia (Spain)
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#149
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Good luck trying to find a low power device in a bigger package. Those are quite uncommon in modern ICs and old ICs tend to consume more power.
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2013-10-26
, 22:26
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Community Council |
Posts: 4,920 |
Thanked: 12,867 times |
Joined on May 2012
@ Southerrn Finland
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#150
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Originally Posted by wolkeso ive been thinking about the n9's low-power-screen and seriously considering exploring an arduino lcd TOH, but i forgot that im obviously never going to use anything other than a keyboard other half.
which led me to thinking about a kb+lcd OH pipe dream. can anyone here comment on the feasibility of:
1) making an lcd OH at all, preferably 16x4 with backlight control. {i2c is way faster than LCD refresh rates, right?}
2) making a kb OH which when closed, would be disconnected, fully exposing the i2c interface and power for a generic addtl OH.
3) actually making a combined kb+lcd OH. is there sufficient bandwidth on i2c, sufficient power, etc? is it extremely unlikely that a microcontroller exists that can handle this? will the thickness be ridiculous? etc.
Although I have not followed this discussion about the OH keyboard, I got interested i the "LCD OH".
- What does an lcd OH comprise? Is there a 16-column / 4-row keyboard? (a virtual one?). What would its added value be?
- Why would an extra lcd be required in the OH, in addition to the touch screen of the Jolla phone? Do you mean that the lcd would display the text you enter (perhaps in a small frame like those which some Symbian smartphones of Nokia have)?