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Options for keyboard?

Keilaron

New member
So, I have a bit of a n00b question here:
Is USB the only option for a keyboard? I'm thinking of having a keyboard integrated in the casing for this module (provided I can get one of the last ones available), but I'm a bit hesitant due to the fact that as far as I know, my only other option would be to handcraft something that would (somehow?) use one of the serial ports on the expansion port.
Reason is I'd like to keep the USB port for other things like wifi. I suppose if I could find a special cable or keyboard it might come with a hub.. but I've only seen full-sized keyboards with those.
Any ideas/suggestions?
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Keilaron

New member
Thanks for the prompt reply, Rob.

I found the information about the pin-out and mating connector so I think hooking up something via serial shouldn't be too difficult provided I can find an actual serial keyboard of some sort...
The wireless operation video shows a 3.7v 3Ah LiPo battery attached to the CFA-910, but I'm not sure where this should be attached (electrically speaking), and the spec sheet doesn't specifically mention batteries. Also, what's the voltage tolerance?
 

CF Support

Administrator
Hi Keilaron,

The battery is an unsupported option. I can tell you how to hook it up be we cannot support it.

On the back of the CFA-910 there are 5 pads for a solder on battery.

SCL = I2C bus clk
SDA = I2C bus data
+ = LTC3576 BAT input
- = GND
TC = LTC3576 NTC thermistor input (battery heat sense)

You can connect a Lithium ION battery to the + and - lines. (You will need to either wire a thermistor (which should be against the battery) to TC or tie TC to ground otherwise the battery will not charge.)

The I2C bus that is brought out is the same bus the LTC3576 (main power controller) and the TPS65180 (TI E Ink power supply) are on. There is no battery management software configured for the I2C bus. (It would need to be configured or written for whatever you use for a battery controller or don't use a battery controller.) The LTC3576 does monitor the battery charging state and that is exposed in the LTC3576 driver. See: https://github.com/crystalfontz/linux-2.6/blob/cfa-10022-v0.3/drivers/i2c/chips/ltc3576.c

The LTC3576 datasheet will have more information of what batteries are supported.

--Rob
 

Keilaron

New member
Took me a bit to find what you were referring to, but I see it now on the bottom edge. OK, I think that makes sense, except wouldn't it be an issue if I connect something to the same I2C bus then? I2C is something I've not looked into much.

When you say "no battery management software", like what? Do you mean something that controls whether or not power needs to be sent to the battery? The LTC3576 doesn't help with this?

The datasheet seems to indicate the battery I may get will work just fine with this.
 

CF Support

Administrator
Hi Keilaron,

I2C is an addressed bus. Several devices can share the bus as long as they have different addresses. But anyway...

The I2C bus was brought out there for use with a battery gas gauge like a coulomb counter so there would be a method for determining how much battery life you have left. It could also be used to track charge cycles and things like that. The software to make use of it was not implemented. Some software for coulomb counters may be in the kernel for some chips. This is not a necessity; it was a planned enhancement.

The LTC3576 know how to charge the battery and can tell when it is full but cannot track energy in vs energy out.

--Rob
 

Keilaron

New member
On the subject of the thermistor, am I correct in thinking that a 100K thermistor would be what I need (my battery's datasheet says the operating temperature is 0~45°C)? Also, reading the datasheet for the LTC3576, I'm wondering if it can detect the presence of a bias resistor even if TC is wired to ground as it is currently telling me there's an NTC fault.
 
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