Ööö . IRDA is serial comms over infrared (RX/TX), afaik N900 is/was only capable of transmitting IR (like with Irreco app)

Hmm... Using just the UART to send IR 'bits' with carrier frequency could be possible. The carrier is about 30...60 kHz, say 40kHz. If this is set to uart bitrate.
The actual datarate is way much lower, say something like 1200 bps. So we need send about 4 bytes of 0xAA for one high bit (and 4 bytes of 0x00 for one low bit (hoping that the STOP bit doesn't cause problems)

Doing it like this would free the phone cpu from low-level timing and lets the uart to do it. just feed the data to fifo over i2c.

Could be doable. Just add buffer and IR led there.
For IRDA something like TFBS4711 could be suitable.

Why not use a dedicated IRDA chip, with an I2C interface then ?
Something like this : http://www.nxp.com/products/interfac..._gpio_bridges/

Would solve problems like the stop bit.

By the way this chip seems to also provide RS232/485 interface and GPIO.

Project is already using the SC16IS850L

There is no problem with the IRDA, it will work.

The idea here was to use the IRDA transmitter to mimic the e.g. TV remote control by making the ~40kHz (or 38kHz) carrier signal with bit pattern.
https://learn.sparkfun.com/tutorials...munication/all
and something here
http://youtu.be/BUvFGTxZBG8

exactly, main purpose, for me at least
Oh and, yes, I know the N900 have irda that was my point. No of the devices i have had since that have had irda interface. So, even better if we can combine this with rs232 as well - and - that OLED / perfect device!

My bad... as I didn't remembered you talking of IRDA out before on this topic, I assumed the chip you selected didn't have IRDA and didn't check the previous page...

Thanks for the link. I think I understand now.

Wouldn't the proper way to do this be that the chip is configured with the expected 1200 bauds and modulate it after (with an ne555 like or an I2C PWM expander if its period needs to be software controlled).
This would reduce the I2C load (probably not a problem anyway), and remove the need for some bit conversions to send data, so something like "cat /dev/xxx" would allow to see directly the received value (and not a list of 0x0 or 0xF for each individual bit) ?

Your solution work, but I always tend to choose hardware when possible to avoid doing tricky stuff in software.

Edit : After second though, there may be problems with the start/stop bits with this proposal. Don't know if they are the same on IR than with say a RS232 line, so that the UART would understand them correctly ?

That is one possiblity... but i like to do things inside-out... (or atleast try)

no intention to receive "remote control" data here, just transmit.
transmit can be done to work like echo "123" > mytransmitthingy with piece of software.

In sending bit '1' there is no problem with start/stop's, but when sending '0', the stop bit gives a pulse of half period of 38kHz every 10th period of that. Hopefully that is filtered out by the IR receiver.
One possibility is to stop transmitting at all when '0' but to get proper timing is pain.

uf... ....

Stupid question... What would be the best direction of IR ?

This affects the PCB design.

• A = USB connector direction (i think it is this)
• B = Where the camera points
• C = Left
• D = Right

The transceiver can be mounted in top view or side view, so the option B will be possible with any other option.

Option B only will make smallest PCB area.
With option A, have to go around the camera...

B would be no option in my opinion. if you think of the theoretically possibilities like playing with a joystick you can't put the phone on a table without any special mounting.
Also I would consider it only if it would shrink into the OH (unlike your render) that would result in a really thick OH.

How would a construction of A/C/D look like? You also would have to have an OH thickness as wide as the R232 or your OH go around the phone on all- or only the upper side(s). Did you think of this idea?

One more effect to consider is the one on the bags for jolla. The only possibility to maybe not break every already existing bag is A. Then only the thickness can still be the problem.
Thats the reason A would be the one I vote for.

Mentioned before and now asked for all options. Are you planning to shrink it into the OH or put it on top?

this was mainly about the Infrared direction... i have not considered yet the D9 Direction yet. maybe it will be facing to dir A or towards you. display direction. making phone little longer