eList
The concept is the device sits on the charger and receives entries to the list using a wireless solution.
Entries can be added or subtracted using a web server application, that formats and transmits the list contents to the eLIST.
see the previous posts eLIST progress 2 , eLIST progress , eLIST - KOBO Touch , 5W Load Schematic
eLIST Detection
One of the parts of my challenge is to detect that the eLIST device is present.
This changes the webserver to signal to anyone trying to add items to the list, that they are too late, or that for some reason it won't accept them.
As delivered D5 (green) LED flashes when it detects a receiver or transferring power.
D7 (red) LED is used for Fault and FOD (Foreign Object Detection) and flashes if a metal object is detected.
Both LED's flash slow if the power is being limited.
The TX module has various options for the indications using the three LED's.
They allude to this in the SLVU928A.pdf however they don't give any proper information.
You need to seek the datasheet for the bq500212A and look on page 13, to find the table.
The standard value for R23 is 42.2k, which means it uses option 1.
I wish to avoid the flashing status, so I need to find another control option.
The first task is removing R23.
Its the tiny little smd next to JP2.
One end is attached to the rather large ground plane, and rather than destroy it, I used a soldering iron and the smd heated tweezer tip to remove it.
Since I didn't want to lose it, I rotated it 90 and soldered it back to the ground pad.
This now means I can add a resistor across JP2 will allow me to choose which Control Option suits my use.
Since this is designed as an evaluation board, I would have thought they would have made it easy by using a 3 position jumper or putting it in the earth end so you can insert another value easily.
The documentation is also poorly managed, they refer to LED 1,2,3 in the table, use LED_A, LED_B, LED_C in the chip datasheet, and call them D5, D7 and D9 on the evaluation board.
I do think Mr TI that you might need some document tidying. Having all the relevant information on the same paperwork as the kit would be a good starting point.
LED's
Part of Qi protocol is FOD detection, so I think it useful to warn the user and make it fairly clear by using the appropriate colour.
Despite having three LED's, IMO they aren't used very well.
Control 5, 6 and 7 are the only options using all three LED's.
Control 5 uses the red LED for Power Transfer, FOD and Dynamic power limiting, yet it only Blinks the amber for a Fault. Green is only used when the charging is complete. (which could be a signal for GO).
Control 6 is better and uses the red LED to show a Fault, and Flashes for FOD. The green is flashed while transferring and solid when charge complete.
If only they made the amber solid when transferring, I could have used it.
Control 7 makes better use of the amber by indicating Fault, Power limiting and FOD. The red LED is used to signal Charge complete, but it flashes the green when transferring.
Apart from the flashing, it could have been useful.
My control would look like this
Green shows normal, Amber is a warning, and Red is a fault condition.
Short of reprogramming the chip, I have chosen to use Control 5 (but I reserve the right to swap the amber and red LED's)
Charge Complete
Despite my best efforts to fool the system, I haven't been able to simulate a Charge Complete.
It's quite likely that the evaluation receiver, and my Asian universal receiver don't send the signal back to the transmitter, or that I'm missing something.
I can fault it by adding two receivers, and jiggling them to swap over during the charging.
Outputs
Now that I have two indications I want, I can extend the LED's and use them to control the RPi GPIO.
I prefer to isolate the signals, with either a transistor, or better still an opto-coupler.
Either method ensures no voltage greater than the supply is applied to the GPIO (inc when the RPi is off).
stay tuned
Mark
edit
My other posts Wireless Challenge .... Beer Tap (the other bit) - 4 Assembly Wireless Challenge .... Beer Tap (the other bit) -3 Wireless Challenge .... the other bit -2 Wireless Challenge .... the other bit Beyond the Phone - eLIST progress 4 (Transmitter modifications) eLIST progress 3 eLIST progress 2 , eLIST progress , eLIST - KOBO Touch , 5W Load Schematic