Rockbox Development > New Ports
Rockbox Player - Project to design and build a Free/Open hardware audio player
spark:
hi people,
lots of development happened since i last wrote. i have a few suggestions
keyboard interface
8 lines for 8 keys is too much of wiring. since we already have I2C running to the expansion board it would make sense to use a an I2C I/O expander with interrupt support for keys.
e.g. PCA8574 for 8 I/O lines or PCA8575 for 16 I/O lines
PCA8574 -> http://www.rockbox.org/twiki/bin/viewfile/Main/RockboxPlayerV1?rev=1;filename=PCF8574_4.pdf
PCA8575 -> http://www.rockbox.org/twiki/bin/viewfile/Main/RockboxPlayerV1?rev=1;filename=PCF8575_3.pdf
power on/off logic
We need to add a separate power on button that controls power ON logic of power supply.
LCD interface
there should be an I/O line to control LCD backlight. If we use carrier board we have only one 3.3V supply line for both backlight and logic. This means that we will have to switch this supply line on/off to save power. LCD will have to be re-initialized on each power off/on cycle.
we can use a P-channel MOSFET to control LCD power.
again the above I2C i/o expander can be used for LCD power line (i.e. gate of P-channel switch).
anybody knows how much current the LCD module needs? i guess we can safely use a 500mA power switch.
casainho:
Spark, I wrote on TWiki the objectives for this V1 and the planing future versions. I hope they make sense, more or less.
--- Quote from: spark on January 26, 2008, 12:29:46 PM ---keyboard interface
8 lines for 8 keys is too much of wiring.
--- End quote ---
Adding another IC seems unnecessary to me, since we have free I/O lines on MCU (with pull-ups).
--- Quote from: spark on January 26, 2008, 12:29:46 PM ---LCD interface
This means that we will have to switch this supply line on/off to save power.
--- End quote ---
There in no need to save power, we are using a dev board. Future circuit on V2 can be totally different in question of this LCD and power circuit.
Your concerns looks like more for the V2 and not for this V1. If we go with Olimex for V2, looks like they will not need our help to design the circuit, however we will have to control that! On that time, I think that this ideas you wrote, can be worked, but not in this V1.
Look, I asked you in past to make a planing, you didn't and I had free time and I am being working on the project, I made the planing, contacts, and defined some simple hardware, I hope all this make sense and are ok.....
spark:
Casainho, i was tied up with something and could not write anything this week.
my concerns were for a basic player.
there should be a way to turn off LCD backlight if there is no user activity for certain time. (irrespective if we power from mains or battery). This functionality can be added by using a transistor (less than $0.5).
while development you should have free i/o lines. you never know when you would need them. the I2C i/o expander is a standard chip for less than $1.5
since we are already making an expansion board, i don't think adding these 2 chips is gonna cost a lot.
dev board
Casainho, did you get a user guide with the dev board? can you please upload it for us?
how does it bootload? u-boot in flash?
what if u-boot is erased? how do we recover a virgin board?
casainho:
--- Quote from: spark on January 26, 2008, 02:52:45 PM ---there should be a way to turn off LCD backlight if there is no user activity for certain time. (irrespective if we power from mains or battery). This functionality can be added by using a transistor (less than $0.5).
--- End quote ---
But If we will use this prototype just to show Rockbox working, we don't need all the little things. If we add that functions in hardware, they will also must be done in software, and for V1 there is no need, V1 will be just a straightforward version in terms of hardware + software.
I don't pretend to perfect all software for this V1, since just the developers will use this V1. And we have a lot of working ahead to do, in software!!
--- Quote from: spark on January 26, 2008, 02:52:45 PM ---while development you should have free i/o lines. you never know when you would need them. the I2C i/o expander is a standard chip for less than $1.5
--- End quote ---
Thats right, we can use this dev board for future development of another hardware, but, I am not seeing that possibility in a short time, because we already have all that we need in the board! There is no software in Rockbox for any other fancy hardware...
Even If we change the hardware a bit, we can draw a total new version of this secondary board.
--- Quote from: spark on January 26, 2008, 02:52:45 PM ---since we are already making an expansion board, i don't think adding these 2 chips is gonna cost a lot.
--- End quote ---
It's not a question of price for me, It's just I think we don't need or will need them, thinking in make a simple demo of this player, I think in simplifying the hardware + software + documentation + BOM, we will win time and this 2 things will change for sure quickly in the next version V2, they are just temporary.
--- Quote from: spark on January 26, 2008, 02:52:45 PM ---dev board
Casainho, did you get a user guide with the dev board? can you please upload it for us?
--- End quote ---
No, but looking at others manuals from Olimex, that manual should just be important for install Linux on the board, IMO. So I am not worried with that, since we have all information, all datasheets :-)
Bagder:
--- Quote from: spark on January 26, 2008, 02:52:45 PM ---there should be a way to turn off LCD backlight if there is no user activity for certain time. (irrespective if we power from mains or battery). This functionality can be added by using a transistor (less than $0.5).
--- End quote ---
This sort of stuff is already done by Rockbox. No need to do anything about it hw-wise really.
--- Quote ---what if u-boot is erased? how do we recover a virgin board?
--- End quote ---
The at91 chips are easily bootstrapped over serial (or usb I believe) even when nothing at all is in flash.
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