SparkFun PSP Touchscreen and Data Entry

[mypspdev]

Good morning,
I saw, starting search on this forum, the
http://www.sparkfun.com/commerce/produc ... ts_id=8448
SparkFun Touchscreen for PSP.
I'm assuming, but probably I'm wrong, that these devices are transmitting via serial signals their data, in this case something related with x and y of single touch on screen.
I saw also, again from this encyclopedic forum, the
http://www.sparkfun.com/commerce/produc ... cts_id=449
that connected to the HRPM plug using
Vcc - yellow
Gnd - blue
Tx - gray
Rx - orange
from a cut off remote cable (according to user "dsn" experience), it should work properly as Serial interface controller for PSP.
If my assumption of serial signal from Touchscreen, these two devices are enough to work finally with a new data input way for PSP.
I'm goiung to order both, anybody could confirm my (hope right) design and/or have experience on that issue?

Thanks in advance

[cory1492]

You'll have to look further for more touchscreen hardware, as far as I know no analog pressure data comes out of a plain touchscreen in serial without a controller/resistance interpreter of some type added.

I have that exact serial adapter here, it indeed works well for SIO use like the kprintf handler, psplink and perhaps other things that would support serial through the headphone port. It cannot get the highest speed the port is capable of though (too low voltage from what I was told to support 19,600bps), so a Max rs232 converter would be preferred for best performance.

[mypspdev]

You'll have to look further for more touchscreen hardware, as far as I know no analog pressure data comes out of a plain touchscreen in serial without a controller/resistance interpreter of some type added.

I have that exact serial adapter here, it indeed works well for SIO use like the kprintf handler, psplink and perhaps other things that would support serial through the headphone port. It cannot get the highest speed the port is capable of though (too low voltage from what I was told to support 19,600bps), so a Max rs232 converter would be preferred for best performance.

Thanks very much, my doubt was on my too easy assumption.

Please could you explai what do you mean when saying "I have that exact serial adpter here ..." .. is it the MAX rs232 converter?
May be we have to refer to http://nil.rpc1.org/psp/remote.html
Isn't it? Thanks

[hlide]

I'm assuming, but probably I'm wrong, that these devices are transmitting via serial signals their data, in this case something related with x and y of single touch on screen.

my assumption is that you're wrong. According to what we can read about those 4 wires in http://www.sparkfun.com/datasheets/LCD/ ... FD52-R.pdf, thoses 4 lines are not serial. there are X1, Y1, X2 and Y2.

So you probably need another piece of hardware with an MCU which would translate or embed your X1, Y1, X2, Y2 coordinates in a serial packet readable by PSP. I strongly suspect those lines to be analogic so you need a MCU with 4 ADC pins.

MCU : Micro Controler Unit (a small CPU with some stuffs like sio, spi, i2c, adc, dac, pwm, dmac, etc. integrated)

ADC : Analogic to Digital Converter

I would be glad to see this project to exist and work.

[mypspdev]

MCU : Micro Controler Unit (a small CPU with some stuffs like sio, spi, i2c, adc, dac, pwm, dmac, etc. integrated)

ADC : Analogic to Digital Converter

Now it sounds better, I've asked to spurkfun a final electric schema for doing it feasible and running, may be in their interest if they would like to sell it.

[memon]

Start with this and you should get your Google keywords right:

http://www.national.com/mpf/LM/LM8500.html

"Four Wire Resistive Touchscreen Controller" gets you pretty far :) I'm sure there are some example hobbyist projects around too.

[hlide]

Start with this and you should get your Google keywords right:

http://www.national.com/mpf/LM/LM8500.html

"Four Wire Resistive Touchscreen Controller" gets you pretty far :) I'm sure there are some example hobbyist projects around too.

this is better !

[mypspdev]

http://www.national.com/mpf/LM/LM8500.html

this is better !

So, final hardware required:

- qty 1 Sparkfun #LCD-08448 Touch Screen 4 wire resistive
- qty 1 LM8500 - 4 wire resistive touchscreen controller
- qty 1 MAX3232CPE - RS232 Serial Line converter
- qty 5 0,1 microF Ceramic Capacitors
- package

Connection schema:
Touchscreen 4 wire -> LM8500 -> MAX3232CPE
According to signals.

Is it all we need?

Ok...... starting ...... with part order.... thanks to all

[hlide]

http://www.national.com/mpf/LM/LM8500.html

this is better !

So, final hardware required:

- qty 1 Sparkfun #LCD-08448 Touch Screen 4 wire resistive
- qty 1 LM8500 - 4 wire resistive touchscreen controller
- qty 1 MAX3232CPE - RS232 Serial Line converter
- qty 5 0,1 microF Ceramic Capacitors
- package

Connection schema:
Touchscreen 4 wire -> LM8500 -> MAX3232CPE
According to signals.

Is it all we need?

Ok...... starting ...... with part order.... thanks to all

if you take a LM8500, why do you need MAX3232CPE ? since Vcc= 5,5V (CKI = 10 MHz) for LM8500.

you need a crystal clock too (10 MHz)

[Art]

The guy who told you that doesn't know what he's selling if you've relayed
what they told you right :D

The minimun hardware requirement to connect that touchscreen to the PSP is nothing
as I said in another thread, you could remove the analogue nub and connect it there,
but I don't think there's an easy way to make that loook good.

To connect it via serial you'd need something like a pic microcontroller with two
analogue inputs to read the state of the two potentiometers in real time and
transmit the position via serial straight to the PSP.
Like hlide said, but that's only two analogue channels (X & Y) not four.

A simple programming trick allows you to transmit from an pic to the PSP
without any RS232 converter by inverting the signal in software.
the serial line was never RS232 that's for takling with desktops.

[shsanjp]

Hi guys,

I too am interested in the Touchscreen. I have already purchased it and I am planning to hook it via a ATMEGA32 that I had lying around.

Atmel provides some sample code to drive the Touch Screen and a document describing how to hook it up. So it should be fairly straight foward.

http://www.atmel.com/dyn/products/app_n ... rt_id=3302
( AVR341: Four and five-wire Touch screen Controller )

I will have to take the power from the usb and plug it to the SIO too which is a bit ugly but unavoidable since the ATMEGA part that I have requires 5V.

My question is not really hardware related but on the software side.

I am currently modifying a Kanji Learning software and adding the touch screen will greatly improve it.
I'll probably do my first tests in that software with some dedicated code, but how easy would it be to produce a module which replaces the analog stick?

My guess is that it will have to be a rewritten prx or something permanently residing in memory at the kernel level to be supported by most software.

Apart the obvious issue of the analog stick to be 8bit values and the screen producing 10bit coordinates, I was also wondering if we could emulate the buttons (by clicking on some parts of the screen for example), although it might not be responsive enough.

Oh and by the way, assembling the touch screen is going to be messy (well a bit), obviously you cannot put it in the PSP but sticking it above the screen will require cutting a bit the buttons (> and square) because the screen is slightly too large.

[cory1492]

Please could you explai what do you mean when saying "I have that exact serial adpter here ..."

http://www.sparkfun.com/commerce/produc ... cts_id=449

[memon]

IIRC PSP operates on 3.3v, so unless you want to use external power supply, the LM8500 is out of the question. LM8300 is 3.5v model, might work fine with 3.3v too. Some other controllers operating at 3.3v:

Texas Instrument's TSC2005 is another one too:
http://focus.ti.com/lit/ds/sbas379a/sbas379a.pdf

Here's someone's project using TI ADS7843:
http://instruct1.cit.cornell.edu/course ... /index.htm
http://focus.ti.com/lit/ds/symlink/ads7843.pdf

Microcontrollers are also a possibility, but these controllers will just do the same thing and usually provide easier HW to interface with. As an added bonus, you can use the extra ADC inputs to measure temperature :)

[Art]

The Texas Instruments device you mention there has SPI interface that's a
proprietry connector like I2C (Inter-Intergrated Circuit Interface - the coolest acronym ever made),
the serial line has a seperate clock signal not compatible with the PSP.
http://en.wikipedia.org/wiki/Serial_Per ... erface_Bus
Now that you need a microcontroller to interpret the SPI output,
you might as well throw away the Texas Instrument device and just use the
microcontroller alone to interpret the input from the touch screen as well.

[shsanjp]

Just a quick message to say to ignore my previous question.

I have found the answer.
Thanks Tyranid for RemoteJoy ;-)

Now I just need to buy the few missing components and I am good to go.