imac4567

That text is in the Rockwell datasheet. Its on page 2! Wow I feel really stupid right now , I was reading the second part of the I/O ports . -Dylan

Oh, I was looking at the rockwell datasheet one, not the other one. My bad -Dylan

PA7 was probably a bad example. The answer is in the first 12 lines of the section entitled "I/O PORTS (PA0-PA7,PB0-PB7)" in the RIOT datasheet. You don't need to look anywhere else!! Well when you said PA7 it just popped into my mind, anyway if your talking about in general well when its made an input when it is read directly from the pin and transferred to the processor as the same for the DRA as long as the pin is allowed to go to 2.4V. The processor also writes directly in the corresponding bit. -Dylan sorry but I don't have a resistance meter, my step dad might have one but I am at my real dads right now.2. answer The threshold volts should be(after doing the equation) 3.4042V. 1. Answer neither b/c a resistor is not active to bring it high or low, right? -Dylan

Nope! That conflicts with what you said in the previous post which was correct. The answer really is in that section of the datasheet. I'll give you a specific example... What else happens inside RIOT at port bit PA7 if that port bit is made an input? When the port bit PA7 is made an input it is also is an edge detecting input and sets an internal interrupt flag. If its set then it makes the IRQ output lower. -Dylan

Getting warmer! Its half an answer tho. Something else happens too, specifically when a port bit is an input. You'll kick yourself when you get it. OK got updated schematic up \/. I believe a port bit is specifically an input when the DDRA is programmed with a logic one or zero, in which zero is input. Hope its right. Untitled_15.jpg.zip -Dylan

Alright this should be the right answer, when a logic zero bit of the A port DDRA, well that is what causes the A port bit to act as an input. And a logic 1 causes it to act as an output -Dylan

Yep! You read the Data Register to read the logic levels on the external pins. However it doesn't explain why they are pulled up. I'll lead you a bit closer... What happens when you write a '0' to a port bit in the Data Direction Register (DDR)? When the Data Register Reads 0 it means that there is no input on one of the 8 lines and if there is a 1 is reads it as an input. Well I think I am getting so close I can smell it . Not quite! The Data Direction Register A (DDRA) controls the direction e.g input/ouput of the Port A bits. When you write '0' to a bit in register DDRA it makes that particular Port A bit an input. Re-read the section and tell me what else happens when you do that. Still reading it what I said before was not right I new it When you do that also the processor is writing to the corresponding bit of the DRA -Dylan

Yep! You read the Data Register to read the logic levels on the external pins. However it doesn't explain why they are pulled up. I'll lead you a bit closer... What happens when you write a '0' to a port bit in the Data Direction Register (DDR)? When the Data Register Reads 0 it means that there is no input on one of the 8 lines and if there is a 1 is reads it as an input. Well I think I am getting so close I can smell it . Not quite! The Data Direction Register A (DDRA) controls the direction e.g input/ouput of the Port A bits. When you write '0' to a bit in register DDRA it makes that particular Port A bit an input. Re-read the section and tell me what else happens when you do that. Still reading it what I said before was not right I new it

Yep! You read the Data Register to read the logic levels on the external pins. However it doesn't explain why they are pulled up. I'll lead you a bit closer... What happens when you write a '0' to a port bit in the Data Direction Register (DDR)? When the Data Register Reads 0 it means that there is no input on one of the 8 lines and if there is a 1 is reads it as an input. Well I think I am getting so close I can smell it . -Dylan

Yep! From the Wiki article. Eureka! After further reading in the article and data sheet I found that the Data Register pulls up b/c bits that are transferred to the processor are transferred to the DR also there by pulling bits up w/o changing their polarity -Dylan BTW: I thought I saw a not RIOT instead of in RIOT Datasheet

I men't that too, kinda. but its on the same page as the other one right?

Yep! Well... Nearly but I'll give it to you . The switches provide the pull downs to RIOT on PortA not PortB. So you need pull ups and there aren't any in the Atari schematic. So where are they? The answer is in the RIOT data sheet (in the section I mentioned in the original thread)... Its http://www.national.com/mpf/LM/LM339.html"]here[/url] or http://www.allaboutcircuits.com/vol_3/chpt_8/3.html"]here[/url] right?

I hate my mouse [] [] \/

Thats fine with me, even so it may be boring as hell to them but its learning to me . Will PM for the rest of PSP to Atari 101. -Dylan

ok Im reading as of now I'm finally getting this riot chip! The Joysticks are pulled up and down by peripheral data ports on the RIOT and are programed to react when there is a change in voltage using input mode. When its input mode the outputs are in the 1 state then pull-up devices such as the joystick acts as "less" than one TTL or Transistor–transistor logic loads to the peripheral data lines. The perphieal lines are all ttl compatible and will read correct info as long as 1s are greater than 2V and 0s are less than 0.8V

ok Im reading as of now

What riot datasheet, oh are you talking about this one LM139.pdf

I see a 10K resistor but that is pin 6 which is only the Fire Button resistor and that is all that I see, but I do have a theory doesn't the ground have something to do with how it pulls up and down or makes it respond? -Dylan

Not exactly. You need to understand what the Atari does and work with it, not against it. Check the Atari schematic to see if there are pull up resistors fitted to the direction input pins. If there are then note down the value, locate them on the PCB and double check their value with your multimeter to make sure. If there are pull down resistors, what does that mean to your circuit design? You need pull up resistors on the outputs of the LM339 opamps not their inputs. Have a look at the equivalent circuit for one comparator opamp in the National LM339 data sheet (its on page 15). You'll see that its an opamp with its o/p connected to the base of an NPN transistor Q7 (used as an inverter). The collector of Q7 is connected to the base of NPN transistor Q8. What do you notice about that part of the circuit? Especially the collector? Do you know any transistor theory? Read up on open collector. Yep! I know it would be much easier if I just gave you the circuit. But its important to understand why you do things. Then when you come to to do it again for another project but the situation is slightly different you'll be able to handle it by applying theory and not by having learnt something parrot fashion (which will probably fail). Well I did take a look at the atari schematic and board and I see 4 capacitors that the joystick wires go through before they get into the 4x4 square 2(that are the up and down wires) have .001Z Z5P and 2(left and right) that just has the number 102 which I believe is .001uF. They both are the same value I think so they all pull down not up, correct? But if the capacitors are all the same value how do I get a pull up resistor. I'm asking all of this before update the schematic so I know I am doing it right. Thanks -Dylan

I'm pretty damn sure that he knows about Ben Heck. Just because he was the first (1999) doesn't mean he should stop making his portable. That's like saying there is no use in making the gameboy because the Microvision beat it to the market. Way to try to take the wind out of his sails. Just another quality post from McJakeQCool Yah, it really doesn't matter. And the first was actually Kevin Horton in the mid 90's anyways. He did a lot of other firsts as well (first Colecovision homebrew, Kevtris, done without any documentation - just reverse engineering and assembly coding). Here's his old projects page. Ben and him actually had a brief project together back in 2001 called the Phoneix which was a portable 2600 with a custom pcb. I have actually seen one with a custom PCB Here , pretty cool but looks like it would be a pain to get everything up and running on the new board. -Dylan

DANG My mouse button is touchy [] [] \/

So do I just need to add a 10K resistor to the input Vs on everything? And put the threasholds like the ones on page 2 that you stated and I am mostly done after the 9 D thing? -Dylan

Dang 2AM its 9:11 PM here Can you explain the theory of operation? As I'm seeing it, it isn't going to do what I think you think it's going to do. well if you look on page 2 and 1, I am trying to get a psp joystick to work one my vcsp instead of a ps1 stick b/c the psp will make the vcsp be able to be smaller. That is what I am doing, Thanks for your interest ! -Dylan I understand what you're trying to do. Note that I quoted the drawing. I was asking you to explain how that op amp circuit will work. I can't really explain it at the moment, my brain rushing faster than a race horse , in the past 6 hrs I have learned what op-amps were, how to make a circuit (the right way), added to my library of ICs, and just others things that are hard to explain. When I get this thing done I will give you a brief summary. Thanks -Dylan

I will get it in a little bit, right now I am wiien it up but I will upload in a few -Dylan

Can you explain the theory of operation? As I'm seeing it, it isn't going to do what I think you think it's going to do. well if you look on page 2 and 1, I am trying to get a psp joystick to work one my vcsp instead of a ps1 stick b/c the psp will make the vcsp be able to be smaller. That is what I am doing, Thanks for your interest ! -Dylan