Mares Puck PC Cable
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Bryscus
Registered
A quick follow-up to my previous post with the schematic. The Schmitt Trigger NAND gate chip should be powered by the CP2102 board at around 3.3 volts (the CP2102 board should have connections for power, gnd, tx and rx at least). The grounds between the NAND chip and CP2102 board should also be connected together.
Theory of Operation:
1. When the Puck is either not connected or not in PC mode, the green light will be on. This is because the Puck tri-states (lets float) its DIO pin. Without anything to pull the DIO pin high, the 100k resistor pulls the NAND inputs low (pins 1 and 2) which then drive pin 7 high. If the Drak is not in SUSPEND (sleeping or not enumerated on the USB) then pin 12 of the CP2102 will be low which causes current to flow through the green LED, lighting it.
2. When the Puck is connected and put into PC mode, then the DIO pin is pulled high. This pulls NAND inputs high which causes pin 7 to be pulled low. This lights the red LED because current now flows from CP2102 pin 11 to pin 7 through the LED.
3. The PC then sends a message to the Puck. Pin 26 is pulled high normally (its idle state) which allows DIO to be pulled high. When Pin 26 is pulled low (when sending data), current flows through the S7 diode pulling the DIO pin low (to about the forward voltage of the diode).
4. When receiving data, pin 26 stays high, and DIO is toggled by the Puck computer. When DIO is high, pin 7 is low and pin 5 is idling high. This makes pin 25 high. When DIO is pulled low by the Puck, pin 7 (pin 6) is high and because pin 5 is also high pin 25 is toggled low.
This setup uses TX pin 26 as a switch for bi-directional data transfer - when held high, RX can receive. When data is sent and received the LEDs should flash from green to red based on the current state of the DIO line. This circuit also creates something like an open collector connection between the two devices. The data transfer speed is 38400 baud. I'm not sure if just using an open-collector output tied to the RX line would work. The PC would then have a loop-back where it received everything it sent. This depends on the computer software and what it does with the extra data.
- Bryce
Theory of Operation:
1. When the Puck is either not connected or not in PC mode, the green light will be on. This is because the Puck tri-states (lets float) its DIO pin. Without anything to pull the DIO pin high, the 100k resistor pulls the NAND inputs low (pins 1 and 2) which then drive pin 7 high. If the Drak is not in SUSPEND (sleeping or not enumerated on the USB) then pin 12 of the CP2102 will be low which causes current to flow through the green LED, lighting it.
2. When the Puck is connected and put into PC mode, then the DIO pin is pulled high. This pulls NAND inputs high which causes pin 7 to be pulled low. This lights the red LED because current now flows from CP2102 pin 11 to pin 7 through the LED.
3. The PC then sends a message to the Puck. Pin 26 is pulled high normally (its idle state) which allows DIO to be pulled high. When Pin 26 is pulled low (when sending data), current flows through the S7 diode pulling the DIO pin low (to about the forward voltage of the diode).
4. When receiving data, pin 26 stays high, and DIO is toggled by the Puck computer. When DIO is high, pin 7 is low and pin 5 is idling high. This makes pin 25 high. When DIO is pulled low by the Puck, pin 7 (pin 6) is high and because pin 5 is also high pin 25 is toggled low.
This setup uses TX pin 26 as a switch for bi-directional data transfer - when held high, RX can receive. When data is sent and received the LEDs should flash from green to red based on the current state of the DIO line. This circuit also creates something like an open collector connection between the two devices. The data transfer speed is 38400 baud. I'm not sure if just using an open-collector output tied to the RX line would work. The PC would then have a loop-back where it received everything it sent. This depends on the computer software and what it does with the extra data.
- Bryce
buton
Contributor
this is interesting, i knwo about this electronics i can build a pc board and i can send it to you, similar to the diveduino baord..
Will this work just by adding the Schmitt Trigger NAND, the resistors and diodes ?:
https://www.sparkfun.com/products/9873
also i am curious if this cable will work with this
http://www.divesoftware.org/libdc/
with the cable we can make some reverse engineering to see the serial bytes and commands the software is sending to grab the data in a simple txt file and then make what ever you want..
---------- Post Merged at 01:18 PM ---------- Previous Post was at 11:08 AM ----------
so after some research, check this out..
i think thats how it works in all computers just with two terminals
http://electronics.stackexchange.co...-uart-communication-between-2-mcu-over-1-line
all one wire with a reverse diode.....
i will try it...
DazedAndConfuzed
Contributor
group buy from whomever want to build a whole bunch of them?
Slamfire
Contributor
Depending on final price, I'd join a group buy. I had the an original factory cable/connector that mysteriously disappeared from my house. I've been looking all over but cannot find it. Right now I'm entirely dependent on my Shearwater Predator bluetooth connection for getting dive data into my pc.
buton
Contributor
I just bought the components, hope to build it during the weekend...
Bryscus
Registered
buton,
- The Mares dive software doesn't really care what type of device is connected to it since you can train the software to find whatever COM port the dive computer is on. Assuming the drivers are installed for a USB to serial converter, theoretically any converter would work. Thus, the FTDI one from sparkfun should work fine.
- As for using it with libdc, this is a possibility, but I'm not sure. I don't have any familiarity with libdc, but it's pretty cool I must say. You might even be able to pull the commands from the libdc source code for the Mares computers.
- I looked a your post a little while back when there were pictures on the site (for some reason they are gone now) but I think I remember the basic operation of the circuit they're discussing. That specific circuit would echo characters back as they were being sent from the PC. The circuit that Mares uses does not allow an echo back to the PC when it sends characters. Therefore, it's possible that this new circuit could work, but it requires that the Mares software ignore any data echoed back. My gut feeling is that this would confuse the Mares software, but I can't be sure.
I had to send my computer out for repair for unrelated issues and should be getting it back soon. I will then be able to test out the circuit I've described in previous posts. Please let me know if you get it to work on your end! Thanks.
- Bryce
DukeAMO
Contributor
I'd go in on a group buy, if I don't get the expensive one for Christmas, and if you can make them cheaply and still have it be worth your time and effort. I have the Mares Puck (not the newer Pro model). On my end, I have to consider the fact that it might not work. I'd risk $20-30 if you're pretty sure it won't fry my computers (or me)!
Bryscus
Registered
Duke,
I can say that at the moment I don't plan on selling these. After extensive searching on the web, I noticed that there was some information for other dive computers but none for the puck so I thought I'd add my two cents. After finally breaking down and buying the expensive cable I figured I would do a service to those who were in my position of trying to find DIY information. I know there are plenty of people out there with DIY skills and therefore am just content to the data I currently have. If there are others out there that would like to take on a project like this, I'm all for it.
- Bryce
wrenchmonkey
Registered
Has anybody been able to confirm that this works? Santa Clause brought me a Mares puck, and I don't really want to drop $90+shipping on a stupid interface cable that should have come with the thing in the first place.
Anybody able to confirm that this schematic would be functional? Any idea how to make connectors that would plug into the pick itself? (This is the air integrated console model, not the wrist model).
Thanks!
---------- Post added December 27th, 2012 at 12:45 AM ----------
OK, nobody ever accused me of being too patient. I ordered enough parts to build a cable. If it works, I'll consider making the cables for anybody who needs one.
One of the many hats I wear is IT guy for a school district, and I'll have plenty of time on my hands at work between the random spurts of insane busyness (like testing season, etc). So I can make cables for anybody else who wants 'em, for a reasonable price.
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