Propeller Not recognized on Custom PCB design.

greybeard

Background:   Some time ago I build a simple prototype that contained a 3.3V regulator, an EPROM, a Propeller 40 pin DIP, and FT232RL with reset circuit.   With a lot of feed back from the community it finally worked well and continues to work.   With lessons learned, I integrated the Propeller  in the larger project PCB.   The first one worked without problems.   Revisions had to made to the  project PCB but still used the Propeller as used previously.  Basically had to move some components around.  
When I assembled the key components with the Propeller, 3.3V Regulator, EPROM, FT232RL and reset circuit on the new PCB but the Propeller is not found by the Propeller Tool.   I used a pre-programmed EPROM which the Propeller runs successfully on start up.  Just a simple program to set pins on and off at 1 second intervals.  
I used the MPROG3.5 from FTDI and USBVIEW from FTDI to inspect the FT232RL.  The FT232RL is not a counterfeit and is recognized.   In addition, the Device Manager (WIN8.1 PRO) installs a COM port.   The RX (pin 5) and TX (pin 1) lines from the FTDI to the pins 30 and 31 on the Propeller through a 150 ohm resistor. I did an ohm check from the respective pins on the FTDI chip and the Propeller and it measured 149 ohms on each.
I put a scope on both lines during the Propeller Tool hardware identification process.  I didn't seen any activity on either.   I do see activity on the DATA+ and DATA- input lines to the FTDI chip.   
At first blush it would appear that the FTDI chip is malfunctioning but I don't want to replace it until I have explored all possibilities.
Does anyone have recommendations.

Publison

As always, it's best to include the new schematic to see if you have overlooked anything. 
Recommendations can not go forward without it.

DigitalBob

 I like to build the FT232 like the prop plug. This way when you plug it in to the USB you can see the Led's blink and self test even with no propeller attached. Do you have the two 150R resistors in line from the usb to the FTDI chip.

jac_goudsmit

Did you check if you have the TX and RX lines switched? It's a common mistake.

===Jac

greybeard

Update. Pin1 of FT232 goes to Propeller  Pin 40 (P31) through 150 ohm resistor -- Verified pin to pin.  Pin5 of FT232 goes to Propeller Pin 39 (P30) through a 150 ohm resistor -- Verified pin to pin.

I did a loop back by connecting P31 to P30 on the Propeller Chip (not on the socket but directly on the pin of the chip).  The Propeller terminal echoes everything I type, even at max speed (3000000 baud).  No funny chars echoed.

So.....kind of rules out the FT232 as the source of the problem.   So...What am I missing.

Usually the most frustrating problem has the simplest solution!!!

Phil Pilgrim (PhiPi)

I suspect your problem lies in the reset circuit. Can you describe it, please? Or, better yet, post a schematic.
-Phil

greybeard

The Reset Circuit is a definite problem.  The DTR line from the FT232 goes low for about 30ms but the reset line on the propeller DOES NOT follows it. From what I read, lowering the Reset line on the propeller starts the recognition process from the Propeller Tool or loader.   Without the Reset, the process never starts.  Someone can correct me on that if they like. The Propeller will continue to run by loading the content of the EPROM.   The Propeller Tool simply reports that no Propeller was found. 
I have attached 4 Images.  The first is the Reset Circuit as drawn on the schematic.  A comparison with existing designs will show a striking similarity.  The Second image is the properties from Eagle of the 2n2222.  Notice it is a T018 case.   Image 3 is the pin configuration of the TO18 2N2222 transistor as cut from a datasheet.  and FINALLY THE CULPTRIT is the layout.  PIN 1 is tied to ground, Pin 2 is tied to the top of the resistor and to RT232 DTR through a capacitor and Pin3 is tied to the to the Propeller RESET and the pushbutton switch. Reference the schematic for the correct connections.
I don't know how this could happen!!!!! If the library is correct then I rotated, mirrored, swapped, or twisted the layout but I can't think of the combinations that would produce this.   I'll back-track through the libraries and see what I can find.
Once I correct install a part with the proper connections I will post an update.
Thanks for the support.

Hal Albach

I looked at five different 2N2222 datasheets, ON Semi, Philips, Central Semi, Multicomp, and Farnel, and they all show the T0-18 layout to be 1-Emitter, 2-Base, and 3-Collector with # 1 closest to the tab.  It looks like the one you showed is from ST.  It appears your layout is correct for 5 out of 6 datasheets.

jmg

Yup. convention is E-B-C starting from the tab, but the PCB looks to do that, so I'm not sure where the issue is.
The shown package has a rather strange pin-numbering scheme, but the pin-mapping is still the normal E-B-C

greybeard

Update Again:   I used the ST 2N2222 which as the Emitter and Collector reversed from those of the library 2N2222s.   As I said: The most frustrating problems have the simplest solutions.   
I basically forced the ST2N2222 into the board by putting a 'L' bend in the Base lead and rotating it 180 degrees.  Works fine.  Propeller Tool recognizes the Propeller and downloads code.  Runs Well.
PS:   The ST2N2222 wasn't used in my original Test Prototype. UGH!!!! 


Thanks for the  support.

Hal Albach

So much for convention!  I wonder why ST would make such a common device non-standard?

You might want to put some kind of note on that board re the unconventional ST 2N2222 or maybe just replace it with a plastic 2N3904.  After all, we're not using any special features known only to 2N2222.

Leon

The ST 2N2222 has the same connections as all the others:

http://www.st.com/st-web-ui/static/active/en/resource/technical/document/datasheet/CD00253894.pdf

DigitalBob

I looked at your schematic and I see your are using a 10k resistor. I always follow the build your own prop plug schematic. That one uses a 33k resistot at the base and I used a 2n3904 transistor . Mine all work perfect . So I can only suggest that you review the parallax prop plug drawing.

Phil Pilgrim (PhiPi)

Did you remember to connect nBOE to ground? If you did not, there's no internal pull-up on nRES.
-Phil

DigitalBob

I looked at your trace drawing and was wondering if you have the resistor and emitter to the ground plane.

Cluso99

I was caught by different pin outs between manufacturers of the plastic TO92 versions.

Plastic versions are often referred to as P2N2222

Any general purpose NPN transistor should work.

The transistor circuit causes a short pulse to ground on the reset line when DTR goes active (which is 0V on the ttl side is the Ftdi232 output)

Toby Seckshund

only a guess ---

The internal pull - up resistor in the Prop is only enabled if the BOE pin is in the right state (grounded I think, from work)

Tymkrs

greybeard wrote: »

Update Again:   I used the ST 2N2222 which as the Emitter and Collector reversed from those of the library 2N2222s.   As I said: The most frustrating problems have the simplest solutions.   
I basically forced the ST2N2222 into the board by putting a 'L' bend in the Base lead and rotating it 180 degrees.  Works fine.  Propeller Tool recognizes the Propeller and downloads code.  Runs Well.
PS:   The ST2N2222 wasn't used in my original Test Prototype. UGH!!!! 


Thanks for the  support.

I've gotten caught by this one before and now just make sure to check any 3-lead component. Glad you were able to find out what was going on and that it worked!