BS2 "bare bones"
davejames
Posts: 4,045
in BASIC Stamp
Hi All,
I am embedding a BS2 SSOP into my current project. It will not have any need to communicate to the outside world.
It's pretty clear as to what needs to be done with the following pins:
- pins 1,2,14 (Vss)
- pins 3,4 (Vdd)
- pin 5,6 (SDA, SCL for EEPROM)
- pins 26, 27 (X0, X1 for resonator)
- pin 28 (RESET/)
Not clear is what's to be done with pins 7 and 8 (Rx, Tx) since there will be no outside communication with the BS2. Pull them high, pull them low? Put 'em in a paper bag and swing it around my head while clucking like a chicken?***
Can anyone clarify?
***obscure Dick Van Dyke Show reference.
I am embedding a BS2 SSOP into my current project. It will not have any need to communicate to the outside world.
It's pretty clear as to what needs to be done with the following pins:
- pins 1,2,14 (Vss)
- pins 3,4 (Vdd)
- pin 5,6 (SDA, SCL for EEPROM)
- pins 26, 27 (X0, X1 for resonator)
- pin 28 (RESET/)
Not clear is what's to be done with pins 7 and 8 (Rx, Tx) since there will be no outside communication with the BS2. Pull them high, pull them low? Put 'em in a paper bag and swing it around my head while clucking like a chicken?***
Can anyone clarify?
***obscure Dick Van Dyke Show reference.
Comments
How are you going to program it?
DB - I'm a "why guy". Can you elaborate on the why of pulling pin 7 high?
Dave
I agree. How are you going to program the critter?
Mascot away. No messages accepted.
***Obscure Return of the Jedi message.
Gen & Buck- the EEPROM will be pre-programmed with the desired code via a Stamp OEM board. That board has a DIP socket for the EEPROM. So after I download the code to the OEM board, the EEPROM is removed and installed into my project.
Dave
I would put 10K pull ups on both. Not absolutely necessary, but some bad experiences have convinced me that leaving I/O pins floating is not a good idea even if they are not used in the code.
***also the punch line of a popular phone prank way back in the stone age (before cell phones).
How are you testing your freshly soldered boards since there is no programming port?
Also, do you not want the programming port because of cost or because you don't deem it necessary?
And consider the possibility that you may have to reprogram those units in the future due to a problem or requests.
WBA - thanks much for the input. I forgot...duh!...about the pullups on SCL and SDA as per I2C requirements. I'll add them to my schematic.
Dave
kwinn - thanks for the input.
Dave
My old technical instructor heart jumped for joy when I read your questions. They were excellent! Great questions clearly stated, and full of insight. I would have physically jumped, but the uncontrolled oscillatory action of belly fat would have been not a sight to see.
So to the questions, but first a bit of back-story...
My project was conceived, then bread-boarded for functional proofing (aka debug). A BS2 module was used as the controller.
The schematics were cleaned up and sent to a PC board designer. After a bit of back-and-forth, layout drawings of the PC traces were given to me for "red-lining" where I prove every trace goes to were it should.
The OK to send the design files to the fabrication house was given after I approved the layout. At this point, confidence is high that things will work.
Once the boards arrived, one board was assembled with all the usual components and a BS2 module was put into its temporary place to prove functional operation of the board. (see attached image) Now the confidence level is quite high that the rest will work as designed after assembly.
The remaining boards will be assembled with the "bare-bones" BS2 circuit and checked for functionality. At this juncture, I don't need the programming port as the EEPROM has been pre-programmed with functional code via a Stamp OEM board. (see other attached image) If any particular board doesn't work, then debug will progress as usual in checking physical connections and electrical action.
That was all for your first question!
Second question: basically, don't need the port. And that means less parts/less cost. :thumb:
Third question: should future problems or updates occur, I'll send the customers a new EEPROM - or they can send their unit in if should they not feel up to swapping a socketed, 8-pin DIP device.
Regards,
Dave
----
Mascot away.
It was a small board that contained a BS2 interpreter IC (600mil DIP), EEPROM (8-pin DIP), and all the other standard size components needed for the serial interface. It came un-assembled for ~$35, which was quite a bit less than the BS2 module at ~$50. Great product it was. Bought a few. Used a few.
Plugged into it is the Parallax USB/Serial converter.
So what I've done is removed the OEM board's EEPROM, jammed in a ZIF that allows me to easily pop in/out EEPROMs after they've been programmed.
Dave
One pin failed to be soldered correctly, but I caught it during debug. The signal in question made it to the SSOP pad, but didn't show on the pin itself; had to use a jeweler's loop to see it. :nerd:
Once the pin was "touched" with an iron, the board came alive with complete functionality. Yay!
Thanks to all that offered some insight. :thumb: