Verification of Digital Input Circuit

AllyCat

Senior Member
Hi,

You have used the 8-pin "footprint" of an EEPROM for 6-pin optocouplers ? :confused:

There is no decoupling capacitor (e.g. 1ouF) shown across the supply rails (Leg 1 to Leg 8). Also, of course, the "components side" view is shown, not the copper-side track layout.

We always recommend including the PICaxe download/programming connections/socket on ALL prototype boards. Several of the resistors shown (i.e. R2 - R5) are not strictly necessary (there are "Weak Pullups" available on the chip) and moving the LED to Leg 3 would permit a normal programming/debugging interface to be included (on Legs 2, 7 and 8).

Cheers, Alan.
 

Bozambo

Member
Hi,

You have used the 8 pin "footprint" of an EEPROM for 6-pin optocouplers ? :confused:

There is no decoupling capacitor (e.g. 1ouF) shown across the supply rails (Leg 1 to Leg 8). Also, of course, the "components side" view is shown, not the copper-side track layout.

We always recommend including the PICaxe download/programming connections/socket on ALL prototype boards. Several of the resistors shown (i.e. R2 - R5) are not strictly necessary (there are "Weak Pullups" available on the chip) and moving the LED to Leg 3 would permit a normal programming/debugging interface to be included (on Legs 2, 7 and 8).

Cheers, Alan.

Hi Ally

DO appreciate your comments first of all the 8 pin "footprint"was used because a 6 pin footprint was difficult to locate.
Using micro controllers is new to me all that I have done is what I have read about IN THE MANUALS. SOMEWHERE I read again that those pulldown resistors are used to prevent eratic behaviour of the IC. With regard to the decoupling capicator is its use similar to that when it is used in a voltage regulator circuit? If the answer is yes I will do exactly that. Un fortunately I dont know much about debugging.what it seems to be suggesting is using some procedure to correct, or to find an error somewhere. The manual has a different explanatiion.
In the light of the above could you direct me to a schematic that would have all the features you have made mention of. I have searched the archives and could not find one. None of the manuals contain the features you are talking about.
thanks again.
Bo
 

AllyCat

Senior Member
Hi Bo,

The download circuit is shown in many places, particularly Manual 1, for example pages 27 and 44. Unfortunately, a supply decoupling capacitor is not shown, although one is included on all the project boards. For a simple circuit, the value is not too critical (10uF and/or 100nF are typical), connected across, and close to, the supply/ground pins, Legs 1 (+ve) and 8 (-ve). It's mentioned many times on the forum!

Typical input switch circuits are shown in Manual 3, particularly around Page 26. For unused inputs it is recommended to pull the pins low OR high (it doesn't matter which). The internal "Weak Pullup" resistors (about 35 kohms) are quite a new feature so are not well documented in the manuals, but explained in the PULLUP command in Manual 2 (~page 159).

Sorry, I don't think there is any single overall circuit diagram shown in the manuals, because there are just too many different possibilities. But there are often examples on the forum.

Cheers, Alan.
 
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