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PIcaxe 08M to 74141 problem
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"mimewar"
I had a working one tube counter, a simple 0-9. I was using the Basic Stamp board. I moved to a Picaxe 08M, and now, it won't count past 7. I goes 0,1,2,3,4,5,6,7, dark, dark, 0,1,2,3,4...
Anyone have any experience with the 74141 TTL chips and microcontrollers? Did I leave something tiny, but important out? I have the four output pins of the 08M, going directly to the 1,8,2,4 inputs of the 74141 ( and yes I made sure about 12 times that the outs and ins all correspond.. No caps, no resistors except on the HV input on the tube.. I looked at it enough so I know that 8, and 9 are the only two digits that involve pin 4 (binary input 8) going high. I have tested this on three different microcontrollers, and still nothing. Anyone have any TTL experience that may have a suggestion? Thanks Shane |
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Bill Esposito
[edited by A.J. - please trim quoted material]
On Sat, Aug 21, 2010 at 2:35 PM, mimewar <mimewar@...> wrote: I had a working one tube counter, a simple 0-9. I was using the Basic Stamp<snip> Have you manually checked (by tying the pins to VCC and GND) that your 74141 will actually produce 8 and 9? [Non-text portions of this message have been removed] |
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"mimewar"
I added a LED from pin 4 to ground to test the circuit. 8 and 9 now work, so i suspect the Picaxe I am using is supplying an overvoltage, about 2.3V too much. Anyone care to confirm?
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Shane --- In NEONIXIE-L@..., "mimewar" <mimewar@...> wrote:
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Adam Jacobs
Hi Shane,
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I think that your problem is most likely one of two things: 1) Something is wrong with your output routine for pin 4. Different microcontrollers will have different pin setups. Read through the manual very carefully on the new microcontroller on the subjects of setting up pins for output. Just because the same routine worked on pins 1-3 doesn't necessarily mean it will work on pin 4, all I/O pins on a microcontroller are not equal. 2) Possibly your 74141 has failed. They sometimes do that, although I don't know I've ever heard of one failing like that one. Still, if you have a spare to swap in, might be worth giving a try. -Adam On Sat, Aug 21, 2010 at 2:35 PM, mimewar <mimewar@...> wrote:
I had a working one tube counter, a simple 0-9. I was using the Basic Stamp |
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Bill Esposito
[edited by A.J. - please trim quoted material]
On Sun, Aug 22, 2010 at 9:47 AM, mimewar <mimewar@...> wrote: --- In NEONIXIE-L@..., "mimewar" <mimewar@...> wrote:<snip>I had a working one tube counter, a simple 0-9. I was using the Basic Ah-ha! That behavior smells exactly like the chip lacks a pull up on that pin. I looked it up and the PICAXE 08M is just a preprogrammed PIC12F683. Pulling up the datasheet for that chip ( ). Page 33 of that document tells me that, indeed, the chip lacks a pull up resistor when that pin (GP3 = physical pin 4) operating in IO mode. The datasheet specs that pin as only for input, so the easiest solution would be to use that pin as an input and pick some other pin to drive your high order bit. If you must use that pin, you can probably simply use a pull up resistor -- a resistor on the order of 10k tied from the pin to VCC (then connect to the pin normally -- make sort of a T). I've never heard of a diode being used as a pull up (push up?) like you did, but I'm pretty sure that's how it's working now. I actually got a hold of a picaxe for the first time ever this weekend, so I'm sure someone more experienced could chime in... |
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