Two 16F84 pics using one piezo?

[Rubicon]

Thanks for all the reply posts.

Ingvar was right on the money with "Try making the pin INPUT right after each soundgenerating command."

I'd originally had TRISA = %11100, PORTA.1 an output but had changed it to an input before my original post. That had made the first startup beep go. Having read that due to DC bias the port should be an output and idled low I'd added a line after each SOUND command - PORTA.1 = 0 but that hadn't worked. Changing it to TRISA = %11110 made it work well enough. When the LEDs reach an end at a different time there's a regular beep. If the same time there's a slightly louder beep. If I make it beep twice or more per LED bank at either end and they reach it at a slightly different time then they fight it out with sometimes a squalk or two.

I have a question also. In the manual it stated that the SOUND command automatically makes a pin an output. I wasn't sure if it makes it a pin set as input an output for the duration of the sound then returns the pin to an input or not. From the look of it it doesn't. Does this apply to all the other commands that automatically change a pins state or are there exceptions?

I haven't tried the PortA.1-capacitor-piezo-PortA.1(on other pic) setup yet and sougata has put me off a little. If it's safe for the PICs I'll give it a go.

Many thanks,

Rubicon.

[mister_e]

i can't comment on the SOUND command but if it's like PWM, sometimes the pin return to Input, sometimes to Output state so...

As producing sound is not a big job, i suggest you to build a few line routine for that. That way, you'll be able to reach the exact resonnance frequency and get the maximum SPL of your piezo.

Don't worry, the suggested method is safe.

[sougata]

Hi,
Use a series limiting resistor and give the port to port via capacitor scheme a try. You bet you can produce interesting effecting where one PIC generates the sound and the other modulates it.

A recommendation would be to use a non-polar cap. Or two electrolytes back to back.

BTW in this scheme both has to be an output.

Regards

Sougata

[Rubicon]

O.K then I'll give it a go and report back.

I suppose if I really didn't want any beeping conflicts I could make the program check the pin for an input voltage before a SOUND command and if there is a voltage present then use another routine.

Rubicon.

[Rubicon]

With both PICs PORTA.1 pins set as outputs and making them again outputs after each SOUND command just to be sure I tried the PortA.1-1uF ceramic capacitor-piezo-PortA.1 and PortA.1-10uF electrolytic capacitor-piezo-capacitor PortA. schemes.

With both schemes I got the regular beep, a slightly louder regular beep and if both LED banks were completely in-sync the beeping sped up by a what sounded like a factor of four. That was it.

Many thanks again,

Rubicon.