Noisy HC-05

Thread Starter

spinnaker

Joined Oct 29, 2009
7,835
Seeing this on the transmit out pin of an HC-05.

upload_2018-11-13_15-2-39.png

It seems to be enough to trigger the receive interrupt flag on my scope,

Far worse if I am sending data to the device. P,S, I have not changed the time base here.
upload_2018-11-13_15-11-16.png


Has anyone seen this anything I can do about it otther than replacing the HC-05?
 

dl324

Joined Mar 30, 2015
12,783
Do you have adequate power supply decoupling?

I was searching for a problem in an LED cube I'm prototyping. I thought it was timing or cross-talk pickup from long wires. After days of troubleshooting, I found out it was supply decoupling. I had stuck an electrolytic and a couple ceramic caps I had handy and that wasn't sufficient.

That was the first time I ever had a problem with power supply decoupling. But the cathode drivers can switch up to 300mA.
 

Thread Starter

spinnaker

Joined Oct 29, 2009
7,835
Do you have adequate power supply decoupling?

I was searching for a problem in an LED cube I'm prototyping. I thought it was timing or cross-talk pickup from long wires. After days of troubleshooting, I found out it was supply decoupling. I had stuck an electrolytic and a couple ceramic caps I had handy and that wasn't sufficient.

That was the first time I ever had a problem with power supply decoupling. But the cathode drivers can switch up to 300mA.
I would hope it would have its own on board circuitry. But you might be on to something. I I raise the supply voltage the noise ratio becomes less and less.

What would you recommend for decoupling?

P.S. Power is currently being supplied by by bench supply.

I have never seen this issue before. Always worked out of the box.
 
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