#avr Logs

Aug 16 2022

11:38 AM specing_ is now known as specing
02:16 PM kodcode: Hi everyone. A beginner here. I bought an USBASP and measuring VCC from the USBASP shows ~7V but it should be 5V. Why is that? Room to concern? Thanks in advance.
02:25 PM LeoNerd: That sounds wrong.. what is your USB port putting out?
02:27 PM kodcode: LeoNerd: Sorry, but not aware how to measure or where to look this up. I set the jumper to 3.3 and now I am measuring ~4.5V
02:29 PM kodcode: At first attempt when it was ~7V, the USBASP was already connected to my MCU on my breadbord and after connecting the USBASP the LED on the USBASP went on for a second and then off.. did I just burn my MCU 2 minutes after buying it?! :/
02:29 PM qu1j0t3: where are you seeing that measurement
02:30 PM qu1j0t3: avrdude?
02:30 PM kodcode: qu1j0t3: I measured with a multimeter
02:30 PM qu1j0t3: welll.... you had the leads backwards for one thing
02:31 PM qu1j0t3: and what LeoNerd said, you shouldn't see anything north of about 5v on usb power
02:32 PM kodcode: qu1j0t3: So my USB hub on my laptop is putting out too much?! Fixable?!
02:34 PM qu1j0t3: seems unlikely
02:34 PM qu1j0t3: but if so, you can measure again and verify
02:34 PM LeoNerd: Find something else to check your measurement with. Maybe the meter is mis-reading
02:34 PM qu1j0t3: it's very hard to think of a scenario where a laptop that is still alive would be doing that
02:34 PM qu1j0t3: what LeoNerd said. sounds like a measurement issue
02:37 PM kodcode: So how does this explain that if I have the jumper on 5V the LED on the USBasp goes off after a ms, but if I switch the jumper to 3.3V the LED stays on? (nothing else changed)
02:39 PM qu1j0t3: i'd be consulting the usbasp manual
02:39 PM qu1j0t3: i use an avrisp2 and avrdude gives a voltage reading from its ADC
05:29 PM kodcode: qu1j0t3: Thanks. So I switched to a different GND pin on the USBasp and it works. Looks like I got some cheap quality stuff...
05:30 PM qu1j0t3: doesn't really explain it, there shouldn't be 7v betwen any 2 points on it :-)
05:33 PM LeoNerd: Suggestion: Try putting a 10k to 100k resistor across the voltmeter terminals, and measure again. It's possible the really high impedence of a DMM might be getting confused by some spikey noise
11:39 PM specing_ is now known as specing