BB AI Voltages.

[andrew...@iosaudio.co.uk]

Hi Guys,

I am having some strange things going on with voltage levels and voltage drop.

First I noticed issues when powered from my MacPro, If I loaded the cpu then the board could reboot, it could also get in a state where it needed multiple reboots to get started.

So I connected up to a 2.5A USB supply and this issue goes away.

Another issue I am seeing though is I am only getting 4.6V on SYS_5V. I have connected a BBB to the same supply and see 5V on SYS_5V.

Also under cpu load SYS_5V drops to 4.3V.

When powered from the MacPro SYS_5V is 4.3V and drops to 4V under load and reboots. I tested a BBB connected to the MacPro and only get 4.7V on SYS_5V.

Also when connected to the power supply VDD_5V is only 2.16V.

Has anyone got any idea what might be going on here?

Many thanks

Andy

[Jason Kridner]

On Thursday, September 26, 2019 at 5:09:06 PM UTC-4, andrew...@iosaudio.co.uk wrote:

Hi Guys,

I am having some strange things going on with voltage levels and voltage drop.

First I noticed issues when powered from my MacPro, If I loaded the cpu then the board could reboot, it could also get in a state where it needed multiple reboots to get started.

So I connected up to a 2.5A USB supply and this issue goes away.

Another issue I am seeing though is I am only getting 4.6V on SYS_5V. I have connected a BBB to the same supply and see 5V on SYS_5V.

Also under cpu load SYS_5V drops to 4.3V.

When powered from the MacPro SYS_5V is 4.3V and drops to 4V under load and reboots. I tested a BBB connected to the MacPro and only get 4.7V on SYS_5V.

This much drop on SYS_5V is certainly unexpected. Do you have some kind of load on it or just the probe?

BeagleBone AI should peak out about 1.8A (9W) under full processor/memory/flash load (including DSPs/EVEs/etc.). I don't know what your MacPro is outputing. 5W (1A) is much more typical.

I find something like https://www.amazon.com/Satechi-USB-C-Power-Tester-Multimeter/dp/B01MT8MC3N/ to be really useful for monitoring the current consumption and voltage.

Which port of your MacPro are you using and is it actively connected to a power source (not just battery)?

 

Also when connected to the power supply VDD_5V is only 2.16V.

On BeagleBone AI, VDD_5V is input-to-BeagleBone-only, so the voltage really isn't of interest.