Re: BlueSaab Amp pcb!

Posted by sbt on Dec 14, 2016; 2:03pm
URL: http://bluesaab-forum.90.s1.nabble.com/BlueSaab-Amp-pcb-tp737p864.html

Seth wrote

Here's the link to v1.2 of the Amp pcb

Thanks for the upload. Have now built v1.1 as boards just arrived from OSH Park. I used the recommended 2kΩ resistors to set the gain, which seems to work OK; I still need phone volume set to the maximum, but at least radio volume is close and telephone call volume also tolerable.

I do have an issue where the BT module isn't started properly on power-up with the amp fitted (symptoms are that neither BT led flashes or lights, and the module is not discoverable/connectable). I've built two amp shields and they both exhibit this behaviour, so I'm not sure it's the (new) hardware. It's pretty consistently a problem with the amp fitted, and never a problem without. I've tried loading the BT configure software to the module, but this works fine everytime the module is powered up; the issue only affects the SAAB-CDC software.

Fortunately I can reproduce it on the bench with USB connection to UPLOAD, so I'm working on adding some more logging around the initialisation of the BT module. Hardware version detection is working correctly and v5.0 is reported from RN52impl::initialize(), so my suspicion that the additional drain of the amp at power up was taking the analogue sense voltage out of range and skipping the correct RN52 power up sequence was incorrect.

Suggestions for further debugging welcome.