Using the Sony Spresense with amplifier circuit and external power

[kriover]

Hi,

I want to use acoustic microphones with a amplification circuit and have designed the circuit to match the bias input of the spresense, 0-1.8V. I tested with a power supply and that worked, but when I connected a 5V battery the audio input the audio pins do not work. I suspect this might have to do with the current supplied by the battery. Is there any specification of the input current on the board?

I use an inverting opamp with a capacitor and then an voltage divider to set the input voltage at ~0.8V. Can this be a problem? I might place a capacitor at the exit to better match the output of the circuit to the input of the board.

Any help is appreciated!

[CamilaSouza]

Hello, @kriover

Our FAQ have a note about batteries:
https://developer.sony.com/develop/spresense/docs/faq_en.html#_about_the_battery
https://developer.sony.com/develop/spresense/docs/faq_en.html#_about_spresense_main_board (The "What's the power consumption of the main board" might also help)

A few resources that might be able to help you:
https://www.hackster.io/karl-sony/spresense-audio-scope-e0c3d3 (This one talks about how to provide the bias voltage)
https://developer.sony.com/develop/spresense/tutorials-sample-projects/spresense-tutorials/using-multiple-microphone-inputs-with-spresense (Example connecting microphones to spresense)
https://developer.sony.com/develop/spresense/docs/hw_docs_en.html#_how_to_connect_analog_microphones (hardware guide to connect analog microphones)

I hope this links can help you with your project! Let me know if they were useful.