DAC for use with nrf51822

[Alison Sinclair]

I am using the nrf51822 evaluation board and was planning to use it with sound. There is no DAC included in the board so can anyone suggest a good DAC to use with the board? Thanks

[Håkon Alseth]

Hi Alison,

The nRF51x22 is not aimed at sound and audio, as it does not have a I2S HW module, which is the preferred audio-bus of most DACs. What kind of audio output do you need?

Best regards Håkon

[Alison Sinclair]

I want to play a wav file through a small speaker, like one for a mobile phone.

[Håkon Alseth]

Hi Alison,

Unfortunately, it's not straight forward to do this, as we do not have a I2S interface. You can use the ADC (10 bit, 14 kHz max sampling at this resolution) and emulate PWM using a TIMER to output the audio on the receiving radio.

Best regards Håkon

[Philip Freidin]

There are many DACs that can be interfaced with either parallel, I2C, or SPI.

I did a quick search at DigiKey for DAC, 8 to 12 bits, SPI interface, 1 channel, SMT, settling time 1us to 5us, Tube or cut-tape. I got 24 hits. Lowest price is MCP4901-E/SN from Microchip. This would give probably quite acceptable voice playback, but music would not be very nice. Number of bits and sample rate are obvious parameters, but also the quality of your speaker will also limit what you can achieve. The SPI port is certainly fast enough to do higher quality sound, if the speaker can reproduce it.

Here is a pin compatible 12 bit DAC MCP4921T-E/MS for about twice the price of the 8 bit one.

[David Garnett]

You can also cobble together a DAC using the ADC, a GPIO pin and a PID algorithm. See:

www.edn.com/.../Create-a-DAC-from-a-microcontroller-s-ADC