Connecting the codec to BeagleBone

Post date: Apr 17, 2016 1:29:52 PM

The maxim codec can be used from windows for testing purposes and it gives you a graphical screen to manipulate the codec while you put music to it.   But we are not concerned with that of course and we are giving you instructions on using the codec with our software on the beagle bone that has been customized to use it.

We use I2S lines from the beaglebone and the built in 24.576 mhz clock also from the beagle.  Our code when you fire up the beagle will disable HDMI so expect to have to use SSH to log into linux on the beagle. 

The beagle will still need a usb cable to the codec,  this is for Control and status return information.  We use a built in driver for the Beagle called FTDI which is basically UART over USB and we provide a standalone FTDI linux routine that allows you to send single commands to the codec for testing.  I2C would also work but that requires more wires and configuration changes on the beagle and codec. For us FTDI is fast enough and is reliable.  

Unlike usb audio, I2S works very well as in no over-runs or under-runs at least we have never seen any except under highly stressful conditions that should never occur.  

Here is a datasheet on the eval board from digikey.

http://datasheets.maximintegrated.com/en/ds/MAX98089EVKIT_WLP.pdf

Your going to need to do a little soldering on the maxim.  Or if you have the little clip on test connectors they may work. Just make sure you have a good connection.

Click above image for large version. 

For starters we will do beagle to maxim plug in pins.

On the maxim you have JU19 which is where a lot of connections are used.  This is for I2S.   Pay attention to bank on The maxim.   Most connections (except ground which is on bank1) go to bank2

Remove existing jumpers on JU19.  Now wire it this way. 

Maxim                                    Beagle     Type

JU19                                      P9

Bank 1 LRCLK2 <----------------> Pin 2      Ground

Bank 2 DAC2    <----------------> Pin 28     Digital to Analog Convertor

Bank 2 ADC2    <----------------> Pin 27     Analog to Digital Convertor

Bank 2 LRCLK2 <---------------> Pin 29     Left / Right timing

Bank 2 BLCK2   <---------------> Pin 31     BLCK timing. 

Remove existing jumpers on JU12

Maxim                                   Beagle

JU12                                     P9

Middle Pin         <----------------> Pin 25   MCLOCK 24.576 mhz.

See below pin layout for better idea, 

x

Ox

x

The Maxim is a power hungry device, as it has the ability to drive speakers up to 2 watts a channel. It requires 3.3 volts from the beagle in addition to the 5 volts it gets from usb.,  and these connections either need soldered or test jumpers.

                                             P9

SPKVDD    <--------------------->  Pin 4    3.3 Volt

GND          <--------------------->  Pin 1     Ground

Maxim inconveniently did not provide RCA connectors for line out.   So you must hook up your own, if you dont want to use them just use the headphone output.  With the proper adapter you can still use self powered speakers. 

Line outs. 

RXN Left output to rca connector

RXP Right output to rca connector.

Use a nearby ground for rca center tap on both connectors. 

Now hook up provided usb cord from beagle / usb hub to the USB connector on the maxim labeled Control.

Your now ready to fire things up,  make sure you have at least 2 amp 5 volt usb or direct supply to the beagle.