Saturday, June 28, 2014

An Internet music player pt3

The three subprojects mentioned in previous posting can in fact be regarded as one project, viz., connect the Wiz550io to the GA144 and output the stream of PCM codes as a webserver response. Conversion to streamed MP3 is icing on the cake. Booting from Flash is additional icing. Designing and building a PCB to hold the circuit will be the icing, cream and two cherries on top.

I've added two headers to the EVB001 prototyping area and wired them to the SPI connections of node 705. Thankfully realised that Wiz550io uses 3.3v levels but node 705 pins are at 1.8v levels. So I wired one of the spare level converters into the path.

Running Wiz550io from 3.3v required me to add a 3.3v source. Using my Dangerous Prototypes ATX Breakout Board to supply the 3.3v, I also realised I could add a jumper to the 5v supply connection and remove the 5v wall wart I had been using.

So now, using the examples in Ch 9 of ArrayForth Users' Guide, I can switch on the SPI pins DO, CLK and CS and see 3.3v levels on the corresponding pins of the socket for the Wiz (MOSI, SCLK and SCSn). On the EVB001 these pins are hidden behind some selection logic but there are some test points on the board to verify the correct responses.

Next step is to write some code to run the Wiz550io from node 705. Need word to get an IP address from DHCP server on network (overriding default IP). Need word to echo text back to client.

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