Application: Microphone (line-in from MIC-pre-amp) CODEC.
Using SPI interface.
The code was developed on both a –K and –U EVB. Both are USB-I2C (and the –K has a switch for SPI.) We have successfully run a 500 Hz tone generator (testing) and our more complex app.
We have accomplished the following:
1. Now on our target board which goes to production next month.
2. Have proven our power-supplies (not using internal LDO): 3.3 and 1.8V.
3. SPI: Chip-select, clock, data. (We do not have read-back capability on this board, although we did successful read-bask on the K-EVM). SPI clock is 250 kHz (below the 400 limit)
4. MCLK: Input clock is 3.3V CMOS-19.200 MHz. (Not used on eval boards).
5. Since we have ‘accidently’ (see below) have gotten that CODEC running on two different processors (Silicon Labs, and our board processor is a PIC24), we are confident the SPI integrity and our registers addressing is being done correctly.
The simple 500 Hz tone generator is loaded. Nothing happened. I probed pin 1 (MCLK) and accidently bumped to pin2-BCLK. It began to run. I was able to repeat that several times. However, if pin-1&2 were connected at power-up, nothing.
Schematics and Code being furnished by Phil Meyer
I suspect it has something to do with using the internal PLL, since the -U and –K eval boards used a 4 MHz clk from the TI USB-IC.
