Content originally posted in LPCWare by tanabe on Sun Oct 18 22:15:34 MST 2015 Hi,
I'm using LPC4357 chip, I want to play audio at GPIO interrupt, so setting DMA transfer from memory to I2S peripheral in GPIO interrupt function. then L/R channel output is inverted occasionally. My procedure is: 1. Setting I2S output format (32bit Stereo) 2. Turn I2S_DAO RESET bit to 0 (STOP bit is 1)
In GPIO interrupt, 1. Set DMA, and start transfer. 2. Wait TX_LEVEL is to higher than TX_DEPTH_DMA1 3. Turn I2S_DAO STOP to 0.
In this procedure, it will occur once per 1000 times that L/R channel inverting in output. Inverting occurs only at beginning of transfer.
Why occurs Inverting?
And, I found work-around for this problem with substitute procedure in GPIO interrupt. New procedure in GPIO interrupt is: 1. Write 0 to I2S_TX_FIFO. 2. Turn I2S_DAO STOP to 0. 3. Wait TX_LEVEL is 0. 4. Set DMA, and start transfer.
Then, L/R inverting never occur. But, I don't understand why the procedure can avoid the problem. Does the work-around do well?
