esp8266 newbie - where's the DMA precisely?

[espressif]

esp8266 newbie - where's the DMA precisely?

[papadeltasierra]

For anyone working on this, I discovered yesterday that if you use the I2S/SPI interface in a 'send limited memory block, interrupt on completion' mode, the function of the GPIO pin seems to be 'reset to default' when the interrupt trips. So when I wrote new data and triggered the send a second time, nothing seemed to happen but actually the DMA/I2S/SPI stuff was fine, but I needed to reprogram the GPIO pin again before starting.

[MswPaulDSmith]

Aha - seems all the magic is in mp3/driver/i2s_freertos.c. All rather 'black box' though - is there any documentation for these incantations and interesting register writes? For example, I think I might need to either use a different set of calls or a different (slower) timer if I want to (mis)use the I2S interface for my project.

[Spritetm]

Sorry, there's not really any other information on the i2s hardware at the moment.

[papadeltasierra]

Jeroen,

Thanks for the feedback. FYI the driver has a slight error – you can only divide the clock rate down by at most 63 x 63 not 127 x 127. I’ve managed to (mis)use the interface by sending 32-bits for every true data bit meaning I’m running the clock at 32-times the speed I really wanted. But it works a treat!

However next time I’ll probably use the HSPI interface instead as it looks like that can be done in a similar manner but with a lower clock speed.

Paul DS

P.S. I will release my code once I’ve had time to finish tidying it up. Teenage children and their exams are slowing me down .

From: Jeroen Domburg
Sent: Tuesday, May 24, 2016 7:33 AM
To: espressif/ESP8266_MP3_DECODER
Cc: papadeltasierra ; Author
Subject: Re: [espressif/ESP8266_MP3_DECODER] esp8266 newbie - where's the DMA precisely? (#17)

Sorry, there's not really any other information on the i2s hardware at the moment.

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