AC1082 mp3 playing chip, which pins have the alt functions for I2C to an EEPROM?

[Infraviolet]

I'm trying to modify an existing mp3 playing board, based around the Jieli AC1082 so it can save its current playing track to EEPROM. This capability notionally exists in the chip, I found the datasheet (in Chineses), put it through google translate and found this:

"Support external 24C02 as breakpoint memory."

Also

"A note about memory
(1) If the chip is equipped with an external 24C02 chip, all memory information will be stored in 24C02, which can realize breakpoint memory, volume, track, etc.
(2) If the chip does not have an external 24C02, all memories are stored in the TF card to achieve volume and track memory.
(3) If the user needs an external FM chip, 24C02 must be added to save the radio station information."

I've also found general pinouts for the 16 pin SOIC chip, and checked them against what is on the pre-made board (where pins are outputs from the chips or voltage/gnd pins I've been able to verify the right voltage or sort of signal is present).

The pinout is (going anticlockwise):
1. SD card data pin (SPI)
2. SD card command pin (SPI like)
3. SD card clock pin (SPI)
4. GPIO to connect by an array of buttons and resistors to ground thereby allowing the chip to read in button press combinations
5. USB D-
6. USB D+
7. grounded via a capacitor, goes to nothing else
8. Gnd

9. left audio out
10. right audio out
11. 3V3 output of on-chip regulator
12. V+ in, can take 3V3 to 5V in, to regulate down to 3V3 for internal use
13. Gnd
14. GPIO of some sort
15. output signal for status LED
16. supposedly an input to take NEC format infrared signals (after demodulation)

I am certain the chip in the board I am working on is indeed an AC1082 (also described as a KT2083, KT3083 or KT4083 depending on the revision of inbuilt software, the datasheet says all revisions support EEPROM saving of which track is playing so as to preserve this across being power cycled).

I understand that the chip has alternate functions on many of its pins, which will automatically work in alternate fashions depending on what is connected to them. The use of an I2C EEPROM such as the mentioned 24C02, which means any other I2C EEPROM with the same commands for various functionality should work too, will involve some pins being able to serve as I2C master pins when in an alternate mode.

Has anyone any knowledge of this part? It is a chinese one, so lacks the level of documenation you get for normal parts, but it is commonly used in a lot of module style boards for use in DIY projects, and quite common in mass produced consumer devices too (there was something a while back where loads of people online got interested in reverse engineering some sort of talking buddha statue ornament, after a bigclive video about it, and found a version of this chip in it, their discussions are one of the main results when searching about the chip).

However all I can find about it in regards to its use with an EEPROM are pieces of info on some forums in Russian and some forums in Chinese, both of which upon google translating just turned out to be someone recommending the chip to someone else for a project and including parts of the datasheet as they'd translated it. Still no clear note as to which pins perform double-function as I2C masters for use with an EEPROM.

Thanks

[MarkS]

Can you post a link to the datasheet? You posted more information Than I could find via Google. If the information is so limited, I'd recommend finding another chip.

[amyk]

Are you sure it's an AC1082? The markings these have are not all that obvious: https://raw.githubusercontent.com/kagaimiq/jielie/main/chips/chip-marks.md

Datasheet: http://www.yunthinker.com/FileUpLoad/DownLoadInfosFile/638064675478061915.pdf

Russian discussions including SDK and miscellaneous info: https://cxemi.ru/forum/11-14227-1

This feature may depend on whether it's been enabled in the firmware.

[Infraviolet]

Enabled in firmware looks to be the issue indeed. I found some hints that pin 1 (SD card data) can become I2C SDA and pin 3 (SD card clk) can be I2C CLK, yet when I fitted an EEPROM here with 10K pullups to the 3v3 rail nothing happened. Also I found pin 16 can supposedly accept NEC coded IR data packets, so I generated some such packets on a wire (with some low pass filtering to ensure the chip only received the signal it would after a TSOP38238 style receiver had demodulated an actual 38KHz NEC IR command) and fed them in there, chip did not respond. Looks like the manufacturer of the little mp3 playing module I was trying to improve had indeed not "enabled these features" despite the datasheet's claim that I2C EEPROMs are supported by all revisions of the chip.