Just like this is not very helpful. But I already know there are 3 devices on the bus. EEPROM, PLL and LCD driver. By little bit of playing around I h

Reprogramming "old" Sennheiser SKM 3072-U - Part 2 - I2C

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2021-06-11 09:00:06

Just like this is not very helpful. But I already know there are 3 devices on the bus. EEPROM, PLL and LCD driver. By little bit of playing around I have found out that 0x3E is display since it I can see it changing in the log as Im pushing the buttons. It even makes lot of sense since you can see quite huge portions of data sent to the adress the display has 6 times 8 segment for displaying numbers, 2 dots, 2 times bargraph for audio and RF 8 segments each, RF labels and BAT label. That means 6*8+2+2*8+2= 68 segments. So I would need around 9 bytes to encode it all, naively speaking. So it actually makes sense. And datasheet for it is nowhere to find and since I dont have to care anyway its enougth.

There is also misteryouse 0x7F which I suspected to be PLL. After looking at the manual I have found out that it need to set on of its inputs LOW in order to accept the data from I2C. So I added next channel to logic analyzer which was hooked to this pin. And started recording.

Then there is 0x50 and 0x51. This actually confused me a lot on the begining but after all it can be simply put into the phrase RTFM (Read The F* Manual) well, in this case EEPROM datasheet. It truly is EEPROM as suspected and its address is desrcibed in the DS. You can change the adress by setting high or low two of its inputs. So in theory you may creat array of 4 EEPROM using same chip. But in the mic both E1 and E2 are set low, so the adress should be 0x50. Then why 0x51? As clear from the table below, the memory is split into two blocks(halves) and by setting last bit of its address you can choose the block!