Teardown: Amazon Echo Dot 2 - Page 1
Forum section: electronics / general

author: NiHaoMike
author_rank: Super Contributor
timestamp: October 22, 2016, 07:15:17 am
content: Shortly after Amazon announced the Echo Dot 2, I wondered if it could be hacked to add S/PDIF output so I ordered one. I received it yesterday and started reverse engineering it.There's certainly more to it than I expected. Just the mechanical design appears very sophisticated, including a cast aluminum CPU heatsink and a rubber seal to prevent feedback.The motherboard has been completely redesigned since the first generation, replacing the TI CPU with a Mediatek MT8163V, specs similar to the Raspberry Pi 3. There's a chip marked KMFJ20005A that is obviously a memory chip, but even the capacity seems to be elusive to online searching. The RF transceiver is a MT6625L. What's odd is that based on the datasheet I could find, it seems to have a shared IF path for the Bluetooth and 5GHz Wifi. Maybe there are more shared blocks in the chip than what the block diagram would imply? There's a MT6323 mixed signal chip that handles the power and speaker output, and most crucial to the feasibility of adding S/PDIF, a TLV320DAC3203 I2S DAC.On the top board, there's the array of 7 microphones, 4 TLV320ADC3101 ADCs, and some mystery ASIC marked R3018. It's clearly handling the LEDs and maybe even interfacing the 4 ADCs?

author: Cyberdragon
author_rank: Super Contributor
timestamp: October 22, 2016, 04:07:18 pm
content: Yes, that chip is probably an IO interface for the ADCs too. I don't think they would use a custom chip just to control LEDs when an FPGA or even any old multi-channel PWM driver would work.

author: y999999
author_rank: Newbie
timestamp: November 08, 2016, 01:12:26 am
content: According tohttp://www.allaboutcircuits.com/news/teardown-tuesday-amazon-echo-dot-v2/R3018/R3019 is a MCU that controls the LED. I am not sure why they didn't implement the PWM inside an FPGA! The tear down also shows a UL1K

author: daqq
author_rank: Super Contributor
timestamp: November 09, 2016, 07:01:11 am
content: Thanks! That's a LOT of vias around the antennas. Strange that they would go for a such a cable, I would have guessed they would use a board to board connector.

author: actbluebe
author_rank: Newbie
timestamp: May 03, 2017, 09:57:45 am
content: Had anyone any success what an S/PDIF output?

author: NiHaoMike
author_rank: Super Contributor
timestamp: May 05, 2017, 05:46:25 am
content: I haven't had a chance to try adding the S/PDIF transmitter. I recall the logic is 1.8V which adds a little complication since the only S/PDIF transmitter chips I have on hand run on 3.3V.

author: actbluebe
author_rank: Newbie
timestamp: May 05, 2017, 08:52:41 am
content: Afaik I2S always uses 1.8V. I don't think an additional regulator would be a problem, but I am quite sure a 3.3V rail is somewhere in the device.

author: NiHaoMike
author_rank: Super Contributor
timestamp: May 06, 2017, 04:02:48 am
content: I2S usually runs at 3.3V, or at least that's what the DIT4192 I have on hand accepts. (It also accepts 5V logic levels, which is used in older equipment.)

author: actbluebe
author_rank: Newbie
timestamp: May 06, 2017, 06:48:56 am
content: Sorry, you are right! I think I am going to use a SN74AVC4T245 for the necessary level shift.