novel prawn
I'm going to post this schematic; forewarning—it is most likely almost entirely incorrect. Don't feel obligated to help. The USB wiring is my main concern, any suggestions/corrections would be highly appreciated. The circuit I made is a copy of another one I found online for audio boosting, which I cautiously believe is mostly correct. Feel free to share any improvements, corrections or alterations of that matter!
prime abyss
without looking at the function of the circuit, yes the usb wiring is not correct, first off you should connect gnd and shield, you also need 5.1k resistors from CC and Vconn to gnd, at the same time I would recommend using a connector with fewer pins if you just need power
also I assume your opamp supply is wired the wrong way around
why are D+ and D- connected to gnd and the opamp output?
novel prawn
without looking at the function of the circuit, yes the usb wiring is not correc...
ill switch it to one with fewer pins, but the honest reason I put the Ds to gnd and opamp is that I saw a dude do it with a mouse and had absolutely 0 idea where they were supposed go so connected them somewhere.
rugged basin
without looking at the function of the circuit, yes the usb wiring is not correc...
regarding connecting shield to gnd, if this is a device (not host), I've seen some arguing it should be connected and others not connected. I don't think there's a conclusive way it should be connected.
prime abyss
regarding connecting shield to gnd, if this is a device (not host), I've seen so...
it used to be a discussion but at this point it's irrelevant, the usb c spec mandates a direct connection in the plug so no matter if you place a capacitor or a bead or anything, it's shorted in the cable
rugged basin
while technically you can connect anything to any of the USB cable if you control both ends, I wouldn't use it as a convenient connector and rather follow the usb spec, which definitely doesn't allow analog audio through the data lines (I've seen usb and hdmi connectors used for stuff...other than usb and hdmi, but only internal to a device)
rugged basin
it used to be a discussion but at this point it's irrelevant, the usb c spec man...
I knew of that on the host side, but on the device side as well? that's news to me. I gotta re-read the usb spec sometime Found it, to those who are curious it's in section 3.4, as note 6 below any table
novel prawn
which lines should the output be connected through? I thought D+ & D- were data?
rugged basin
which lines should the output be connected through? I thought D+ & D- were data?
they are data, but there's a whole protocol behind that. you would need some kind of audio-to-usb interface, whether that is DIYed or an off-the-shelf chip (which there's probably a ton out there)
novel prawn
I guess ill look for a chip that this connects to instead
theres the pcm2902 which I looked at before this, but it is intimidating
prime abyss
there used to be an alternate mode for analog audio but it got deprecated so if you only wanna use 1 usb cable there isnt really a good way, you could use differential signaling and ac couple both signals and use the sbu pins in alternate mode but yeah.. it obviously wont work with any normal device to get audio like in your original schematic
novel prawn
there used to be an alternate mode for analog audio but it got deprecated so if ...
ill probably end up using one of the chips like the pcm and figure it out as I go
anyway, im going to bed for now, sorry if I infuriated you by just not knowing obvious things. Have a nice night
prime abyss
lol youre good no worries
rugged basin
it's all part of the learning experience
random ether
theres the pcm2902 which I looked at before this, but it is intimidating
This chip is nrnd. I'd just use a microcontroller.
There are also codecs like PCM2912A that have an integrated microphone amplifier, they're cheaper too.
novel prawn
There are also codecs like PCM2912A that have an integrated microphone amplifier...
Should I use something like an atmega 32u4? Or some other microcontroller
random ether
Should I use something like an atmega 32u4? Or some other microcontroller
You'd want something with a decent ADC, I think there's a newer version of that TI chip you listed though
Probably not very friendly for soldering if you're not experienced though
novel prawn
I've soldered a bunch of SMD sod323 diodes which were pretty small, but I think soldering that chip would be a challenge
random ether
There's a newer version of the PCM2900 called the PCM2900C, it looks like it would fit the bill pretty well
novel prawn
Just took a look for that chip and found a 2900CDBR, will that work the same?
random ether
Yup. Just follow the reference design for the 2900C instead of the 2900, they aren't the same chip
novel prawn
alright
novel prawn
im not sure whether the output should be VINL or R, but is this correct so far?
