Hey, apologies for the complete lack of updates, been a busy few months - I've put in an hour here and there working away on making USB etc work on the latest cAMP design and making DC/DC switching work without audible clicks... never really got anywhere with it due to the lack of time to work on it.
Decided to put the good one on hiatus, put out a simple design that'll satisfy most people, and bang out the cAMP Basic.
- LT3652HV solar charger
- 2 channel TPA3118D2 audio amplifier
- "ground loop breaker" differential audio input
- Fixed highpass audio filter, applicable to standard Boominator design.
- 5V output with 2.5A available current for charging things. Runs all the time unless the battery's dead.
- Separate 5V output that switches on/off the same time as the amp. Intended to be used with USB thumbdrive style bluetooth audio adapters, so you can bury one inside a Boominator and use a single switch to turn everything on.
- Automatic low-battery power off.
No DC/DC, DSP or no-audio shut down. That'll get done sometime in the future
Schematic's done, about to start working on the layout.
Decided to put the good one on hiatus, put out a simple design that'll satisfy most people, and bang out the cAMP Basic.
- LT3652HV solar charger
- 2 channel TPA3118D2 audio amplifier
- "ground loop breaker" differential audio input
- Fixed highpass audio filter, applicable to standard Boominator design.
- 5V output with 2.5A available current for charging things. Runs all the time unless the battery's dead.
- Separate 5V output that switches on/off the same time as the amp. Intended to be used with USB thumbdrive style bluetooth audio adapters, so you can bury one inside a Boominator and use a single switch to turn everything on.
- Automatic low-battery power off.
No DC/DC, DSP or no-audio shut down. That'll get done sometime in the future
Schematic's done, about to start working on the layout.
Gonna add a bit of "customer proofing" to the card to handle ESD and (minor) miswiring, and that should be it.
Rather than a switched +5V, I decided it'd be more useful to throw down a TPS2513 dedicated charging port controller. This chip controls the USB data lines so you'll be able to charge both Apple and Android stuff.
Once this card is designed, my next project might be a bluetooth receiver that works with this card. KC Wirefree makes a really good looking bluetooth audio module with very low standby current, shouldn't be much work to put it on a simple card that turns the Boominator on/off when you pair with it. If you use a NFC sticker for paring, concievably you could build a Boominator without any buttons/stickers/etc on the outside.
Ok, pulled back the order and submitted another one. After skimming the TPA3116 thread and realizing people think it's a pretty good sounding amp, I decided to put in a bunch of changes to make it sound a little better. Probably adding $5-6 to the cost of the thing, I apologize
- Output filter caps changed to film caps (previously big X7R's)
- Output inductors changed from DR127 to Coilcraft JA4575
- 2 layers of decoupling on the TPA power supply
- AM0/1 and MODE pins brought from the TPA to the AVR, allowing switching frequency and operating mode to be adjusted to trade off SQ for idle power consumption. I'll probably provide DIP switches or jumpers in the future for configuring this, it'll be set on the prototype by strapping pins on the ISP header.
- Every signal cap in the audio chain is now film or NPO ceramic.
Idle loss is made no worse by these changes.
There's some other things people are doing in the TPA thread (bootstrap snubbers, etc) but if people want to go that far, by all means go ahead (but if you blow the TPA, no I won't fix it for free )
- Output filter caps changed to film caps (previously big X7R's)
- Output inductors changed from DR127 to Coilcraft JA4575
- 2 layers of decoupling on the TPA power supply
- AM0/1 and MODE pins brought from the TPA to the AVR, allowing switching frequency and operating mode to be adjusted to trade off SQ for idle power consumption. I'll probably provide DIP switches or jumpers in the future for configuring this, it'll be set on the prototype by strapping pins on the ISP header.
- Every signal cap in the audio chain is now film or NPO ceramic.
Idle loss is made no worse by these changes.
There's some other things people are doing in the TPA thread (bootstrap snubbers, etc) but if people want to go that far, by all means go ahead (but if you blow the TPA, no I won't fix it for free
)
Final card layout, pulled it back again and made room for DIP switches. Two select amp frequency (400K-1000K), one selects BD/1SPW amp mode, and one selects lead acid or LiFePO4 battery chemistry.
The 12V->5V regulator on the PCB is synchronized to the amp to prevent frequency beating between the two. Crossing my fingers that compensation is fine over the 400KHz-1000KHz frequency range of the amp.
Now to start banging out the AVR software..
The 12V->5V regulator on the PCB is synchronized to the amp to prevent frequency beating between the two. Crossing my fingers that compensation is fine over the 400KHz-1000KHz frequency range of the amp.
Now to start banging out the AVR software..
Just threw together a Bluetooth experimentation card. Using a Roving Networks RN52 instead of the KC Wirefree module.
J1 upper left: USB for updating RN52 firmware (won't be in final design) also can supply power.
J2 lower left: +5V input, cAMP enable, ground
J3 upper right: analog audio output
J4 lower right: bluetooth pushbutton input, bluetooth LED output.
U5 on the right: optical SPDIF output. Won't be in final design, but I'm integrating one of these cards into my home stereo so visitors can play music from their phones.
How this will work:
- Normally the card is in sleep mode, consuming uA of current (everything's off)
- To connect, push the bluetooth button. The card will wake up and wait for a connection, if there's no connection within 30 seconds or so it'll go back to sleep.
- To pair a new device, push/hold the bluetooth button. The card will make itself discoverable so you can pair with it.
- Once a device connects, it'll turn the cAMP on. If no audio plays for ~30 seconds it'll turn the cAMP off to save power, turning it on right away if audio starts playing again.
The RN52 supports SPP so the card should be configurable over bluetooth using a text menu, this will let you set PIN codes, device name, change timeouts, etc.
The RN52 normally ships with SBC codec support only, but is available with firmware that'll do AptX and AAC codecs if you pay a license fee. Gonna be looking into that.
J1 upper left: USB for updating RN52 firmware (won't be in final design) also can supply power.
J2 lower left: +5V input, cAMP enable, ground
J3 upper right: analog audio output
J4 lower right: bluetooth pushbutton input, bluetooth LED output.
U5 on the right: optical SPDIF output. Won't be in final design, but I'm integrating one of these cards into my home stereo so visitors can play music from their phones.
How this will work:
- Normally the card is in sleep mode, consuming uA of current (everything's off)
- To connect, push the bluetooth button. The card will wake up and wait for a connection, if there's no connection within 30 seconds or so it'll go back to sleep.
- To pair a new device, push/hold the bluetooth button. The card will make itself discoverable so you can pair with it.
- Once a device connects, it'll turn the cAMP on. If no audio plays for ~30 seconds it'll turn the cAMP off to save power, turning it on right away if audio starts playing again.
The RN52 supports SPP so the card should be configurable over bluetooth using a text menu, this will let you set PIN codes, device name, change timeouts, etc.
The RN52 normally ships with SBC codec support only, but is available with firmware that'll do AptX and AAC codecs if you pay a license fee. Gonna be looking into that.
Wouldn't call it dedication, this has been a spare time (of which I don't have much) project that's been vaporware for a few years, mainly because I was trying to reach for the moon with DC/DC and DSP and such but with little time to actually spend developing the thing.
Ordered the Bluetooth development PCB last night. Here's the dirtypcbs mockup, went for a blue solder mask for no particular reason. Making everything fit on a 5x5cm PCB took a while, I don't think I can shave a mm off any dimension, but it's done.
This is a development card, final card won't look like this. I'll pick a suitable plastic Hammond box and design the final card to fit inside it.
On the cAMP itself, PCBs are shipped the 1st draft of the firmware is written - fingers crossed it'll fire right up. Making the Digikey order tonight for cAMP parts and bluetooth module parts.
Ordered the Bluetooth development PCB last night. Here's the dirtypcbs mockup, went for a blue solder mask for no particular reason. Making everything fit on a 5x5cm PCB took a while, I don't think I can shave a mm off any dimension, but it's done.
This is a development card, final card won't look like this. I'll pick a suitable plastic Hammond box and design the final card to fit inside it.
On the cAMP itself, PCBs are shipped the 1st draft of the firmware is written - fingers crossed it'll fire right up. Making the Digikey order tonight for cAMP parts and bluetooth module parts.
It would be great if you could leave the ability to pull S/PDIF off the board to feed a mini-DSP and if there were a way to re-name the bluetooth device**.
If that looks like your development board, I'd be happy to buy 2, 5, even 10 raw PCBs to help make that viable.
I took a look at the RN52 license a couple of weeks ago and the per unit fee looked very reasonable but the one time was was not. They might be willing to negotiate something. Also, it looked like you could order various firmwares right from microchip. Did you try that?
**I currently have 3 devices in my house named "Sure HiFi. It is a crap shoot which one I really want to connect to.
If that looks like your development board, I'd be happy to buy 2, 5, even 10 raw PCBs to help make that viable.
I took a look at the RN52 license a couple of weeks ago and the per unit fee looked very reasonable but the one time was was not. They might be willing to negotiate something. Also, it looked like you could order various firmwares right from microchip. Did you try that?
**I currently have 3 devices in my house named "Sure HiFi. It is a crap shoot which one I really want to connect to.
I'll have ~10 prototypes coming, I only plan on building a couple (one for myself, one to send off to Canopy for their evaluation) so I'll definitely have some PCBs left over that you can use.
AAC licensing is $1K upfront for small companies + 98 cents/pop, which is a bit spendy - works out to $11/board in licensing fees if we build 100 boards. The RN52 part #'s that support AptX/AAC also cost a buck more than the plain RN52, bringing us up to $12 extra/board.
Can't find much info on AptX licensing, I'll fire a tweet at CSR and see what happens.
AAC licensing is $1K upfront for small companies + 98 cents/pop, which is a bit spendy - works out to $11/board in licensing fees if we build 100 boards. The RN52 part #'s that support AptX/AAC also cost a buck more than the plain RN52, bringing us up to $12 extra/board.
Can't find much info on AptX licensing, I'll fire a tweet at CSR and see what happens.