Teensy 4.0 Breakout Kit

loglow

Well-known member
Hi,

Congrats on the Teensy 4.0 release!

I'm working on a breakout kit for this, and I'd love to get some feedback before producing the first run.

Here's what I've got so far:

Teensy_4_0_Breakout_T.jpg

Teensy_4_0_Breakout_B.jpg

Flex_Cable.jpg

Ok, so here's how this works: The brown board is a small (25 x 11 mm) flex PCB, which can be used either in a direct solder-to-board configuration, or socketed with a connector. I envision the Teensy side of the cable to be almost always soldered directly, but then the breakout side can be a connector when the Teensy is otherwise socketed, or soldered when it's not. The Teensy side of the flex cable can work with a connector too, as long as you're willing to forego the two USB host pins. I don't think I'll include a Teensy-side (8-pin) connector in any kits, whereas a planned socket kit will include a breakout-side (10-pin) connector, so the Teensy can be removed without any soldering.

The breakout is the same size and shape as my existing 3.2 breakout board. The scored "carrier" rails on either side are exactly the same. For space, the larger mounting holes have been removed, and only the mounting holes on the carrier rails remain.

There are pads for a tiny Micro SD card socket. I'm not sure how easy/hard it will be to solder these by hand, so we'll see. If it's impossible to solder by hand, I might offer an option of having it pre-installed for folks who aren't able to do SMD reflow themselves.

The VIN-VUSB switch is the same as it's always been.

There are some new pads on the bottom for a 12 mm coin cell battery!

Also, there are pads for a full-size USB-A connector for the host port, similar to my 3.5/3.6 Standard breakout. I have a question for folks about this though: For USB host power, I was thinking of just passing through VUSB, since the Teensy 4.0 doesn't offer any 5V output. Alternately, I could pass VIN directly as power on the USB host port. Or, should there be some kind of on-board little regulator to provide 5V? Let me know what you think I should do here.

I've never ordered flex boards before, so that should be pretty interesting!

All the best,
Dan
 
That looks nice. I see the USB host pin order like on T_3.6 - except 1 GND in 4 pin format not 5 that PJRC sells? There is a USB Host power $1.56 IC on the T_3.6, that was on the breakouts from PJRC and designed into other boards - having that - or a place for it might be handy. If it goes to a powered HUB that might be safe without it - otherwise Paul has noted USB connect can brownout the Teensy on startup. And if it did have onboard power for 5V USB Host that might help when powered from device USB to T4? That also adds parts and expense.
 
One small thing that I would suggest is moving the ON and Program pins breakout along the outer rows away from the ends and put them so they are aligned with the ground pins. Maybe put ON where pin 24 is, and move 24-28 down one position to the left, and put Program where pin 33 is and move pins 29-33 down to the left. That way it might be easier to attach a tactile switch on each of those pins to turn the Teensy on/off or program it. With your current layout you would have to have the switch go over the mounting hole, which might be problematical for those of us that need to attach (and sometimes remove) the Teensy from other boards. Having the On/Program pins 0.1" or 0.2" away from a ground pin, would allow people to use a standard dupont connector to move the pins off of the board.

I dunno how often people would want to use Serial7, but pins 28 and 29 are on opposite sides of the board.

If you could afford a slightly larger board size, it might be useful have an area to mount at least 3 through hole pull-up resistors between certain pins and 3.3v for i2c and SPI buses. The most important pins are:
  • 18/A4 -- I2C bus 0, SDA
  • 19/A5 -- I2C bus 0, SCL
  • 10 -- Standard CS pin for SPI bus 0

I could imagine also wanting to optionally add pull-up resistors for these pins, but for me these would be a lessor priority:
  • 17/A3 -- I2C bus 1, SDA
  • 16/A2 -- I2C bus 1, SCL
  • 0 -- SPI bus 1, CS
  • 24/A10 -- I2C bus 2, SCL
  • 25/A11 -- I2C bus 2, SDA
  • 36 -- SPI bus 2, CS
 
Looking good!

I'm a little nervous about the soldering of the flex cable and the cost of that part along with the sockets for it.

Did you consider something like this to mate the SD pads:

https://www.digikey.com/product-detail/en/avx-corporation/009258008004062/478-5494-1-ND/2024957

It's a connector that's designed for pcb-to-pcb connection like this. It may have a similar challenge for hand soldering as the SD card slot.

Not sure exactly how to handle the USB host data pins in this case, either with a similar 2-pin connector or a connector like you are planning for pins 24-33.
 
I see the USB host pin order like on T_3.6 - except 1 GND in 4 pin format not 5 that PJRC sells?

Are you talking about the D+, D-, etc. pins in the lower-left of the top image? I could see about rearranging these to match the 5-pin order. Since there are several extra GNDs, there's room for it. Just for reference, the 5-pin order is 5V, D-, D+, GND, GND.

There is a USB Host power $1.56 IC on the T_3.6, that was on the breakouts from PJRC and designed into other boards - having that - or a place for it might be handy. If it goes to a powered HUB that might be safe without it - otherwise Paul has noted USB connect can brownout the Teensy on startup.

I think you're referring to the TPD3S014, am I correct? I can see the utility here for sure, for current limiting and ESD protection, and it might make sense to add it. However, it doesn't do any regulation, and recommends 4.5-5.5V input, a significantly smaller range than VIN's 3.6-5.5V range. But I suppose this setup would make things comparable to the T3.6, which does sound good.

Does it make any sense to have a dedicated 3.3V to 5V boost regulator too, or is that just overkill? Yeah, probably unnecessary.

And if it did have onboard power for 5V USB Host that might help when powered from device USB to T4? That also adds parts and expense.

I'm not sure what you mean here, can you explain further?
 
One small thing that I would suggest is moving the ON and Program pins breakout along the outer rows away from the ends and put them so they are aligned with the ground pins. Maybe put ON where pin 24 is, and move 24-28 down one position to the left, and put Program where pin 33 is and move pins 29-33 down to the left. That way it might be easier to attach a tactile switch on each of those pins to turn the Teensy on/off or program it. With your current layout you would have to have the switch go over the mounting hole, which might be problematical for those of us that need to attach (and sometimes remove) the Teensy from other boards. Having the On/Program pins 0.1" or 0.2" away from a ground pin, would allow people to use a standard dupont connector to move the pins off of the board.

I think this is totally reasonable, and I'll probably make this change for these reasons.

I dunno how often people would want to use Serial7, but pins 28 and 29 are on opposite sides of the board.

Good catch. Not a huge deal, but there's an easy solution: I'll move ON and PG over to the same side and have 28 and 29 next to each other.

If you could afford a slightly larger board size, it might be useful have an area to mount at least 3 through hole pull-up resistors between certain pins and 3.3v for i2c and SPI buses. The most important pins are:
  • 18/A4 -- I2C bus 0, SDA
  • 19/A5 -- I2C bus 0, SCL
  • 10 -- Standard CS pin for SPI bus 0

I could imagine also wanting to optionally add pull-up resistors for these pins, but for me these would be a lessor priority:
  • 17/A3 -- I2C bus 1, SDA
  • 16/A2 -- I2C bus 1, SCL
  • 0 -- SPI bus 1, CS
  • 24/A10 -- I2C bus 2, SCL
  • 25/A11 -- I2C bus 2, SDA
  • 36 -- SPI bus 2, CS

You're right that these would be useful options. I want to keep the same board footprint if possible. However, maybe I'll add pads for 0805 SMD resistors? Hell, maybe there's room for 1206 ones even. These are still very reasonable to solder by hand, and they'll squeeze in much more easily than through-hole ones.
 
I'm a little nervous about the soldering of the flex cable and the cost of that part along with the sockets for it.

Soldering a 1 mm pitch flex cable should be ok. I think. I'm excited to try, at least.

The cost isn't too bad. It's looking like roughly $0.50 per flex board. The connectors are comparable to that. I'm trying to use a flip-lock type that's plentiful in bulk.

Did you consider something like this to mate the SD pads:

https://www.digikey.com/product-detail/en/avx-corporation/009258008004062/478-5494-1-ND/2024957

It's a connector that's designed for pcb-to-pcb connection like this. It may have a similar challenge for hand soldering as the SD card slot.

I did look at some things like this. I don't think the one you linked would be tall enough for a socketed Teensy (about 10 mm of clearance). This is definitely something to play around with and consider if the flex cable route ends up being problematic for any reason.

Not sure exactly how to handle the USB host data pins in this case, either with a similar 2-pin connector or a connector like you are planning for pins 24-33.

A single row of these pads is tricky, since an SMD header has nothing to balance itself against. I also considered pogo pins for the two USB pins, then a special cable with holes for them, or the cable routed around them, but this got weird quickly. A socketed Teensy still needs headers soldered onto it, so I think a small flex cable soldered onto it too would remain reasonable.
 
Hey Daniel, You made my day when I saw this thread! I have a very simple question - I'm sitting here trying see just where the fexible breakout fits into the grand scheme? I can't, for the life of me, see where the pads on either end mate with anything on the T4 :confused: :confused:

Will you be taking pre-orders on Tindie?
 
Perhaps a way to support through-hole resistors while consuming limited board space: Place the holes 0.10 inch apart, allowing the resistors to be placed vertically. There will inevitably be applications where vertical placement is suboptimal. For many of us implementing prototype, hobby or play projects it would work just fine. Those with good vision and eye-hand coordination might be able to place surface-mount resistors between the pads... :)
 
Hey Daniel, You made my day when I saw this thread! I have a very simple question - I'm sitting here trying see just where the fexible breakout fits into the grand scheme? I can't, for the life of me, see where the pads on either end mate with anything on the T4 :confused: :confused:

Will you be taking pre-orders on Tindie?

I can't speak for Daniel (and he likely won't get a T4 for a few days), but if you look at the back picture of the T4 from the order page:

You will see 8 pads labeled DAT1, DAT0, GND, CLK, 3V, CMD, DAT3, DAT2. These are 1mm apart (as opposed to 2.54mm or 0.1" which is normal for through hole soldering). The intention is that these 8 pads would be connected either with a 8x1mm flex connector or the actual flex ribbon, and on the other end you would connect an SD/microSD drive.

There are 2 other pads on the back of the T4, one on either side of the 8 data pads that are offset slightly. I believe these are for soldering the outside of the flex connector, and they aren't electrically connected to anything (but it is easier to solder to a metal connection than the raw PCB).

The beta2 board came with the connector soldered on, and a little flex ribbon. The prototype board that the beta2 board came with had a connector for the flex ribbon and attached it to the microSD card reader (it also had some other features for the audio board, real time clock, and Serial port support).
 
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Perhaps a way to support through-hole resistors while consuming limited board space: Place the holes 0.10 inch apart, allowing the resistors to be placed vertically. There will inevitably be applications where vertical placement is suboptimal. For many of us implementing prototype, hobby or play projects it would work just fine. Those with good vision and eye-hand coordination might be able to place surface-mount resistors between the pads... :)

Or possibly have pads on the bottom similar to the coin cell pads, that are spaced far enough away that you could solder a normal through hole resistor to the pad. It might be problematical if you don't use mounting screws to raise the base of the protoboard up, and you continually move the board and the resistors might get knocked off.
 
Soldering a 1 mm pitch flex cable should be ok. I think. I'm excited to try, at least.

The cost isn't too bad. It's looking like roughly $0.50 per flex board. The connectors are comparable to that. I'm trying to use a flip-lock type that's plentiful in bulk.

I did look at some things like this. I don't think the one you linked would be tall enough for a socketed Teensy (about 10 mm of clearance). This is definitely something to play around with and consider if the flex cable route ends up being problematic for any reason.

A single row of these pads is tricky, since an SMD header has nothing to balance itself against. I also considered pogo pins for the two USB pins, then a special cable with holes for them, or the cable routed around them, but this got weird quickly. A socketed Teensy still needs headers soldered onto it, so I think a small flex cable soldered onto it too would remain reasonable.

Great! I'm excited about this.

Will you be selling the flex cables separately? I'd love to prototype with the whole kit and then use the flex cable to connect to my own main board.
 
Also, there are pads for a full-size USB-A connector for the host port, similar to my 3.5/3.6 Standard breakout. I have a question for folks about this though: For USB host power, I was thinking of just passing through VUSB, since the Teensy 4.0 doesn't offer any 5V output. Alternately, I could pass VIN directly as power on the USB host port. Or, should there be some kind of on-board little regulator to provide 5V? Let me know what you think I should do here.

I think the T3.6 design is a good one to copy here. It provides current limiting, ESD protection and power control for the host port using that TPD3S014.

It's not unreasonable to assume that any T4 that's providing a host port itself would need a 5V supply via VIN or VUSB.
 
Are you talking about the D+, D-, etc. pins in the lower-left of the top image? I could see about rearranging these to match the 5-pin order. Since there are several extra GNDs, there's room for it. Just for reference, the 5-pin order is 5V, D-, D+, GND, GND.
Yes - matching the internal T_3.6 pin count and order would make it map the same - FWIW given onboard USB connector.

I think you're referring to the TPD3S014, am I correct? I can see the utility here for sure, for current limiting and ESD protection, and it might make sense to add it. However, it doesn't do any regulation, and recommends 4.5-5.5V input, a significantly smaller range than VIN's 3.6-5.5V range. But I suppose this setup would make things comparable to the T3.6, which does sound good.
I got this part # from a KurtE post : ‎TPS2055AD‎ shows : 2.7V ~ 5.5V

I'm not sure what you mean here, can you explain further?

About power - OP :
. I have a question for folks about this though: For USB host power, I was thinking of just passing through VUSB, since the Teensy 4.0 doesn't offer any 5V output. Alternately, I could pass VIN directly as power on the USB host port. Or, should there be some kind of on-board little regulator to provide 5V? Let me know what you think I should do
re : 'And if it did have onboard power for 5V USB Host that might help when powered from device USB to T4? That also adds parts and expense.'

Was commenting that a way to get fresh/full 5V power as Host could he handy {VIN or separate supply} - versus sharing what is left of the 5V coming into the Teensy. No single answer - would require added power to the board - in that case a powered hub would act the same and provide more than a single port to the T4. And if the T4 host goes to powered hub - then it wouldn't need the TPD/S# chip either since it wouldn't take power from the T4. Though with onboard full 5V and the power switch chip - it could feed an unpowered hub - or a full power single device.
 
@loglow - if I'm seeing this right: View attachment 17144

The one end hits the SDIO pads on the T4 and passes over the USB Host D+/D- and those pads are all soldered through the holes taking the signals to the far end for offboard use? That looks very cool if it works for a 50 cent flex part!
 
This weekend I will publish the files and docs for the breakout board PJRC made for the beta test. It won't be a product we sell, only shared files and docs on our blog and OSH Park's shared PCB page.

Maybe this info will help?

t4_eval3.jpg
 
This weekend I will publish the files and docs for the breakout board PJRC made for the beta test. It won't be a product we sell, only shared files and docs on our blog and OSH Park's shared PCB page.

Maybe this info will help?
...

Indeed that is a decent and versatile board to work with for so much - with POGO pins and SD ribbon as needed. Only drawback is the headers to audio board mount doesn't move all pins - where they are re-ordered as needed.

I found it very handy when I got first unpinned Teensy 4 to use the long/tall male pins {pins properly seated and the header strip moved to header top} then soldered to the T4 to expose a full length of Male pin above the T4 to put on Female Jumpers to get to all the pins. Then Added male end pins on T4 to get 2nd 3.3V and GND to power second display.

Hopefully to include a good BOM list as a bonus?
 
Based on the feedback already received, you can see a revised pin layout on the breakout image below. VHST would be the output from a TPD3S014. Not entirely sure how I'll handle this as a kit yet though.

I'm sitting here trying see just where the fexible breakout fits into the grand scheme? I can't, for the life of me, see where the pads on either end mate with anything on the T4 :confused: :confused:

The one end hits the SDIO pads on the T4 and passes over the USB Host D+/D- and those pads are all soldered through the holes taking the signals to the far end for offboard use?

Here are two images that should help you visualize how the flex cable will mate with the Teensy (on one end) and the breakout board (on the other). Solder points are marked in red.

Teensy_4_0_Breakout_Flex2.jpg

Teensy_4_0_Breakout_Flex1.jpg

Will you be taking pre-orders on Tindie?

Not going to do pre-orders, but the board/kit will be available for sale as soon as possible.

Will you be selling the flex cables separately? I'd love to prototype with the whole kit and then use the flex cable to connect to my own main board.

Sure, I don't see any reason not to!
 
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Seems to look right. Nice T_3.6 Host pin order. Is that 1.5" x 2.6" overall?

Nice added Flex solder image - it shows as expected on the T4 connect detail.

Question: Would it make sense to add a GND pad spaced with the 'ON' Pin pad to place a button there? In the case the T4's Button is good for PGM usage - being able to add an ON button to the PCB could be handy too:
LogLow_ON.png
 
Here are two images that should help you visualize how the flex cable will mate with the Teensy (on one end) and the breakout board (on the other).

I'd recommend placing the USB host connector closer. The SD signals run at 50 MHz, which is pretty fast and definitely wants GND routed as close together with with CLK as possible. But USB host runs at 480 Mbit/sec, and there's already almost 2 inches of not well impedance controlled routing from the BGA to the end of that flex cable.

Remember to use 2 capacitors for whatever USB current limit chip you choose. Try to resist the typical thinking that bigger must be better. I'd recommend 100 to 150 uF for the output cap, and 2.2 to 4.7 uF for the input cap. If space is an issue, that smaller cap wants to be as close as possible to the current limit chip, and the big output cap wants to be close to the USB connector.

Also a good idea to place a decoupling capacitor close to the SD socket. Those tiny micro SD cards don't have space for much on-board capacitance. Especially if you run the power and ground wires across the board to reach the socket, you really want come capacitance close to the socket.
 
This board seems like an excellent edition to the Teensy 4:) A question: A while ago Frank Bösing made a C64 inside the Teensy 3.6. Is it feasable the teensy 4 can do the same?? it's more powerfull then the 3.6. I'm also wondering if it's possible to implement a hdmi circuit with the teensy 4? With kind regards, Jeroen
 
This board seems like an excellent edition to the Teensy 4:) A question: A while ago Frank Bösing made a C64 inside the Teensy 3.6. Is it feasable the teensy 4 can do the same?? it's more powerfull then the 3.6. I'm also wondering if it's possible to implement a hdmi circuit with the teensy 4? With kind regards, Jeroen

Yes its actually easier than you think. I came across a HDMI shield that can be used with a T3.6 and I adapted it so you can use it with the T4. This is the shield post: https://forum.pjrc.com/threads/54711-Teensy-4-0-First-Beta-Test?p=207850&viewfull=1#post207850

And this is some results: https://forum.pjrc.com/threads/54711-Teensy-4-0-First-Beta-Test?p=208337&viewfull=1#post208337 The testing was done with 10" GoChic display.

Kind of put any further mods on hold because of higher priority testing.
 
This weekend I will publish the files and docs for the breakout board PJRC made for the beta test. It won't be a product we sell, only shared files and docs on our blog and OSH Park's shared PCB page.

Maybe this info will help?

View attachment 17156

Could we please see a photo of that board with Teensy removed? Or really any Teensy test board with pogo pin bed of nails that contact the backside interior so that we can better visualize the end result of the docs. When hand soldering, how do you get all the pogo pins at the right height?
 
Here is a pic - to set the POGO pins I added they were put in place and then the T_4 pressed in place - and they came out usably when soldered from the bottom. Though it is apparent they are not straight in all cases.

20190812_040452rs.jpg
This shows a final Beta board with Ribbon Cable attached for SD pads - covering the USB Host POGO pins - and a white wire Paul soldered to make use of PCB's made before a final version.
 
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