Diy teensy sdram solder yourself

T

theboot900

Well-known member
I've designed a DIY Teensy 4.1 based board with Sdram with the idea of being able to solder it yourself. (It requires a stencil and solder paste as well). I don't have a hot plate, so i have been heating them with hot air from underneath. It uses the BGA 12x12 chip. Like dog bones board it uses the teensy micromod sized flash chip.

  • No special manufacturing. $4 for 5 boards from jlcpcb
  • Excel file with complete component listing, quantities and Links to all required components on mouser.
  • Full schematic, Kicad board and Gerber files
  • Printable PDF showing all components placings for easy reference when placing parts.
  • Small form factor. Same length as teensy 4.1. 20mm wider than teensy 4.1.
  • Smallest component is 0603
  • All but 2 components are on one side of the board. 2 capacitors will need to be hand soldered afterwards.
  • 60 IO pins exposed
  • GPIO7 - all 32 bits exposed
  • GPIO6 - upper 16 bits exposed
  • 32mb Sdram using dogbones sdram library.
  • Sd card
  • Full part listing with quantities and mouser links for parts
  • Can be powered by Usb 5v. Or remove the bridge from Usb to voltage regulator and it can be be powered exclusively through 3.3v pin (recommended to use a linear 3.3v input supply)

Possibly due to my routing (I had trace lengthed them) the Sdram runs fine overclocked at 198mhz, but at 220mhz overclock it gets some errors. I'm only a hobbyist and this is the first 4 layer board i've done. Maybe someone will find it useful.

All the files are at https://github.com/theboot999/Teensy-DIY

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Is there an external 5V pin, to power it from an external 5V supply or power connected devices that require 5V?
 
No you would have to route one yourself. I didn't have any use for one and initially was just going to be 3.3v only. I added 3.3v regulator to be able to power of 5v usb.
 
Happy to see that you were successful in making your own SDRAM board after me and @Rezo started the endevour to make it happen, and managed to get a full list of people (you know who you are) to join in and make it reality. This is what a community should be.

Stay creative people! 😁
 
Dogbone06 said:
Happy to see that you were successful in making your own SDRAM board after me and @Rezo started the endevour to make it happen, and managed to get a full list of people (you know who you are) to join in and make it reality. This is what a community should be.

Stay creative people! 😁
Click to expand...

Thanks! Definitely wouldn't have been able to do it without you and rezo
 
Regarding "only 198MHz" in your text above. Did you use a 10pF for the SDRAM?
We found that 10pF seemed to work best, we reached 227MHz (if I am not mistaken) stable. And at 240MHz it started to not work to well.
Defragster did see other results with 12pF but we concluded that it must be more/less solder which creates capacitance and thus giving slightly different results. As these capacitors were soldered by hand.

So if you don't have a 10pF for the SDRAM cap, try that and see if you can reach the 227 mark.
 
Dogbone06 said:
Regarding "only 198MHz" in your text above. Did you use a 10pF for the SDRAM?
We found that 10pF seemed to work best, we reached 227MHz (if I am not mistaken) stable. And at 240MHz it started to not work to well.
Defragster did see other results with 12pF but we concluded that it must be more/less solder which creates capacitance and thus giving slightly different results. As these capacitors were soldered by hand.

So if you don't have a 10pF for the SDRAM cap, try that and see if you can reach the 227 mark.
Click to expand...
It's there at C11. But it could be a case of the value having to match the design; we found 10pf to be best, but the layout on this board looks a little bit different and also seems to use different size components.
 
jmarsh said:
It's there at C11. But it could be a case of the value having to match the design; we found 10pf to be best, but the layout on this board looks a little bit different and also seems to use different size components.
Click to expand...
Yeh, I guess this is the best that can be done, and 198 is still decent when considering that the SDRAM is rated for 166.
 
theboot900 said:
I've designed a DIY Teensy 4.1 based board with Sdram with the idea of being able to solder it yourself. (It requires a stencil and solder paste as well). I don't have a hot plate, so i have been heating them with hot air from underneath. It uses the BGA 12x12 chip. Like dog bones board it uses the teensy micromod sized flash chip.

  • No special manufacturing. $4 for 5 boards from jlcpcb
  • Excel file with complete component listing, quantities and Links to all required components on mouser.
  • Full schematic, Kicad board and Gerber files
  • Printable PDF showing all components placings for easy reference when placing parts.
  • Small form factor. Same length as teensy 4.1. 20mm wider than teensy 4.1.
  • Smallest component is 0603
  • All but 2 components are on one side of the board. 2 capacitors will need to be hand soldered afterwards.
  • 60 IO pins exposed
  • GPIO7 - all 32 bits exposed
  • GPIO6 - upper 16 bits exposed
  • 32mb Sdram using dogbones sdram library.
  • Sd card
  • Full part listing with quantities and mouser links for parts
  • Can be powered by Usb 5v. Or remove the bridge from Usb to voltage regulator and it can be be powered exclusively through 3.3v pin (recommended to use a linear 3.3v input supply)

Possibly due to my routing (I had trace lengthed them) the Sdram runs fine overclocked at 198mhz, but at 220mhz overclock it gets some errors. I'm only a hobbyist and this is the first 4 layer board i've done. Maybe someone will find it useful.

All the files are at https://github.com/theboot999/Teensy-DIY

View attachment 37454View attachment 37455View attachment 37456
Click to expand...

Very very cool project!
What have you done with it so far? Anything interesting with the additional GPIOs and SDRAM?
 
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jmarsh said:
It's there at C11. But it could be a case of the value having to match the design; we found 10pf to be best, but the layout on this board looks a little bit different and also seems to use different size components.
Click to expand...

Yes I tried a 10pf and a 6pf.

But ive put it down to my lack of professional routing skills. And also in trying to keep power filtering capacitors all to one side of the board they would not be optimally placed.
 
theboot900 said:
Yes I tried a 10pf and a 6pf.
Click to expand...
On the @Dogbone06 board I tried 6 (6.5?) up over 12 and the one board I had did better with 12 - but 10 was a good sweet spot on that layout for the other boards together all going a bit over 200 MHz - and some over the 220 as noted.

Indeed, CAP location seems important - PJRC wanted them on the close to MCU on bottom - and then others to balance the build. But if it is working, you did well.
 
defragster said:
On the @Dogbone06 board I tried 6 (6.5?) up over 12 and the one board I had did better with 12 - but 10 was a good sweet spot on that layout for the other boards together all going a bit over 200 MHz - and some over the 220 as noted.

Indeed, CAP location seems important - PJRC wanted them on the close to MCU on bottom - and then others to balance the build. But if it is working, you did well.
Click to expand...

Thanks. I'll try a bunch of different values and see if I can get an improvement. It's always bits 8 to 15 that error out (when reading the 32 bit words)
 
From memory, we managed to get 200MHz with no cap at all just leaving the trace disconnected - have you tested what the maximum safe speed is for that case? It may be higher if the trace is longer.
 
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