PCB v3.3a

[Seth]

https://oshpark.com/shared_projects/fXRUAxSj

Updates in this pcb from 3.2:
- added exposed ground layer around border to top and bottom to hopefully prevent ESD issues.
- added dedicated pin and resistor/capacitor from 328 to rn52 power enable pin to allow power down of Bluetooth for future power savings (not implemented yet).
- added lots of silkscreen labeling.
- added jumper to force 9600 baud instead of 115200.
- board size is now almost *exactly* 62mm square (2.44").
- added resistor divider network to allow software to identify which rev of hardware is being used (not implemented yet).

[Viggen]

Hey I just put together my first Adapter using this board and had a few questions....

I ordered the parts list from Mouser for the older versions of the boards that didn't have these updates so I'm missing a couple of pieces and want to figure out what I should order. From the printing on the board it looks like the added R15 is 10K, C10 is 0.1uF, R14 is 100k, but I don't see anything for R13 or the 9600_EN jumper. Can anyone tell me what is supposed to go in the last two spots?

I luckily have some spares so I can fill C10 and R15, but R13 just says 'Revision' and I'm not sure what if anything I'm supposed to put on the 9600_EN jumper or if that is for future use too...

Thanks!

[Seth]

Sorry for the lack of BOM update; that totally slipped my mind  I just updated the BOM.

The Revision resistor (R13) and R14 are irrelevant right now; they haven't been implemented in code yet (that I know of). They are for future use, for software to be able to read the voltage level of that resistor divider network, and let the software make changes as necessary per that pcb. So for example, if (when?) v3.4 of pcb comes out and we had to make a change, the software can poll pin A1, and if it reads a specific value, turn a pin high, vs if it reads a different value, turn a pin low. So right now you don't need to populate R13 or R14.

For C10, it should be 0.1uF and R15 is 10k, but again, these aren't being used (yet) in software, but they will be soon; this resistor/capacitor (RC) network is used to generate a clean 3.3v signal out from the 328 digital 9 pin, to turn on the RN52 Enable pin. without this, the RN52 will never turn on. So without a software update (and C10/R15), the v3.3A pcbs won't work (don't worry, Karlis is on it :)

In the meantime, you can always short the PWREN pin to the 3.3 line to force the RN52 to always being on (which is what all other pcb revisions do right now).

[Viggen]

No problem, I appreciate all the work you guys are doing on this!

So if I understand correctly, and thats a big if, I could add C10 and R15 as they'll be used in the next round of software updates, and maybe worry about R13 and R14 down the road? Is the 9600_EN pad included with R13/14, in that I don't have to do anything about it just yet?

Sorry for all the stupid questions, I'm very new to all this stuff and I'm trying to learn on the fly.

[Seth]

Viggen wrote

No problem, I appreciate all the work you guys are doing on this!

So if I understand correctly, and thats a big if, I could add C10 and R15 as they'll be used in the next round of software updates, and maybe worry about R13 and R14 down the road? Is the 9600_EN pad included with R13/14, in that I don't have to do anything about it just yet?

Sorry for all the stupid questions, I'm very new to all this stuff and I'm trying to learn on the fly.

Yes, adding C10/R15 now won't hurt anything, but will be needed when the software changes arrive.
R13/R14 are not needed at all right now; they are for future use.
The 9600_EN pads are there so that you can short them and force the rn52 into 9600 baud instead of the default 115200 baud (in case there's an issue for whatever reason at 115200).

[Da Bear]

Have only took a quick peek at the new board, not some extreme changes so it should be possible to rebuild my 3.2 to 3.3a? It wont look pretty, but as long as it's doing what it should do ;)

[Seth]

Da Bear wrote

Have only took a quick peek at the new board, not some extreme changes so it should be possible to rebuild my 3.2 to 3.3a? It wont look pretty, but as long as it's doing what it should do ;)

The only thing that you won't be able to do with the 3.1 pcb is turn off the rn52. on 3.2+ boards, there is a separate signal that needs turned on via software (and needs c10/r15) to hit the rn52 with the power on signal. there are other minor tweaks/changes, but that's the biggest one. you should be fine.

[Viggen]

se4587 wrote

The 9600_EN pads are there so that you can short them and force the rn52 into 9600 baud instead of the default 115200 baud (in case there's an issue for whatever reason at 115200).

Ok two more n00b questions, is there a reason for/against running at 9600 baud? Have there been issues at 115200, or is it just preventative maintenance? I jumped the two pads but wasn't really sure if I needed to do so

And then I've been itching to see if I've assembled this properly, if I'm reading your earlier post correctly I can jumper the PWREN and 3V3 pads so the RN52 is powered up. Can I then run the old software on this PCB or is it a no go without the new software (in which case I won't bothering jumping them)?

[Karlis]

Viggen wrote

Ok two more n00b questions, is there a reason for/against running at 9600 baud? Have there been issues at 115200, or is it just preventative maintenance? I jumped the two pads but wasn't really sure if I needed to do so

By default, RN52 bluetooth chip uses 115200bps, that's the reason we chose to go with this baud rate. However, during some extensive tests performed recently, I noticed that when we communicate with RN52 via ATMEGA328, the signal becomes more "bell-shaped" => very bad. :) I stepped down the code to use 9600bps and now the signal is nice and square. As it should be. So long story short - 9600bps is the way to go. I've implemented the changes in the code already and have uploaded them to Github.

Viggen wrote

And then I've been itching to see if I've assembled this properly, if I'm reading your earlier post correctly I can jumper the PWREN and 3V3 pads so the RN52 is powered up. Can I then run the old software on this PCB or is it a no go without the new software (in which case I won't bothering jumping them)?

Yes. By shorting PWREN with 3V3 pins you'll get the RN52 in "constantly on" state. Which is also the case for all hardware revisions prior 3.3A. We had some issues with enabling the power "on demand" using previous bluetooth chips, that's why we opted to go with "constantly on" option. Now with 3.3A hardware revision we'll be able to put RN52 to sleep and wake it up when needed.

[Viggen]

Great, thanks again for the work you guys are doing on this! I wish I had any sort of coding or electrical engineering skill to help out....

I'll download the new code and upload it when I'm home tonight and let you know if I run into any issues.

[homerisback]

Hi there,
I dig up this topic because I've been sent a v3.3 module soldered by an inexperienced saabist that didn't worked at all... and for good reason, there were shortcuts all around RN52, MCP2515, diodes and LEDs upside down, etc.
I've been able to bring the RN52 back to life and cleanup every bad soldering but a chip didn't stand the treatment : IC3 voltage regulator which was a Micrel 5209 3,6V series on this pcb.

Should I replace it with the same chip or can I use the one used on the latest PCBs (i.e. NCP1117ST33T3G) delivering 3,3V ?

Thanks guys

[Seth]

No! I'm pretty sure the footprints for these chips are different; double check the data sheets before you do that. The 3.6 doesn't hurt anything since the voltage goes through the diodes; its closer to 3.3-3.4v

On Sat, Jan 14, 2017 at 13:37 homerisback [via BlueSaab Forum] <[hidden email]> wrote:

Hi there,


I dig up this topic because I've been sent a v3.3 module soldered by an inexperienced saabist that didn't worked at all... and for good reason, there were shortcuts all around RN52, MCP2515, diodes and LEDs upside down, etc.


I've been able to bring the RN52 back to life and cleanup every bad soldering but a chip didn't stand the treatment : IC3 voltage regulator which was a Micrel 5209 3,6V series on this pcb.



Should I replace it with the same chip or can I use the one used on the latest PCBs (i.e. NCP1117ST33T3G) delivering 3,3V ?



Thanks guys

---

If you reply to this email, your message will be added to the discussion below:

http://bluesaab-forum.2349123.n4.nabble.com/PCB-v3-3a-tp222p922.html

To start a new topic under Hardware, email [hidden email]


To unsubscribe from Hardware, click here.


NAML