Possible Ways to Brick?

RE: Possible Ways to Brick?

Nick — Thu, 21 Jul 2016 23:01:21 GMT

I have a JLink as well so I will give this a try. It appears that we are seeing the same thing over two of their products. Maybe their bootloader is doing something to the NVM that it shouldn't be...

RE: Possible Ways to Brick?

F800 — Thu, 21 Jul 2016 22:53:18 GMT

We can reprogram the chip, using RF Digital's programmer. We can connect Nordic's Dev Kit to the board and verify that the device is able to respond' to JLink commands. What we cannot do is successfully execute Simblee code that appears to load correctly with RF Digital's programmer. I've even taken that one-way-ticket to erase one failing device's FLASH using the Nordic/JLink and verified that JLink can load/verify/execute good code. I conclude that the nRF51822(s) are functional but that something is corrupting either the RF Digital code or the SoftDevice. Since the Simblee is locked, however, I can think of no fix that does not erase the FLASH and that leaves us with a 'bricked' Simblee.

RE: Possible Ways to Brick?

mstrouse — Thu, 21 Jul 2016 16:24:34 GMT

See the following forum post ... at the bottom of the first entry there should be a link to a PDF showing the JLink connections to an RFDuino or RFD22301 module. At least you can check to see if the module / nRF51 is still alive. Note that since the readback protection is probably set, you'll have to get creative in how far you can go to interrogate the part.

forum.rfduino.com/index.php

RE: Possible Ways to Brick?

Carl — Thu, 21 Jul 2016 14:25:13 GMT

We're seeing similar problems and hopefully we can help each other. We're working with RFDigital's newer chip Simblee and have a similar problem bricking modules that you're seeing with the RFDuino. We have a few that appear to have the RFDigital bootloader corrupted. We can use Nordic tools to connect and program the chip, but can no longer use the arduino tools. We have another one that we can program with arduino tools just fine but it won't run any code. I don't know if the actually execute portion of that chip's bootloader was corrupted or maybe the soft device was corrupted? Are you able to update code on your bricked modules? If you're able to figure anything else out, we'd appreciate it if you could let us know. Thanks.

RE: Possible Ways to Brick?

Øyvind Karlsen — Wed, 20 Jul 2016 07:15:56 GMT

Ok, sorry about the voltage confusion.

Normally I would read the SWD interface, but this does not seem to be routed out on the RFduino. The reset pin on nRF51 is active low, I am unsure what is the case for your module. Probably RFduino support will have a lot of these answers ready for you.

RE: Possible Ways to Brick?

Nick — Tue, 19 Jul 2016 19:53:00 GMT

Yes I am fully aware of how linear regulators work. The nominal battery voltage is between 6v (when it is dead) and more than 8v when fully charged. There is always enough headroom for the 3v LDO and the 5v LDO and the variable 0v-5.5v buck.

I have also looked at it with a lab supply. When the input voltage is decreased, the LDO output voltage tracks downwards with the input until about a diode above ground where it just dies. All perfectly normal.

I also would have no problem with the Nordic chip not working properly when the input voltage gets too low. However, once normal voltage is applied again, it should work again. Right now, it seems like 20% of the time (4/20) the part stops functioning when the voltage gets low (that's OK) but then on the next power cycle when the input voltage is good, it never boots up.

That's what I am trying to figure out, is what could cause the part to not boot up, and what can I probe to see if it is booted. Is there a signal it puts out on the chip antenna to check connectivity that will show up with a scope? Does the reset pin or some other pin have some discernible pattern before, during, or after boot up? Test mode pins?

RE: Possible Ways to Brick?

Øyvind Karlsen — Tue, 19 Jul 2016 09:10:12 GMT

Did you heed the following sentence from the MCP1802T datasheet?

The minimum VIN must meet two conditions: VIN>=2.0V and VIN >=(VR + 1.0V). Where VR is the output voltage.

I'm not sure of the workings of this particular LDO, but could it be possible that it enters an unspecified state when the input voltage gets low?

Could you try probing the output voltage from the MCP1802 device?

Best regards,

Øyvind

RE: Possible Ways to Brick?

Nick — Tue, 19 Jul 2016 08:38:45 GMT

Current LDO is a Microchip MCP1802T-3002I. Good for 10V max input, 300mA max output. The ONLY things hooked up to the +3v supply is the RFDuino and a 4-IO I2C expander (PCA9536TK,118). Previously when this happened everything was supplied by the +3.3v 1.5A SMPS.

Yes the LiPo goes down to 2.8v and is dead, correct. That is exactly what is being tested, dead batteries. However I have completely 100% disconnected the battery and it is being powered by a Keithley 2602B SMU ($10K USD). With the input voltage at 8.2v or any voltage for that matter, the RFDuino is completely unresponsive.

All other circuitry is operational. There is an additional 5v LDO and an LTC3883 with full telemetry capabilities, all are operational.

RE: Possible Ways to Brick?

Øyvind Karlsen — Tue, 19 Jul 2016 08:23:44 GMT

The Li-Po voltage is 2.8 V? Then that Li-Po is dead.

What voltage range is your LDO rated for, do you have a product sheet for reference?

RE: Possible Ways to Brick?

Nick — Tue, 19 Jul 2016 08:00:25 GMT

And yes I have tried with my lab supply and they do not turn on again. Out of about 20 parts, we have had 4 fail in this way which is very concerning. As far as I know, I am not doing anything that the datasheet says it cannot handle.

Yes by "brick" I mean non-recoverable fault. I have received the code and there are no writes to the flash memory at all. So back to no idea why these would fail.

Are there any signals that are probe-capable on the output that will show it completed a POR? Like measuring a node for something internal to connect? A small change in an output voltage when a programmed trim value gets loaded, etc? I would like to prove that the RFDuino or Nordic device is powering up and completing a POR or not and bricked. All other aspects of the circuit work perfectly.

RE: Possible Ways to Brick?

Nick — Tue, 19 Jul 2016 07:54:26 GMT

Hello,

Correct that they do not turn on again. No signs of life.

The battery can take 30W draw. Yes 30W, not mW, it is a gigantic Li-Po battery. On previous designs the RFDuino (Nordic part) was powered via a 3.3v SMPS buck capable of 1.5A continuous. We saw 3 parts die in this manner and it was suggested we power it from 3.0v. The SMPS has tighter than 1% regulation as measured by a high end Agilent scope, there were no spikes, very minimal ripple even under full load. Now with the LDO, it is an exact 3.000v with 4.7uF hanging off the LDO output and another 4.7uF right next to the RF chip.

The battery is nominally 7.2v (2 series lithium). When the battery gets very low, down to 2.8v after a total deep discharge sometimes the RF chip never recovers. The battery charges back up to 8.4v no problems. But the RFDuino is no longer discoverable. An LED hooked up to blink, never blinks.

RE: Possible Ways to Brick?

Øyvind Karlsen — Tue, 19 Jul 2016 07:17:46 GMT

Hi,

What do you mean by brick, do these devices not turn on again when powered by lab power supplies?

Are you sure that the battery can take the approx 15 mA current spikes (radio TX + cpu active)? You can alleviate this somewhat by adding capacitor reservoirs on the VDD line.

What is probably happening is that your battery is being pulled down from 2.8V by a radio TX current draw, the battery voltage will drop due to not being able to supply the instantaneous current. At 2.8V a coin cell battery is typically at the end of its life.

Best regards,

Øyvind