"VREG TOO LOW, is there a short?"

Hacking multi-tool. Get one for $30, including worldwide shipping.

"VREG TOO LOW, is there a short?"

Postby Coldblackice » Sat May 12, 2018 7:02 pm

I'm receiving this error, despite the self-test reporting everything as working/fine. I have the pirate hooked up to a BIOS chip, trying to talk with it over SPI.

Any ideas? I have a v3b sandbox electronics version, v7.1 firmware and v4.5 loader. Really frustrated trying to figure this out! Any help would be greatly appreciated
User avatar
Coldblackice
Newbie
Newbie
 
Posts: 31
Joined: Wed Mar 21, 2012 1:05 am

Re: "VREG TOO LOW, is there a short?"

Postby USBEprom » Sun May 13, 2018 4:31 am

Hi Coldblackice.
How are you supplying power to the chip?
The 3.3volt and 5volt on-board power supplies inside the Bus Pirate can provide up to 150mA so that it can not feed the whole mainboard but the chip of the BIOS alone only.
If not already done, you must to switch on the mainboard while operate on the chip via the Bus Pirate, taking care not to connect the positive power supply (3.3V or 5.5V) of the BusPirate to the pin +Vcc of the BIOS chip.
You must use only MISO, MOSI, CLK, CS and GND, possibly activating the pull-up resistors if necessary.
Maybe this will fix your problem.

Be seeing you.

U.Sb
USBEprom
Full Member
Full Member
 
Posts: 148
Joined: Wed Mar 14, 2012 4:09 pm

Re: "VREG TOO LOW, is there a short?"

Postby Coldblackice » Wed May 16, 2018 3:54 pm

Thanks USB, I appreciate it. Good to know about the 150mA. And also good to know about the possibility of relying on a mainboard to power a chip, and then tapping into it with a Bus Pirate while it's getting powered from its host. In my current situation, I have the chip fully removed from the board by itself, but that's something I'll have to try in the future for curiosity (and for future potential chips/projects).

That being said, correct, I do currently have the BIOS chip removed from the mainboard and attached to the Bus Pirate alone. I seem to have found a solution, though I'm not sure if this is a sign of damage: if I keep trying to turn on the power supply a few times in a row, it eventually turns on.

Any idea why this might be? Sometimes it takes two W's, and I believe other times 3. I hope I haven't unintentionally bypassed a protection mechanism by doing this and potentially damaged either the chip or the Bus Pirate :/

Code: Select all
Ready
SPI>W
VREG too low, is there a short?
POWER SUPPLIES OFF
SPI>W
POWER SUPPLIES ON
Clutch engaged!!!
SPI>v
Pinstates:
1.(BR)  2.(RD)  3.(OR)  4.(YW)  5.(GN)  6.(BL)  7.(PU)  8.(GR)  9.(WT)  0.(Blk)
GND     3.3V    5.0V    ADC     VPU     AUX     CLK     MOSI    CS      MISO
P       P       P       I       I       I       O       O       O       I
GND     3.33V   4.85V   0.00V   0.00V   L       L       H       H       L



And for reference:

Code: Select all
SPI>i
Bus Pirate v3.b clone w/different PIC
Community Firmware v7.1 - goo.gl/gCzQnW [HiZ 1-WIRE UART I2C SPI 2WIRE 3WIRE KEYB LCD PIC DIO] Bootloader v4.5
DEVID:0x044F REVID:0x3043 (24FJ64GA00 4 B5)
http://dangerousprototypes.com
CFG1:0xF9DF CFG2:0x3F7F
*----------*
Pinstates:
1.(BR)  2.(RD)  3.(OR)  4.(YW)  5.(GN)  6.(BL)  7.(PU)  8.(GR)  9.(WT)  0.(Blk)
GND     3.3V    5.0V    ADC     VPU     AUX     CLK     MOSI    CS      MISO
P       P       P       I       I       I       O       O       O       I
GND     3.33V   4.84V   0.00V   0.00V   L       L       L       L       L
POWER SUPPLIES ON, Pull-up resistors OFF, Open drain outputs (H=Hi-Z, L=GND)
MSB set: MOST sig bit first, Number of bits read/write: 8
a/A/@ controls AUX pin
SPI (spd ckp ske smp csl hiz)=( 1 0 1 0 0 1 )
*----------*


(I'm using a Sandbox Electronics authorized clone. I was a student with very little money at the time, otherwise I would've bought the normal version!)
User avatar
Coldblackice
Newbie
Newbie
 
Posts: 31
Joined: Wed Mar 21, 2012 1:05 am

Re: "VREG TOO LOW, is there a short?"

Postby USBEprom » Thu May 17, 2018 12:59 pm

Hi Coldblackice.
I understood the matter.
Anyway, I don't konw exactly how it is the Sandbox Electronics authorized version, if the same as the original project or not (seems to me the PIC is different), but the on board power supply should be protect from short circuit and from the overload, so nothing should have failed.
From what you wrote it is like the current drawn from the chip exceeds the maximum that the imbedded power supply can provide or that the latter has problems.
In order to be sure you should understand what is the current limit for your clone from Sandbox Electronics, though.
However from the two tables you wrote all seems to be fine.
You could check the whole thing by using the selftest procedure of the Bus Pirate, Sandbox Electronics version too should allow it.
However, this would not exclude problems with the power supply inside the device.
In order to check it, please stage try looking here:

viewtopic.php?t=5249&p=50828#p54182

Good luck!

Be seeing you.

U.Sb
USBEprom
Full Member
Full Member
 
Posts: 148
Joined: Wed Mar 14, 2012 4:09 pm


Return to Bus Pirate Support

cron