On Wed, 31 Oct 2012 09:40:02 -0400 "Pupic P." ladypupic@gmail.com wrote:
Hi everyone,
I have a MacBook Pro (13" mid-2009) who, I think, suffers from a bad firmware flash : from nowhere, or after an update, it makes 9 beeps when powered on (3 short, 3 long, 3 short) and nothing else. I have found references from similar cases when people seemed to have recovered by rewriting a good firmware with flashrom and buspirate ( http://ho.ax/tag/firmware/). On my machine I have :
- a chip labelled MX25L3205DM2I-12G
- buspirate 3.6 (v3b, firmware 5.10)
- flashrom v0.9.6.1-r1620
- hooked (while the chip still on the motherboard (no power, battery out))
: pin1->CS, pin2->MISO, pin4->GND, pin5->MOSI, pin6->CLK, pin8->3.3v
- Pins 3,7 not connected.
- I also tried pins 3,7,8 together with the same result.
they need to be connected, in this case they need to be set to a distinct potential (namely vcc), but you should always connect all pins of an IC unless noted otherwise in its datasheet. floating pins are evil.
What I get is flashrom ending with : Probing for Generic unknown SPI chip (RDID), 0 kB: RDID byte 0 parity violation. probe_spi_rdid_generic: id1 0x00, id2 0x00 Found Generic flash chip "unknown SPI chip (RDID)" (0 kB, SPI) on buspirate_spi. Probing for Generic unknown SPI chip (REMS), 0 kB: probe_spi_rems: id1 0x0, id2 0x0 Found Generic flash chip "unknown SPI chip (RDID)" (0 kB, SPI).
Any idea why?
this means that MISO is always read as low. this can have a number of reasons. one of example is that pin8 is also connected to a number of other components that need more power than the bus pirate (or whatever) can deliver. see also http://flashrom.org/ISP