[flashrom] Problem while erasing chip prior write bin file.

Nico Huber nico.h at gmx.de
Tue Mar 6 23:13:22 CET 2018

On 06.03.2018 22:13, Luca Bacci Bonotti wrote:
> In your opinion is better the raspberry pi or ch341a to reach my goal?

I don't know. I doubt it makes much of a difference. If one fails, you
can try the other. Though, the RPi is much faster.

> Should I buy a breadboard for create better connections ?

Better than what?

> Can you draw a schematic that I can follow?

Sigh, I guess I can.

Programmer         SPI Flash

  /CS   ------------  /CS

  MISO  ---50-Ohm---  MISO

  GND   ------------  GND

  MOSI  ------------  MOSI

  CLK   ------------  CLK

  VCC   ------------  VCC
         `-10kOhm--- /WP
           `-10kOhm- /HOLD

This is about the minimum setup I'd use for a plain (unsoldered)
chip. Resistor ratings may vary.


> Il 6 mar 2018 21:55, "Nico Huber" <nico.h at gmx.de> ha scritto:
>> Hello Luca,
>> On 06.03.2018 07:25, Luca Bacci Bonotti wrote:
>>> I tried with chip soldered and unsoldered. Same results.
>> same results? probably due to very different problems. Especially when
>> the chip is not part of a circuitry (that might already take care), you
>> have to connect all input pins of the chip. Also, very often, a series
>> resistor at least on the MISO output is required.
>>> I previously tried programming with raspberry PI but it was unable to see
>>> my chip.
>>> I have both CH341A and Raspberry Pi.
>> When you use the Raspberry Pi, make sure you set the `spispeed` parame-
>> ter of linux_spi to something reasonable (I'd start trying around 1000,
>> i.e. 1MHz), the default is OS dependent and often not reliable.
>>> Where should i connect /HOLD /WP on the CH341A ?
>> /HOLD should be pulled up towards VCC (i.e. using a series resistor,
>> 10kOhm maybe), state of /WP usually only matters when the chip has some
>> write-protection set up, so either pull up towards VCC or down towards
>> GND (if in doubt, up).
>> Nico

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