BasicMicro - Forums

I would like to change a 25lc256 eeprom to a 25lc1024.

The only differance I can see is that the 1024 has a 24bit address with 7 msb dont care.

Any suggestions on how to implement an address pointer?

The 25256 used

to write a 16-bit address to it.

You need 24-bits, so try

Just make the 7 MSB all zeros. You will have to define "address" as a 32-bit "Long" variable.

There is a forum post that contains the demo code for using an AT25256A EEPROM at
http://forums.basicmicro.net/atomnano-f485/app-note-using-a-32kx8-spi-eeprom-with-atoms-and-nanos-t9163.html
Try using the code in the attached PDF as a guide.

Could not get this to work. Set address to long. When I looked at what was being sent I was getting the bytes in the wrong order.

Address variable MSB on left LSB to the right correct?

------------------------------------Address long var---------------------------------

Address.highbyte.highword _ Address.lowbyte.highword _ Address.highbyte.lowword _ Address.lowbyte.lowword

When I used shiftout.....[address\24] I got

Address.highbyte.highword _ Address.lowbyte.highword _ Address.highbyte.lowword

at eeproms si pin

I looked at using highbyte lowbyte ect.. to send the right bytes



I have not gone to far on this route. It seems like alot of variables are needed. It would be nice to do something like

address_temp = address.highword.lowbyte but I don't thik its possable.

My next aproach was to use 3 bytes and if\then to increment the bytes

So changing your example to this



And adding this
''-------------------------Increments eeprom address by the constant increment--------------------------



And change this to write to the whole eeprom



This works. The way I visualize it is the eeprom is a book. 2 chapters, 512 pages and 256 lines per page.

cntr = chapters (7msb don't care last bit will be a 1 0r 0) chapter 0 pages 0 - 255 or chapter 1 pages 256 - 512
cntr1 = pages (0 to 255 per chapter)
cntr2 = lines (0 to 255 per page)

Have to make sure not to cross page as data will wrap around to line 0 of same page

On a side note I connected the eeprom so that SO and SI share a pin


I have tried this using 5 different Nano pins for SO\SI

P3 - eeprom works
P4 - eeprom works
P5 - eeprom works
P8 - eeprom does not work
P9 - eeprom does not work

Using "Help" from the Studio menu, open the users' manual. Go to page 133. This covers "ShiftIn". It shows a chart with settings that allow the user to change the edge on which the data is latched, and the order of bits sent, ie, LSB or MSB. You figured it out, but this chart may help you figure out how to redefine the command next time you get a device that doesn't agree with a demo code, thus saving you all this hoopla in the future.
Nice job, BTW. We should have you do an app note for this part!
Later.

Just a suggestion but you can access the bytes of a long like this:

address.byte3,address.byte2,address.byte1,address.byte0

So since you needed 24bits of an address you coul dhave just sent

address.byte2,address.byte1,address.byte0

in your shiftout command and just incremented it by address = address + 1

The variable modifiers are:

bit#
lowbit
highbit
nib#
lownib
highnib
byte#
lowbyte
highbyte
word#
lowword
highword

Where # is an appropriate number(eg 0 to 3 for bytes of a long variable)