How to read & write to a 25aa1024 (1 Mbit SPI Bus Serial EEPROM) via 16F88

[mackrackit]

SHIFTIN/SHIFTOUT should work for the 25aa1024. You will need to look at the data sheet for the correct modes and all of that stuff.

This page has a few example about SHIFTIN/OUT and SPI.
http://www.melabs.com/resources/samples.htm

[wolwil]

SHIFTIN/SHIFTOUT should work for the 25aa1024. You will need to look at the data sheet for the correct modes and all of that stuff.

This page has a few example about SHIFTIN/OUT and SPI.
http://www.melabs.com/resources/samples.htm

Thanks for the heads up! I don't know how I missed that sample ,the "spix.bas" to begin with. I guess I just had to scroll down a little more :/

Seeing how I dont have the time to find this out for a few days... what chip should I expect to be quicker the I2C or the SPI? Both will be running off of a 4 MHz clock.

[mackrackit]

I do not know which is faster, never did a side by side or studied the specs for that.
Let us know what you find. It will be interesting to see.

[wolwil]

I made my address a WORD because the 24AA1025 (1024K I2C™ CMOS Serial EEPROM) has a 2 byte address. So in theory this should work but as you can see the output is reading "0" in every address when it should be reading "5"

Does my code look right?

I am unsure of the PAUSE 10ms as I can't find any specs in the data sheet for the amount of time needed after each WRITE cycle. I tried commenting out the delay but still the same results. One would think if the delay was wrong I would still get a "5" in Addr0 at the very least.

Here is the schematic I used to wire up the 24AA1025 to my 16F88:
http://melabs.com/resources/pbpmanual/5_30-5_31.htm

Here is the code:

SO      con     0                       ' Define serial output pin
T2400   con     0                       ' Set serial mode
DPIN    var     PORTA.0                 ' I2C data pin
CPIN    var     PORTA.1                 ' I2C clock pin
B0      var     WORD                    ' Address
B1      var     byte                    ' Data from first address read
B2      var     byte                    ' Data from second address read
B3      var     byte                    ' Second Address

   For B0 = 0 To 15                                    ' Loop 16 times
      I2CWRITE DPIN,CPIN,$A0,B0,[5]                    ' Write a "5" to each location
      Pause 10                                         ' Delay 10ms after each write
   Next B0

loop:  
 
   For B0 = 0 To 15 step 2                                          ' Loop 8 times
   high 3                                                           ' LED on to signify a Read in progress
      I2CREAD DPIN,CPIN,$A0,B0,[B1,B2]                              ' Read 2 locations in a row
      B3 = B0 + 1                                                   ' Create second address for print
      Serout SO,T2400,["Addr",#B0,":",#B1,13,10,"Addr",#B3,":",#B2,13,10]  ' Print 2 locations
      B3 = 0                                                        ' Zero out B3 Variable
   low 3                                                            ' LED off to signify no read in progress
   Next B0

   Serout SO,T2400,[13,10]             ' Print linefeed
 
   Goto loop

And here is what I get on Hyperterm:

Addr0:0       
Addr1:0       
Addr2:0       
Addr3:0       
Addr4:0       
Addr5:0       
Addr6:0       
Addr7:0       
Addr8:0       
Addr9:0       
Addr10:0        
Addr11:0        
Addr12:0        
Addr13:0        
Addr14:0        
Addr15:0

[wolwil]

I simplified everything and have tried everything (even tried swapping out the chip) but I cant get this EEPROM to write anything to it. Here is the new simplified code:

SO      con     0                           ' Define serial output pin
T2400   con     0                           ' Define serial mode
cont    CON     %10100000                   ' Define Control byte
addr    CON     %0000000000000111           ' 2 Byte Address of 7
B1      VAR     BYTE                        ' Var for data being read

I2CWRITE PORTA.0,PORTA.1,cont,addr,[1]      ' Send the byte 1 to address 7

PAUSE 10                                    ' Wait 10ms for write to complete

I2CREAD PORTA.0,PORTA.1,cont,addr,[B1]      ' Read address 7 into B1

Serout SO,T2400,["Addr",#addr,":",#B1,13,10] ' Print B1's Value in DEC

Correct me if I'm wrong but the above code should work but it still just reads "0" in hyperterm like this: "Addr7:0"

I am reading 4.97V from pins 4-8 and I get 4.82V from 4-5 and 4-6 on the 24FC1025 EEPROM so my voltage is within specs. I have checked all continuity on the circuit and they all tone out.

I don't know what else to do. Please help.

[wolwil]

Pin A2 needed to be tied to VCC not VSS in order for the chip to be enabled. This however has not fixed my problem I am still getting nothing written to it.

[wolwil]

I believe I have the SDA and SCL pins going to the wrong pins on the 16F88. I have them right now going to PORTA.0 for SDA and PORTA.1 for SCL. I believe they need to be set as PORTB.1 for SDA and PORTB.4 for SCL with the 16F88. I will try this tonight and post my findings.