Trouble with Kent's I2C Eeprom routine

[Anonymous]

Hello all,

Per Kent's advice, this is a new but related thread on his eeprom routine. Here's the set-up. I have a toggle switch on A.0. In one position, reading from the 24LC256 is demoed, in the other position writing to the chip is demoed (always after a restart power-up).

The results appear on serial terminal software. When writing to the eeprom, I have the terminal software send one character at a time, with a 50 mS pause between each.

Here's the trouble: reading the eeprom always works, but writing to it always sends the same garbage. I had previously done a similar project with similar source code on a PICAXE which worked flawlessly. Here's my GC Basic code. I hope it formats halfway decently on this forum:

;A program to send and receive text to and from the
;24LC256 eeprom using software I2C routines.

;----- Configuration

#chip 16F88, 8 ;PIC16F88 running at 8 MHz
#config mclr=off ;reset handled internally
#config osc=int ;use internal clock
#include <I2CEeprom.h> ;Kent's header file

;----- Constants

#define sw PortA.0 ;toggle switch on pin 17
#define SerOutPort PortA.3 ;serial output on pin 2
#define SerInPort PortA.4 ;serial input on pin 3
#define SendAHigh Set SerOutPort on ;output logic levels
#define SendALow Set SerOutPort off
#define RecAHigh SerInPort on ;input logic levels
#define RecALow SerInPort off

#define SDA PortB.0 ;data on pin 6
#define SCL PortB.1 ;clock on pin 7
#define waittime 1 ms
#define chipwrite b'10100000' ;I2C address 000
#define chipread b'10100001'

#define eof 0xff ;end of file marker

;----- Variables

dim msb, lsb, datum as byte
dim address as word alias msb, lsb

;----- Program

dir PortA 0b11110111

InitSer 1, r2400, 1+WaitForStart, 8, 1, none, invert

if sw = 0 then ;read eeprom
address = 0 ;prime the loop
datum = eeprom_receive(msb, lsb)

do while datum <> eof               ;quit if end of file
  serSend 1, datum                  ;else send to terminal
  address ++                        ;set for the next byte
  datum = eeprom_receive(msb, lsb)
loop

else ;write to eeprom
serReceive 1, datum ;get first datum
address = 0

do while datum <> eof
  eeprom_send(msb, lsb, datum)
  wait 10 mS  
  address ++                        ;point to next address
  serReceive 1, datum               ;get next datum
loop

eeprom_send(msb, lsb, eof)          ;append eof marker

end if

---

Thanks, Thomas Henry

[Anobium]

Kent - This looks like the same issue that I am currently re. Does this circuit have pulls up on the I2C lines? If so, then the new code may resolve this issue. If not, ignore this comment.

[Anonymous]

Yes, I should have mentioned it. I do have 4.7k pull-ups on both lines.

Thomas Henry

[kent_twt4]

Thomas et al thanks for starting another thread, since we are talking about my old software I2C header file, as opposed to the GCBasic inbuilt routines. Things can get confusing in a hurry.

It's been quite awhile since I've played with the soft I2C. Also, couldn't find by Olimex Pic-P18 board, so the Pic-P40 and a 16f877A chip will have to do for my example. Even lost my soft I2C with pullup header file, good reason to share on the forum :).

Had trouble with the SerSend, so you get a double dose with a soft USART routine also, set for 9600 Buad. No internal osc with the 16f877A, so the OSC is 20MHZ crystal.

The original soft I2C header seems just fine. My trouble was with the SerSend, so here is my working example. No serial receive going on, just write some numbers, then read back every 30 sec on the terminal.

Let me know if any questions, I notice there was no include? in your posted code.

#chip 16f877A,20
#config OSC=HS

#include <I2CMstrSoftPullup.h> 'Or whatever you want to call it
#define SDA PortC.4            '16f877A
#define SCL PortC.3            '16f877A
#define waittime 1 ms
#define chipwrite b'10100000'  '24lc256 address 1010+A2A1A0+R/W
#define chipread b'10100001'
Dim address as Word

'InitSer 1, r2400, 1+WaitForStart, 8, 1, none, normal
'#define SerOutPort PortB.1 ;serial output on pin 2
'#define SerInPort PortB.0 ;serial input on pin 3
'#define SendAHigh Set SerOutPort on ;output logic levels
'#define SendALow Set SerOutPort off
'#define RecAHigh SerInPort on ;input logic levels
'#define RecALow SerInPort off
'dir SerInPort in
Call Ser_Init

address = 0
For logtemp = 0 to 255
    address = address + 1
    addrl = address
    addrh = address_h
    eeprom_send(addrh, addrl, logtemp)
    wait 10 ms   'Need some delay here for proper operation
    'SerSend 1, logtemp
    bin2ascii logtemp
    Xmit_RS232 10:Xmit_RS232 13  ;line feed, carriage return
Next
wait 30 s

Main:
Do
address = 0
For logtempA = 0 to 255
    address = address + 1
    addrl = address
    addrh = address_h
    eepromA = eeprom_receive(addrh,addrl)
    wait 10 ms
    'SerSend 1, eepromA
    bin2ascii eepromA
    Xmit_RS232 10:Xmit_RS232 13  ;line feed, carriage return

Next
wait 30 s
Loop
goto Main

Sub Ser_Init
;slight adjustment was required for 9600bps delay value
#define baud 103
#define halfbaud 52 ;place Read of SerRx in middle of bit
#define SerTxHigh Set PortB.1 On
#define SerTxLow Set PortB.1 Off
#define SerRx PortB.0
dir PortB.1 out ;Tx
dir PortB.0 in ;Rx
SerTxHigh ;Initial RS232 idle state
end sub

Sub RCV_RS232 
RxWait:
IF SerRx On Then goto RCV_RS232 ;wait for start bit
wait halfbaud us ;do half bit time delay
If SerRx On Then goto RxWait
RxByte = 0
For RxBit = 1 to 8 ;set up to read 8 bits
wait baud us
Rotate RxByte Right
If SerRx On then Set RxByte.7 1
If SerRx Off Then Set RxByte.7 0
Next
wait baud us
End sub

sub XMIT_PRINT (PrintData$)
PrintLen = PrintData(0)
if PrintLen = 0 then exit sub
'Write Data
for SysPrintTemp = 1 to PrintLen
XMIT_RS232(PrintData(SysPrintTemp))
next
end sub

Sub XMIT_RS232(Xmit_Byte)#NR
SerTxLow
wait baud us
For cntr = 1 to 8
Rotate Xmit_Byte Right
If Status.C ON Then SerTxHigh
If Status.C Off Then SerTxLow
wait baud us
Next
SerTxHigh
wait baud us
end sub

sub bin2ascii (LCDValue) #NR
LCDValueTemp = 0
LCDShowChar = 0
SERCEN = 0
SERDEC = 0
SERUN = 0

If LCDValue >= 100 then
LCDValueTemp = LCDValue / 100 
LCDValue = SysCalcTempX
SERCEN = LCDValueTemp + 48
Xmit_RS232 (SERCEN)
LCDShowChar = TRUE
End If

If LCDShowChar > 0 or LCDValue >= 10 then
LCDValueTemp = LCDValue / 10 
LCDValue = SysCalcTempX
SERDEC = LCDValueTemp + 48
Xmit_RS232 (SERDEC)
End If

SERUN = LCDValue + 48
Xmit_RS232 (SERUN)
End Sub

sub bin2ascii (LCDValue as word ) #NR
Dim SysCalcTempX As Word
LCDValueTemp = 0
LCDShowChar = 0
SERDECMIL = 0
SERMIL = 0
SERCEN = 0
SERDEC = 0
SERUN = 0

If LCDValue >= 10000 then
LCDValueTemp = LCDValue / 10000 [word]
LCDValue = SysCalcTempX
SERDECMIL = LCDValueTemp + 48
Xmit_RS232 (SERDECMIL)
LCDShowChar = TRUE
End If

If LCDShowChar > 0 or LCDValue >= 1000 then
LCDValueTemp = LCDValue / 1000 [word]
LCDValue = SysCalcTempX
SERMIL = LCDValueTemp + 48
Xmit_RS232 (SERMIL)
LCDShowChar = TRUE
End If

If LCDShowChar > 0 or LCDValue >= 100 then
LCDValueTemp = LCDValue / 100 [word]
LCDValue = SysCalcTempX
SERCEN = LCDValueTemp + 48
Xmit_RS232 (SERCEN)
LCDShowChar = TRUE
End If

If LCDShowChar > 0 or LCDValue >= 10 then
LCDValueTemp = LCDValue / 10 [word]
LCDValue = SysCalcTempX
SERDEC = LCDValueTemp + 48
Xmit_RS232 (SERDEC)
End If

SERUN = LCDValue + 48
Xmit_RS232 (SERUN)
End Sub

[Anonymous]

Thank you, Kent. I'll give it a whirl as soon as I can get my decrepit workbench laptop up and running (I hope yet tonight).

The Include is indeed in my file, but disappeared on the Forum posting. Just what is the secret of making code look right, including the comments, spaces and font?

Thanks again, so much for dipping into this.

Thomas Henry

[kent_twt4]

The Formatting Help button has the answer, been mentioned before, use the tilde's being sure their is a blank line before and after too.

"~~~~"
code here
"~~~~"

So without the exclamations:

code here

Check preview, and should be good to go now.

[Anonymous]

Hi Kent,

Well, you're right. The original header file code seems to be fine. I changed my experiment so that rather than getting the text to be written to the eeprom from the serial port, I get it from an internal string and send it one character at a time.

In a nutshell, either the software serial stuff is troublesome, or there's an unexpected interaction between your I2C eeprom code and the GC Basic software serial routines.

I'll have to rethink how I'm going to handle this, but at least I now know that it is possible to reliably read and write to the 24LC256 on its own.

Thanks again for your good work.

Thomas Henry