Write to and later read from EEPROM

Spoppe · 2013-04-27 09:50

Building a data logger. One program measures data and writes it to EEPROM. Another program later reads the data from the EEPROM. Using Word vars. but the program that reads always gets zeroes for the high byte. Low byte is ok. What is going on? How can i read the data correctly? I have confirmed that the writing program can immediately read the data correctly. This is on BS2.

Mike Green · 2013-04-27 10:01

Can't tell what's going on for you without source code. Please post. The examples shown in the manual (see READ / WRITE) do work.

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Remember that you need the WORD prefix to read and write words like: WRITE <address>, WORD <data>
Remember also that, if you're using WORD, that the addresses should increment by two.

Spoppe · 2013-04-28 09:17

The symptom has changed. Now I cannot get the same data back immediately after writing it. Below I post the full code and then some sample output.

' PulseIntervalTimer2.bs2
' Measure the intervals between successive HIGH states on an input pin
' Pin 14 is the input pin
' An on-board astable multivibrator generates a pulse train
' which is fed to pin 14
' This method uses the pulsin command
' {$STAMP BS2}
' {$PBASIC 2.5}
locount VAR Word   'count of 2 usec intervals for low pulse
hicount VAR Word   'count of 2 usec intervals for high pulse
cyclecount VAR Word      ' count of 2 usec intervals for a cycle
memloc VAR Word     'memory location
memlochi VAR Word  'highest memory location to use
memcontent VAR Word ' content read from a memory location
memloc = 0
memlochi = 10
DO UNTIL memloc = memlochi+1
  PULSIN 14, 0, locount          ' count duration of low state
  PULSIN 14, 1, hicount          ' count duration of high state
  cyclecount = locount + hicount ' compute count for one cycle
  DEBUG ? cyclecount             ' echo cycle count to screen
  WRITE memloc, Word cyclecount  ' write cycle count to eeprom
  READ memloc, Word memcontent   ' then immediately read it and echo to screen
  DEBUG "memory location  ", DEC memloc, "  memory contents  ", DEC memcontent, CR
  memloc = memloc + 1
  LOOP
'  Check what is read from memory to see if it is as expected
memloc = 0
DO  UNTIL memloc = memlochi + 1
  READ memloc, Word memcontent
  DEBUG "memory location  ", DEC memloc, "  memory contents  ", DEC memcontent, CR
  memloc = memloc + 1
  LOOP
END

Here is some output:

cyclecount = 10283
memory location 0 memory contents 10283
cyclecount = 10282
memory location 1 memory contents 10282
cyclecount = 10283
memory location 2 memory contents 10283
cyclecount = 10282
memory location 3 memory contents 10282
cyclecount = 10280
memory location 4 memory contents 10280
cyclecount = 10283
memory location 5 memory contents 10283
cyclecount = 10281
memory location 6 memory contents 10281
cyclecount = 10282
memory location 7 memory contents 10282
cyclecount = 10283
memory location 8 memory contents 10283
cyclecount = 10283
memory location 9 memory contents 10283
cyclecount = 10283
memory location 10 memory contents 10283
memory location 0 memory contents 10795
memory location 1 memory contents 11050
memory location 2 memory contents 10795
memory location 3 memory contents 10282
memory location 4 memory contents 11048
memory location 5 memory contents 10539
memory location 6 memory contents 10793
memory location 7 memory contents 11050
memory location 8 memory contents 11051
memory location 9 memory contents 11051
memory location 10 memory contents 10283

Steve

PJAllen · 2013-04-28 09:32

You can't write a WORD, 16 bits, to one 8-bit register.
You have to divide that WORD into two BYTEs and WRITE them into two registers.
Same goes with READ.

Mike Green · 2013-04-28 09:33

When you write (or read) a word value, that takes two bytes. You have to increment the memory location by 2

READ memloc, word memcontent
WRITE memloc, word memcontent

You have to do

memloc = memloc + 2

Spoppe · 2013-05-02 20:45

Thank you, Mike. That works perfectly.

Write to and later read from EEPROM

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