[fpc-pascal] FPC/Lazarus on RPi4 - How to read/write I2C connected EEPROM?

[Bo Berglund]

On Sun, 02 Apr 2023 15:07:48 -0400, Dennis Lee Bieber via fpc-pascal
<fpc-pascal at lists.freepascal.org> wrote:

>On Sun, 02 Apr 2023 16:16:46 +0200, Bo Berglund via fpc-pascal
><fpc-pascal at lists.freepascal.org> declaimed
>the following:
>
>
>>
>>----------------------------------------------------------------
>>Byte Write
><SNIP>
>>a  location  within  a  64  byte  page.  A  byte  following  the
>>address bytes will be interpreted as data. The data will be
>>loaded into the Page Write Buffer and will eventually be
>>written to memory at the address specified by the 14 active
><SNIP>
>>The Master then starts the internal Write cycle by issuing a
>>STOP condition (Figure 6). During the internal Write cycle
>>(tWR), the SDA output will be tri-stated and additional Read
>>or Write requests will be ignored (Figure 7).
>>------------------------------------------------------------------
>>
>	This sounds suspiciously like one is expected (or is able) to write
>multiple bytes /within/ the "page" via multiple address/data operations,
>and have all those bytes "burned" into the memory using a single "stop"
>operation.
>

Exactly, you specify *start* as a 2-byte address (pageno/offset) and then you
output as many sequential bytes as you need to write in the command.

All will wind up in the 256 byte on-chip write buffer until the stop arrives and
then it will be dumped into memory. If the buffer address increments past 0xff
it will wrap back into 0x0 in the buffer for following bytes and this is
probably something you must not allow...

So an application using i2c must check the arguments for this page transition
case and either error out or spawn a second operation for the following page in
EEPROM to handle the excess bytes.

I have not yet tested this case because the github project does not have an
i2c_write demo...
Must write one myself.


-- 
Bo Berglund
Developer in Sweden