STM8S I2c

debruyne.marc · ‎2013-01-30

Posted on January 30, 2013 at 11:34

hello,

i try to make a connection between the stm8s207 and an pcf8574.

the problem is with the software, because i can control the pcf8574 with an AARDVARK analyzer.

when i send a start and an adress (40) for pcf8574 then i do not see any pilses on PE1 and PE2

i use a crystal of 14.7456Mhz because of the UART.

please take a look at the attached assembly file.

and ,let me know what i doing wrong.

many thanks

marc debruyne

Stm32User · ‎2013-02-08

Posted on February 08, 2013 at 13:52

Is there any particular reason why you are writing in assembler ?

Why not write in C ? You can then use the ST firmware library which has I2C drivers already written and debugged.

klaasdc · ‎2013-02-08

Posted on February 08, 2013 at 15:45

I once had problems with I2C on the 105c6 because these pins have no internal pull up function. Maybe you have the same problem?

There was more here:

https://my.st.com/public/STe2ecommunities/mcu/Lists/STM8SDiscovery/Flat.aspx?RootFolder=%2Fpublic%2FSTe2ecommunities%2Fmcu%2FLists%2FSTM8SDiscovery%2FGPIO%20Pull-up%20resistors%20on%20Port%20E&FolderCTID=0x01200200770978C69A1141439FE559EB459D758000CCDF802E596CAF44ADED5E61F5CA8B1B&currentviews=562

Andrew Neil · ‎2013-02-10

Posted on February 10, 2013 at 16:11

''these pins have no internal pull up function. Maybe you have the same problem?''

That could explain why it works with the Aardvark - perhaps the Aardvark provides pullups...?

A complex system that works is invariably found to have evolved from a simple system that worked.
A complex system designed from scratch never works and cannot be patched up to make it work.

debruyne.marc · ‎2013-02-11

Posted on February 11, 2013 at 11:18

hello sir,

no the aardvark use the 7 bit and must be set to 20 while the normal addres for a 8574 is 40

the aardvark people told me that;

and its working