I am trying to become a freak, desperately, but I just can't seem to cut it :) My current challenge is to write a small program (preferrably in C, not assembly) which enables an ATMEL micro to "talk" to my Casio 9750 calculator :oops: yes I freeks too :oops: :lol:
Alberto Ricci Bitti has "cracked" the Casio communications protocol, showing how to mimic the handshaking and sweet-talking the Casio expects when doing Send() and Receive(), one variable at a time: See Ricci's site; in particular his dissection of the Casio protocol!
This circuit can be used in several ways; as an external datalogger (as suggested by Bitti); as the brains of a Casio <-> Casio cable (for "chat programs", or two-player gaming)... And -- most importantly -- as an excellent way for me to learn basic (?) AVR programming :)
At this point I need help :-D
I have set up my spanking new STK500 and got Dean's USART C program working fine within an ATMEGA16, so I'm quite happy! Would someone please help me get a bit further? Questions:
- I assume the Casio uses TTL voltage. How can I test/verify this? And, if so, does this mean I need to include an RS232 (MAX232) chip in the design?
- For debugging/testing, can I connect the Casio directly to some pins on the STK? What about the RX/TX (PD0/PD1) pins of "PORTD"? How can I be sure not to fry the Casio (or the STK)? The Casio uses a standard stereo "minijack" plug for serial comm,
- How do I have the micro execute the "casio protocol" in the correct order while receiving the Send() operation?
So thankful for any and all help!