Wonderful !! The program apparently shifts the address bits (rlf) once before transmitting, i.e. converts to a 7-bit address. That was a tad confusing to me, the neophyte, but I accepted their description. I presumed that the 7-bit address was somehow different from the normal 8-bit decoding ...

Thanks for the idea ... alas, 'tis NoGo. Adding a jumper to pins5/6 on the keypad interface = no change. Attached is a screen capture of the SCL and SDA lines (the attachment is a zipped PDF). Anything pop out? I also reversed the SCL and SDA connections, just in case the pinouts were incorrect. As ...

Rev1.5 (c)2003
Matrix Orbital LK202-25-E (handwritten E)

The slave address transmitted = 0x50 (with the msb 0 suppressed for a 7 bit address). This has been verified by monitoring the I2C SCL/SDA lines with a scope. At the end (the 9th SCL), the SDA line stays high = no ACK from the display.

Jumpers? Have read the user manual several times, and done a ...

The situation consists of an LK202-25 display and a PIC 16F876 executing the PIC application note 725 programs (modified with slave address 0x50). I can monitor the SCL/SDA lines and see the correct slave address bits are transmitted. The LK202 does not respond with an ACK. Both the SCL and SDA have ...