Messing about with a HOLTEK HT9290A chip.

• https://hackaday.io/project/171885-control-a-obsolete-holtek-ht9290ab-dtmf-dialer

• control reading and writing from a µcontroller pin / button
• improve reading

• reading

• after sending a read command, the HT9290 sometimes starts sending data back before the microcontroller has finished sending the read command.

• it appears that when this happens, the following 5 bit chunk is identical to the unreadable one

• writing

• maybe it only takes the first number written after powering up

• could be that it is stuck waiting for more data to be written

• sensitive to number of bytes written after?

• triggering "dialing"

• dailing stops on a read command. perhaps on other commands