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How to read back registers on ADV7511

Question asked by psusi on Jul 20, 2017
Latest reply on Jul 21, 2017 by psusi

I started with writing the fixed registers identified in the programming guide:


    static const uint8_t registers[][2] = { { 0x98u, 0x03u },
                                            { 0x9au, 0x70u },
                                            { 0x9cu, 0x30u },
                                            { 0x9du, 0x01u },
                                            { 0xa2u, 0xa4u },
                                            { 0xa3u, 0xa4u },
                                            { 0xe0u, 0xd0u },
                                            { 0xf9u, 0x00u },


Each one is written in its own I2C transaction consisting of start, address in write mode, write register address, write register value, stop.  Each sent byte is ACKed by the ADV7511.  I then tried to read them back to verify they had been accepted in transactions consisting of start, address with write bit set, register address, restart, address with read bit, read byte, stop.  The ADV7511 always responds with all zeros ( holding SDA low ).  Why won't it return the values written to the registers?