Problem communicating with SC16IS752 Dual UART chip

Hi folks,

I am trying to use the SC16IS752 Dual UART with I2C-bus/SPI interface chip with a BSOM. I've wired the board up as seen below using a 1.8432 MHz external oscillator. I want to communicate with the chip using I2C (with 5.7K pull-up resistors on SCL and SDA) and am using address 0x48 using pins 10 and 11. However, when I use the I2C scanner, it doesn't turn up any devices. I've also been referencing rickkas7's library for SC16IS7xxRK and intend on using it for further development.

Does anyone have experience with this chip for dual UART over I2C? Or anyone see anything that is incorrect in the wiring diagram? Thanks!

I read through the UART data sheet and it looks like you are hooking up correctly.

Do you have pull-ups on SCL and SDA?

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Are you using a bare chip or a breakout board? The SDA and SCL each need a pull-up to 3V3, typically 2.2K to 10K. Most breakouts have a 10K, but if you're using a bare chip you need to add external pull-ups.

You have pin 9 (I2C/SPI) pulled high, so it should be in I2C mode. You have pin 10 and 11 (A0 and A1) tied to 3V3 so the address should be set.


There are 5.7k pull-ups on SDA and SCL (I edited the original post to make that clear!). I am using the chip soldered on a TSOP28 breakout board.

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Given that the I2C scanner can't find the chip, there's something wrong, but it's not clear what. Is /RESET (pin 5) pulled high?

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It was the reset pin! Thanks for your insights. :slightly_smiling_face:

I am now successfully communicating with a wind sensor over RS232 on channel A. It publishes data at a rate of 1hz. I am trying to communicate with a battery charge controller on channel B. It uses RS-485 ModBus RTU half-duplex communication. I want to be able to read the charge state from a particular register of the charge controller. When I communicated with the charge controller previously, I used the ModbusMaster library.

I am a bit perplexed about how to read from a register on the charge controller. Has anyone communicated with a similar device/have some starter code or tips that could get me pointed in the right direction?

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