I in the planning/information gather stage.

I want to replace the guts of a robo dog with a raspberry pi 3. It seems to have 8 serial interfaces with 8 pins(not necessary all in use).

I am trying to figure out the minimal amount of additional circuitry necessary to communicate with each of the 8 parts.

My first though was to divvy the 20 GPIO pins. What is the fastest speed I could achieve? How bad would this be for CPU utilization?

  • It seems to have 8 serial interfaces ...that does not make complete sense ..... which robo dog is it?
    – jsotola
    May 15, 2018 at 1:50
  • @jsotola The Sony Aibo (210 I think). Each leg,arm, head, and etc have individual control ports.
    – cybernard
    May 15, 2018 at 3:52
  • I'm pretty sure these aren't RS232 control ports, but I²C or SPI.
    – Janka
    May 15, 2018 at 13:27
  • he said serial, not RS232...... I2C and SPI are both serial as well.
    – Chad G
    May 15, 2018 at 16:37

1 Answer 1


Rpi has only one serial UART channel. So for 8 channels, you need to use software to config GPIO pins as UART. However, software UART on rpi/linux is not that reliable, even at low speed (9600baud).

Or you can use 8 SC16IS750 modules for hobbyists (less than US$10 from eBay).

SC16IC750 I2C UART module

SC16IS750 is a slave I2C-bus/SPI interface to a single-channel UART.

  • offers data rates up to 5 Mbit/s and low operating and sleeping current.

  • enables protocol conversion from I2C-bus or SPI to and RS-232 and are fully bidirectional.

SC16IS750 Datasheet


  • Does one chip give me 8 ports or 1? Do I need to make room for 8 of these chips?
    – cybernard
    May 15, 2018 at 11:39
  • Only one UART channel on one board. So you need 8 boards for 8 UART channels. Each board is about 2.5cm x 3cm.
    – tlfong01
    May 15, 2018 at 12:55

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