MultiSerial Shield

MultiSerial Shield

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Function:	Provide two RS232 ports with 3.3v or RS232 levels, accessible via I2C.
Key Chips:	NXP SC16IS752
External Ports:	2x RS232 (3.3v or RS232 levels), 10x GPIO
Required Pins:	A4 (I2C SDA), A5 (I2C SCL)
Optional Pins:	None

Project Status

PCB design complete, prototype PCBs ordered and received from BatchPCB. Full BOM entered at Digikey (SC16IS762 substituted instead of SC16IS752 because the latter is out of stock for another 6 weeks and the former is pin-compatible), but still need to place actual order.

Revision 1 PCB Issues

• Should connect GND pins on Arduino header together
• +5V and GND labels on RS232 port are swapped
• Pins 15-28 on controller IC are mirrored! Doh!

Overview

The Arduino MultiSerial shield will let the Arduino access two RS232 serial ports via I2C. It will have switchable 3.3v or RS232 levels. This project exists mainly as a debugging tool for networks of BlinkieBits, as (at least during BlinkieNet design/prototyping) it would be extremely useful to be able to receive debugging information from a whole network of BlinkieBits, rather than just one at a time.

• The NXP SC16IS752 chip is used, which gives 2 channels for ~$7. It needs 3.3v I/O and talks 3.3v RS232, so level shifters are needed. The I2C level shifter is a PCA9306 ($0.95 qty. 1), and the RS232 level shifter is a second-sourced TI MAX3232 in a SOT16 package ($1.70 qty. 1).

MultiSerial Shield Rev. 1 Schematic