Q: When I add a CAN or RS485 driver chip to the CGCOLORMAX2 do I have to connect the driver to the microcontroller I/O lines?
A: For the CGCOLORMAX1 and RS485 the logic level lines needed to be connected, as the RS485 circuit was floating separately from the rest of the design.
For the CGCOLORMAX2 the CAN and RS485 logic level lines are connected to the appropriate lines of the microcontroller. Without the driver chips in place, the circuits are effectively not there. Once the chips (through-hole DIP packages) are installed, the circuits become a part of the CGCOLORMAX2.
Q: When I add the CAN driver chip to the CGCOLORMAX2, do I lose some I/O lines? And what CAN driver is recommended?
A: Yes. The data lines for the CAN driver chip connect to pins D4 and D5 on the shield connector. To avoid interference any shield used should not have a connection to D4 and D5.
One recommended CAN driver chip is the Microchip MCP2551.
Q: When I add the RS485 driver chip to the CGCOLORMAX2, do I lose some I/O lines? And what RS485 driver is recommended?
A: RS485 capability makes use of MMBasic serial port 1 TX, RX, and RTS lines. Adding the RS485 driver chip uses these lines and renders them unusable as general I/O lines. These lines are MMBasic I/O pins 15-17.
There are quite a few RS485 driver chips that have the same pin out. The TI SN75176 is one such appropriate chip.
Q: How does the RS232 driver chip support one or two serial ports?
A: MMBasic serial port 1 can be TX/RX, or it can be TX/RX/RTS/CTS. When the RS232 driver chip is used for all four signal lines of MMBasic serial port 1, then the driver chip can support level conversion for TX/RX/RTS/CTS.
As an alternate, two RS232 serial channels can be supported by the driver chip. MMBasic serial port 1 would use just TX/RX for communication (not the RTS/CTS lines of MMBasic serial port 1) and MMBasic serial port 2 TX/RX lines would connect to the RS232 chips other driver/receiver pair that are labeled RTS (for MMBasic serial port 2 TX) and CTS (for MMBasic serial port 2 RX).
The MAX232 driver chip is just two RS232 transmit/drivers and two receivers. You can exchange them as needed.
Q: What driver chip should be used as an RS232 driver?
A: The Maxim MAX232.
Q: When I insert the RS232 chip, am I automatically connected to the microcontroller like the RS485 chip does?
A: No. For the CGCOLORMAX1 and CGCOLORMAX2 you have to hook up the logic level (MMBasic port lines) to the chips. This is set up so that you have the greatest flexibility in using the RS232 driver chip.
Q: Does the shield reset line reset the MMBasic microcontroller?
A: Yes. That reset line is active low, by the way.