PHCC Communication Interfaces, Busses, and Protocols
The following communication protocols are used in the PHCC system:
- RS-232 (between PHCC motherboard and the host PC).
- Digital Output Type A bus (using the AP2PP protocol).
- Digital Output Type B bus (using a two-wire syncronous serial interface).
- I2C bus.
The PHCC system and the host PC have their own protocol stacked on top of the RS-232 bus. Details of this protocol can be found in the following documents:
- Host to PHCC: Media:Host2PHCC_Protocol.xfig.pdf
- PHCC to Host: Media:PHCC2HostProtocol.xfig.pdf
- The analog all axes dump differ from specification in firmware 0.1.8. The first packet sent by the motherboard only contain the packet type (b10100000). The next packet contains the upper 2 bits from the 10 bits ADC. The following byte contains the rest of the 8 bits from the ADC. These two packet are repeated for each analog input. The all-bits-one-byte and "all-bits-zero-byte" finally close the transmission. For more information, consult line 899 from Media:Firmware18.asm.