Quote:
Originally posted by Rickertsen2
Hmm... Not only is there "PWM IN" but the "PWM outs" are 4 pin instead of 3pin. I wonder if they will not be using standard RC type interfaces for the speed controllers. Maybie you connect the plug between one set of pins for 2ms out and one way for 17ms out. This may or may not be possible depending on the pinout, but right now im too lazy to look it up.
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The PWM output on the EduRC have historically been 4 pin connectors. On last year's EduRC, two of the four pins were connected to Vcc. The motors used one supply for logic, and the other for powering the motor itself. I doubt this has changed. I'm willing to bet that there are a few specific PWM outputs which will be 2ms, and specific outputs which will be 17ms (say outputs 1-4 are 17ms, and 5-8 are 2ms, for instance).
Quote:
Originally posted by Jnadke
Here's my take. I think there are 2 PICs in the RC, and the master serial ports are interconnected. As before, the data is shared between them. One handles the I/O and the other processes the user code. One of the USART ports on the I/O chip is probabaly used for an A-to-D converter. The microcontroller does have an internal A-to-D converter, but I think they would use that for the Digital In/Out, since it supports both. The relays are probabaly controlled by the I/O ports. The last USART is probabaly used for the communications radio.
On the programming chip side of things, I don't think any inputs would be used, other than the interrupts. Even then, they only enable 6 interrupts out of the 13 available (probabaly used for the microcontroller signalling). As before, the master serial port is probabaly used for intercommunication. The two USART's are probabaly used for the programming port and the TTL serial port for the custom circuit.
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Being as the 18F8520 has an onboard 16 channel, 10bit ADC, I would expect those inputs to go directly to the user programmable microcontroller on the EduRC, rather than having another arbitrary layer separating us from the data. On the FRC RC, however, this may not be the case, being as they have the inputs listed as 16 analog
and 16 digital (in or out). I guess we'll have to wait a little longer for clarification on this.
Regarding interrupts, however, while I might be able to explain some, I am confused about something. You're correct in that there are 13
sources for interrupts, at two different user-selectable priority settings, on the controller, but there're only 4 external hardware interrupts available on the 18F8520, with the rest being software related (timer interrupts, USART Tx empty and Rx full interrupts, A->D conversion complete, etc.). INT[0-3] are pins 55-58 (in reverse order), so I am very curious as to how they're getting 6 external hardware interrupts.
I guess this all means that, despite IFI releasing so much information to the public, the answers they've given have only produced more and more questions.
Time will tell.
Wow... no duct tape? - Stormnnormn [more] 
03-10-2003, 18:29
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