Questions about serial / UART on Javelin, i need to know ASAP! Also can you ho
WuLabs
Posts: 7
Hi
Before I buy, I need to know 3 things:
1)
How many serial ports can the Javelin have running at one time? This is not clear in the manual (i read the whole thing), on the Parallax website it can handle 7 UART's at a time, but this is not supported anywhere in the manual. I read on another website that the Javelin can run 6 single direction UART's (i.e. 6 single direction serial comm) or 3 FULL Duplex in the background. Is this true?
I need a micrcontroller that can handle at least 3 full duplex, or 2 full duplex and 2 unidirection simultaneously.
2)
I want to use an RC transmitter to control my robot, is it possible to have input pins take in a PWM in the background? I read the manual and it doesn't seem like you can. Or, I was just thinking maybe you can use an input as A/D, which would be a rough way to measure the 0-255 RC receiver input.
3)
FOr the serial ports, will they work on any specified pin? ANd the non COM ports on the board, they are in TTL right? So i will need to buy a TTL to RS232 converter like this one http://www.superdroidrobots.com/rs232.htm. Will this work?
Help please i need to purchase this very sooooon.
Before I buy, I need to know 3 things:
1)
How many serial ports can the Javelin have running at one time? This is not clear in the manual (i read the whole thing), on the Parallax website it can handle 7 UART's at a time, but this is not supported anywhere in the manual. I read on another website that the Javelin can run 6 single direction UART's (i.e. 6 single direction serial comm) or 3 FULL Duplex in the background. Is this true?
I need a micrcontroller that can handle at least 3 full duplex, or 2 full duplex and 2 unidirection simultaneously.
2)
I want to use an RC transmitter to control my robot, is it possible to have input pins take in a PWM in the background? I read the manual and it doesn't seem like you can. Or, I was just thinking maybe you can use an input as A/D, which would be a rough way to measure the 0-255 RC receiver input.
3)
FOr the serial ports, will they work on any specified pin? ANd the non COM ports on the board, they are in TTL right? So i will need to buy a TTL to RS232 converter like this one http://www.superdroidrobots.com/rs232.htm. Will this work?
Help please i need to purchase this very sooooon.
Comments
The Serial, PWM and probably a few other bits are classed as Vertual Perphiferal (VP) which mean the Javalin jumps off and processes them in the back-ground. I.e. to fill a serial recieve buffer with in-comming traffic etc. The Javalin is limited to 6 VP's at the same time. Each Uart is single directional - so yes you are correct with (1)
(2) PWM is a VPN as well - so you cannot run 6 VP's and PWM at the same time. Best bet to offload the PWM generation to another processor.
(3) - yes - P0 to P15. Yes you will need an RS232 line driver to invert the signal levels and bump to 12V
Hope this helps
James
First, the javelin can run 6 VP simultaneous, but I advice to use one VP
for timers. You can have as much timers as you want, that would still
be just one VP. That leaves five VP's for uarts, pwm generating, DAC and ADC.
For the uarts, use one VP to serve the transmit uarts. Normally the timing
on responses is not critical and a few msec to install a VP to respond
makes no difference. So, with a timer VP, you can still have 4 bidirectional
uarts, just by stopping and starting the correct transmit uart. Without
timers you could make that five. For hardware handshake uarts you
could even increase that number, if you put the handshake pin in notready
state and then stop the uart, releasing the VP slot for another handshake
controlled uart. The true limit is the number of pins. With 16 pins
you can have 5 bidirectional uarts without handshake (10 pins) +
6 transmit uarts without handshake or
3 receive/transmit uarts with handshake or
combination.
regards peter