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MicroSquirt Serial RX/TX voltages
Posted: Tue Oct 12, 2010 9:40 am
by 24c
Does anybody know what voltages are seen on the RX TX pins? I'd try and measure them, but I am working away this week, and I'd like to order an adapter. I looked at the spec on the MAX3221 and am now even more confused than normal.
Re: MicroSquirt Serial RX/TX voltages
Posted: Wed Oct 13, 2010 8:34 am
by Matt Cramer
They're RS-232 level, that is, 12 volts.
Re: MicroSquirt Serial RX/TX voltages
Posted: Thu Oct 14, 2010 12:46 am
by 24c
Thanks for that
Matt, I knew RS232 was 12V, but was unsure what the MicroSquirt was chucking out, so I now need an RS232 level converter/shifter to reduce it to 3.3V
I am still working away, but at least I can hit the online shopping button, and hopefully the parcel will be there when I get back home.
Re: MicroSquirt Serial RX/TX voltages
Posted: Thu Oct 14, 2010 5:07 am
by Matt Cramer
Wait, were you asking about the voltages coming INTO the serial chip? I don't believe they are accessible from any jumper pads and I thought you meant the pads at the 4 pin header.
Re: MicroSquirt Serial RX/TX voltages
Posted: Thu Oct 14, 2010 5:32 am
by 24c
Matt, I meant from the jack plug breakout out of the AMPseal connector on the MicroSquirt, which is pin 13, 14 & 19, and also the equivalent for the Module board, which are pin 4, 6 & 31.
EDIT> I have just read the USB add on notes from the Module info pages and it covers all my questions....
But, since USB is higher speed compared to UARTs (a.k.a. serial port) noise in an automotive environment can be an issue. Additionally, the signalling from the Microsquirt module is RS-232 signal levels (+/- 12 volts), not TTL level, so level translation is required.
PS Ordered one of these...
http://www.sparkfun.com/commerce/produc ... cts_id=718
Thanks for your help.