Post by thread:[EE]: RS232 activity LED's

any good ways to monitor comm status? I have a UART driving a MAX232, and I want to monitor the tx/rx lines with an LED. Tried just to attach a transitor driver to an LED but it seemed to load it down too much and the comm has errors. Next is to use a TTL gate, but wondered if anyone had a quick solution they have used before? _________________________________________________________________ Get your FREE download of MSN Explorer at http://explorer.msn.com/intl.asp -- http://www.piclist.com hint: To leave the PICList spam_OUTpiclist-unsubscribe-requestTakeThisOuTmitvma.mit.edu

> any good ways to monitor comm status? I have a UART driving a MAX232, > and I want to monitor the tx/rx lines with an LED. Tried just to > attach a transitor driver to an LED but it seemed to load it down too > much and the comm has errors. Next is to use a TTL gate, but wondered > if anyone had a quick solution they have used before? I have used a series diode, 2k2 resistor and LED to ground on both Rx and Tx. This does load down the signal by a volt or two but that is not enough to adversely affect comms. (This was with an Analog Devices ADM202 chip). A transistor driver should be OK, but it sounds like you tried it with little or no base resistor. Try 22 - 47k and you should get better results. Brent Brown Electronic Design Solutions 16 English Street Hamilton, New Zealand Ph/fax: +64 7 849 0069 Mobile/text: 025 334 069 eMail: .....brent.brownKILLspam@spam@clear.net.nz -- http://www.piclist.com hint: To leave the PICList piclist-unsubscribe-requestKILLspammitvma.mit.edu

2N7000 or other suitable VFET driving LED in open drain config. Some BF245 (A or B I think, selected) can drive a LED w/o a limiter resistor in source follower config. The Rdson is just right for a LED at 5V (don't try this with 2N7000 or other VFETs - BF245 is an ancient JFET). Peter -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads