 Notice. New forum software under development. It's going to miss a few functions and look a bit ugly for a while, but I'm working on it full time now as the old forum was too unstable. Couple days, all good. If you notice any issues, please contact me. |
Forum Index : Microcontroller and PC projects : Problem with Terminal Emulator
| Author | Message | ||||
| subalib Newbie  Joined: 07/02/2019 Location: AustraliaPosts: 11 |
I am having a problem with my terminal emulator in that it will display text received from the Micromite but when attempting to send data to the Micromite nothing appears on the terminal screen nor is anything transmitted to the Micromite. I am using Tera Term and have also tried the MM Edit terminal emulator with the same result. The CP2102 appears to be working and if I bridge the Tx and Rx pins it echoes on the terminal screen and both LED's flash on the interface. When I plug the interface into the Micromite the Tx LED no longer flashes. I have also tried different USB cables to no avail. Given it worked well initially but has suddenly stopped working I am at a loss as to where to look next so any help would be appreciated. Thank you. David |
||||
Turbo46 Guru  Joined: 24/12/2017 Location: AustraliaPosts: 1642 |
I presume that you are using the console port and can see the startup message? Have you checked that the RX/TX connections between the Interface and the Micromite are correct? Checked them for continuity? Is your power supply adequate? Is the 47uF capacitor OK? Which Micromite are you using? Is it on a breadboard? If so add some capacitors across the supply? Bill Keep safe. Live long and prosper. |
||||
TassyJim Guru Joined: 07/08/2011 Location: AustraliaPosts: 6283 |
That looks like a shorted Tx line on the micromite. Jim VK7JH MMedit |
||||
| subalib Newbie Joined: 07/02/2019 Location: AustraliaPosts: 11 |
Thanks for the feedback. The device is a Micromite Explore 100 and is working well. The terminal emulator was working properly until recently when it ceased accepting commands from the PC even though commands to the Micromite via its keyboard are displayed on the PC. I have checked the Tx and Rx lines and they are making contact with the correct pins on the PIC chip and there are no short circuits. David |
||||
| Turbo46 Guru Joined: 24/12/2017 Location: AustraliaPosts: 1642 |
I suppose that if you had another CP2102 module to try that you would have mentioned it. If you are brave enough, you could power the Micromite down and short circuit the TX and RX pins on the Micromite chip and try the terminal emulator to see if you get the TX and RX LEDs on the CP2102 module both flashing. I just tried that with a 28 pin Micromite and it worked with no ill effects. That would eliminate all but the chip itself I think. Bill Keep safe. Live long and prosper. |
||||
| subalib Newbie Joined: 07/02/2019 Location: AustraliaPosts: 11 |
Thanks Bill. I have tried other CP2102 modules but unfortunately the problem seems to be on the board somewhere. David |
||||
| Turbo46 Guru Joined: 24/12/2017 Location: AustraliaPosts: 1642 |
Yes it does. I think that leaves the test I suggested above. You have checked the connections to the chip. Shorting the TX/RX pins on the CP2102 module pretty much eliminates the terminal emulator and besides you tried two programs. If you try that test and the RX and TX LEDs both flash then maybe re-flashing the chip may help? Bill PS You could try applying a little pressure to the TX and RX pins with an insulated probe while trying the terminal emulator in case you have a dicky connection between the chip pin and the PCB. Pressure applied while testing with a multi meter could mask that problem. Keep safe. Live long and prosper. |
||||
Grogster Admin Group  Joined: 31/12/2012 Location: New ZealandPosts: 9610 |
....then....it should be working.  Which version of the E100 PCB are you using? 1B? 1C? 1D? ...or the Silicon Chip version? EDIT: Do you happen to have a logic analyser such as a Saelie Logic thing? If you do, connect it the the micromite side of the serial adaptor, and start capturing on the logic software. Type something - anything. Stop capture, and examine the waveform on the logic software. This will at least tell you if you are getting pulses back towards the Micromite. At this stage, I am tending to agree with Jim - sounds like the RXD into the Micromite has a short to ground, as you have proved that your serial adaptors work via the loopback tests you have already done.(which was a good move, by the way - well done.) You say you have checked for continuity between the PIC32 pins and the console pins, but have you checked there is isolation between those pins and ground? I suspect you might find that your RXD(into the Micromite) may be connected to the PIC32 - and also ground via a short when it should not be. Testing between the PIC32 pin and the console pin might read as fine, but it might also be connected to ground aswell, and a simple continuity test end-to-end won't show that up. Put your multimeter on ground, and then touch the RXD line into the Micromite's console pin. If you get a reading - 'Houston, we have a problem....' Smoke makes things work. When the smoke gets out, it stops! |
||||
| erbp Senior Member  Joined: 03/05/2016 Location: AustraliaPosts: 195 |
In case you have a dry joint between the Console Rx pin and PCB (as suggested by Turbo46) try applying a hot soldering iron with just the smallest smear of solder to pin 89 (Console Rx pin). The "was working, suddenly not working" symptom is indicative of a dry joint problem. Phil. |
||||
| subalib Newbie Joined: 07/02/2019 Location: AustraliaPosts: 11 |
Thanks for all of suggestions. To answer the questions the board is a Silicon Chip PCB. I have tested between the Rx and Tx lines to ground and there are no short circuits. I have also resoldered the pins on the CPU to rule out a dry joint but still not working. I measured the open circuit voltage on the Rx and Tx pins from the CPU and they both show rail voltage of 3.3V. (Not sure what they should be!)Looking more like a fault in the processor chip. Perhaps its an excuse to build another one  David |
||||
| Turbo46 Guru Joined: 24/12/2017 Location: AustraliaPosts: 1642 |
I don't think that's right. On my 28 pinner the RX pin voltage is lower with or without the CP2102 module connected. Have you tried the USB console? Failing that I would re-flash the chip. If you don't have the equipment for that then it's a good excuse to build the Microbridge. Bill Keep safe. Live long and prosper. |
||||
| subalib Newbie Joined: 07/02/2019 Location: AustraliaPosts: 11 |
Thanks Bill. I haven't tried the USB console as I need to purchase a cable. I am also awaiting delivery of the Microbridge kit so will do a re-flash once I have built that. David |
||||
| Turbo46 Guru Joined: 24/12/2017 Location: AustraliaPosts: 1642 |
Great! Please let us know how you go. I can recommend Robert Rozee's PIC32PROG ascii ICSP graphical user interface for driving the Microbridge. I can be found in the Document Register. Bill Keep safe. Live long and prosper. |
||||
| erbp Senior Member Joined: 03/05/2016 Location: AustraliaPosts: 195 |
Here is one more thing you can do without needing a Microbridge to reflash the chip. I checked this on my E100 just now. With the E100 powered up but nothing connected to the console pins, the TX pin (87) measured 3.25v (this with the 3.3 measuring 3.26v - maybe my multimeter is slightly off). The RX pin (89) only measured 2.18v - so definitely lower. I believe the RX pin has a weak pull-up to 3.3v enabled in the PIC32 chip, so would expect something like this. Now the important thing is to determine whether the pull-up is indeed weak, thus allowing the USB to Serial chip to be able to pull it down to ground or whether it has a short to 3.3v which would not allow the interface to pull the signal low. So, connect a 1K resistor in series with your multimeter, set the meter to read milliAmps and connect the meter/resistor between the RX pin and ground. On my E100, I measured a current of 260uA. If you have a short (or very low resistance pull-up on the RX line) you would see a current around 3mA. If this is the case, you either have a shorted track (to 3.3v not ground) or there is some damage to the PIC32 chip. Hope this helps. Phil. |
||||
| subalib Newbie Joined: 07/02/2019 Location: AustraliaPosts: 11 |
Thanks Phil I did your little test and measured around 2.85mA on both the Rx and Tx so based on this there seems to be a problem with the chip or PCB. When I have the programmer available I will reprogram the chip as I have nothing else to lose. David |
||||
| erbp Senior Member Joined: 03/05/2016 Location: AustraliaPosts: 195 |
Always worth re-flashing the firmware when odd behaviour happens. There are quite a few instances recorded on this forum where that has solved mysterious situations. Best of luck. Phil. |
||||
| Turbo46 Guru Joined: 24/12/2017 Location: AustraliaPosts: 1642 |
You will need a mini USB cable for the Microbridge. Bill Keep safe. Live long and prosper. |
||||
CaptainBoing Guru Joined: 07/09/2016 Location: United KingdomPosts: 2170 |
+1 A lesson I learned early on... nearly drove Geoff potty with a MM2 that wouldn't count backwards with a STEP -1... guess what fixed it  It is my go-to now when I get weird stuff happening. I must say 99% of the time it is my code but I have had a few times where crazy stuff was happening and a re-flash fixed it. It only seems to happen when I am developing (and since I started using a different method for entering the prog, I don't think it has happened at all) - once the code is at a releasable level and burned into a "production " MM I have never had this problem, so I suspect is it something to do with Flash timing internally or sorcery. |
||||
 Print this page |
 |
The Back Shed's forum code is written, and hosted, in Australia. | © JAQ Software 2025 |
