I have an arduino uno R3 on hand; any issues with using that instead of an arduino nano? The processors are the same, I believe the code is the same, and we only need two output pins so we should be good? I'm just brand new to arduinos.
I have an arduino uno R3 on hand; any issues with using that instead of an arduino nano? The processors are the same, I believe the code is the same, and we only need two output pins so we should be good? I'm just brand new to arduinos.
Great write up on the hardware side.
Can you give some insight how the software side of actual communication will work. Does it use comm port, is it transparent or some translation between cable and pcm is done, checksum and so on. The usual stuff we need to get a good start with it.
I've yet to delve into this for lack of time, but I believe any 328P based arduino / clone will work. It looks like I'll need some zeners to test but I intend to try with a bare breadboard clone and a FTDI cable.Originally Posted by sherlock9c1
Edit: one advantage to using a clone that lacks an integral usb>rs232 adapter is that the RTS line can be disconnected, eliminating the microcontroller reset caused when the serial port is opened by the client application.
Last edited by spfautsch; 01-29-2022 at 07:11 PM.
No zener? I just used a 9V battery in place of the zener supply for a while. The circuit is quite forgiving...
-Tom
I hadn't even looked at the schematic other than to identify you were using a transistor pair to drive the output, etc. It's hard to read, is that rail voltage 6.2 or 8.2 volts? I should have a 7806 and maybe even a 7808 3 pin regulator in my parts bin.
Regardless, if this bus is electrically similar to the older 8192 baud ALDL, I have to wonder (and will experiment with) a simple resistor and diode arrangement as I used on my data logger.
The objective is to send 6.25 - 8V when the output is active and high impedance when it is passive. The rest of the symbol info is in the timing of transitions. Any 8V regulator will allow for the drop in your output stage and should work a treat and you won't need a zener diode to regulate. You could avoid transistors and so on by using a 1488 rs2323 driver and a resistor. While you might not be in spec with the J1850 (rise time/fall time issues) it will work fine. When I did the circuit, I just went to my parts drawer and used what I have. Looking at it with the scope I see no problems.
-Tom
Thanks for the clarification.
Out of curiosity, did you test with TTL levels? I know it wouldn't be within spec but the 328P will happily sink 20ma per pin at 5V with no issues driving the outputs active high. When not driving the pin it could be toggled to an input / high impedance state.
I did try 5V, didn't work for me. Interested if you test.
Didn't understand the 2nd bit... No need to sink any current. Passive state is high Z. Active state sources current. Issue I had is that 5V doesn't seem to be enough to toggle the input stage. If you can get it to work, all the resistors & transistors involved with the TX can be removed with just a small bit of software change. I power the NANO through USB. There are some voltage losses through the chip and also a diode to permit other power schemes. Powering with the NANO regulator might be enough to make it work. So there might be a way, but I didn't look too hard. I also needed to buy the zener. Can't just buy one on the 'zon so i have a bag full.
-T
I am posting a few things that are duplicated from the PCM thread because they belong together.
In order to read out the FLASH content of the '97 Camaro PCM, you need to be able to access both banks of the TSide and also the Eside. I have put together a couple of command line apps that permit both TSide banks to be uploaded. I have found that GM did not implement mode $35. This mode would regularly be used as suggested by SAE J2190. The first task I undertook was to find a way to support mode $35. I did this by downloading a very small program into low memory. Using the Home Brew Cable (HBC) I first download the image to ram and execute it. This is done as follows:
Download Mode35_T.s19 /P9194 /C3 /V00
In this command line: Download.exe is the command, Mode35_T.s19 is the module I wish to install, /Pxxxx is the PCMs password, /C3 indicates HBC is installed on COM3 and /V00 just suppresses many of the comments placed in the code (if you want to see, try /VFF )
Once this command is accepted by the PCM, it is ready to upload from any address in the PCM.
I have a command line app that uses the PCM conditioned with the Mode35_T.s19 module to upload. The application is run using command line switches and generates an SRecord output file. This format is an often used way to store binary information along with addressing. It can easily be converted to a binary ( .bin file). This is done as follows:
Upload Output.S29 /C3 /B0 /S0E00 /L0200 /V00
In this command line: Upload .exe is the command, /C3 selects the serial port to use, /Bx selects which bank to upload (0 or 1 only), /Sxxxx sets the starting address of the upload in hex, /Lxxxx sets the length in hex, and /V00 just suppresses many of the comments placed in the code (if you want to see, try /VFF )
I am enclosing a sample output file named TSideEEPROM.s29 along with the various executables mentioned above.
-Tom
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