With this, I am able to get farther into the connection sequence:
I found that I can get 3 different error messages in Okasan no Famicom Trade when connecting now:
- Originally, with no phone line connected, Error 4001. CPU2 replies with message 80 01 00 01.
- Never removing the dial tone, Error 4003. CPU2 replies with message 80 01 00 03.
- Dials the number, but no server connected to respond, Error 4006. CPU2 replies with message 80 01 00 06.
- Before I did the dial tone, I had just the 100k and DC supply.
- I tested the DC supply incrementally up to 30V (max of this supply I had handy).
- The Famicom Network System always squashes it down to about 2V when picking up regardless. I stuck with 5V. (No use having 30V flying around.)
- 400Hz simulates the Japanese dial tone, which is different than USA.
- I found range 55Hz - 10.6kHz can actually be detected as a dial tone.
- 55Hz - 100Hz not always work but does if you retry a couple times.
- I did not try to simulate the USA or UK style dial tones that have the dual frequencies that produce a 3rd beat frequency.
- 2V peak-to-peak at 400Hz was not enough for it to think there was a dial tone.
- Without the DC offset on the dial tone, it does not think there is a dial tone.
- It works when offset by only 2V (i.e. line the peak up with GND). I bumped it a little farther based on no scientific basis to do that.
- Red and Green lines can be swapped and everything works the same.
- I hear none of this through the TV speakers.
- I mentioned earlier that I had heard tone dialing following an intentional RAM corruption of CPU2. So it is capable but apparently not happening here for some reason.