Discuss issues related to Calculator Hacking/Modding.
- Senior Member
- Posts: 94
- Joined: Sun Mar 27, 2016 10:24 am
- Location: France
- Calculators: Casio Afx 1.0, Casio fx-9750 G II, Casio fx-9860 GII
Found this today online, and as you told me OHP was only possible on USB, I'm quite surprised... is there any way to do OHP on serial?
- Senior Member
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- Joined: Sat Sep 15, 2012 6:59 am
- Location: Krautland ****
- Calculators: Casio fx-7400GII, Casio fx-7400GII (SH4), Casio fx-9750 G II, Casio fx-9750 G II (SH4), Casio fx-9860G, Casio fx-9860 G SD, Casio fx-9860G Slim, Casio fx-9860 GII SD, Casio fx-9860 GII SD Power Graphic 2, Casio Classpad 330 plus, Casio fx-CG 20, Casio Classpad fx-cp400, Casio fx-CG 50
They swapped the physical port order on the PCB with the fx-9860GII types. The calculator pictured here is a fx-9860G connected via USB to a OH 9860.cakeisalie5 wrote:Found this today online, and as you told me OHP was only possible on USB, I'm quite surprised... is there any way to do OHP on serial?
But indeed I see some possibilities to do OHP via the serial port:
1. OS enhancement.
The OS enhancement will be reliable but not widely accepted by the customers. Can be a very complicated process to achieve.
2. some persistent timer.
I did some experiments with persistent timers long ago. At present I do not know, if there is some persistent timer available with the actual OSes.
3. the UBC.
I use the UBC to redirect processing (an spool information via the serial port out of the redirection code) since years. I did it even with the fx-CG50 recently. It is more complicated with SH-3 calculators because they do not have the DBR.
4. With the above mentioned UBC-tool on SH-3 calculators I switched the interrupt-table to RAM (VBR) to redirect the UBC-interrupt-handler. Perhaps it is possible to abuse some other interrupt-handler, too.
In the latter three cases you have to find some unused area in RAM. This usually is OS-dependent. And - of course - there mustn't be another application which claims the same unused RAM area.
I'll be back!
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