Add-on modules for HP 200LX palmtop PC. USB-serial, WiFi, and maybe even more
I realized that while the USB-module is a piece of cake as there is USB power available, I have no such luck with the wireless module. So I need to figure some way to power the ESP-12F module and the level shifter. Couple of alternatives that came to mind:
Ideally I'd have power port that would accept anything between 3-6V, and convert that efficiently to whatever I'd need. For first revision, I'm kinda tempted to just throw a decent LDO in there and then add proper SMPS on later. It is somewhat questionable how much "real-world" use this will ever see anyways, so it should be fine. Besides, 2000mAh should last for something like 5 hours even with just LDO, so that doesn't sound that bad.
I will want to have some under-voltage protection to prevent brown-outs etc, even if I'm using protected cells or batteries that don't care.
A random reddit link that might be useful: https://www.reddit.com/r/esp8266/comments/4gmkfl/how_to_actually_run_an_esp8266_for_months_on_aa/
Found couple of other projects that are doing similar things. These two are somewhat C64-focused so the featureset does not exactly match my use. Still useful for reference. I would expect that there are probably tons of others too, considering how obvious this sort of project is.
https://github.com/bozimmerman/Zimodem This seems really feature-packed
Probably going to connect the remaining bizarro signals (DCD/DTR/DSR/RI) to GPIO and figure out them later.
ESP-12F pins: 7 GPIO13 UART0_CTS 16 GPIO15 UART0_RTS 21 RXD UART0_RXD 22 TXD UART0_TXD DB-9 / | ESP12 | Signal | Direction | Description 200LX | | | | -------+---------+----------+---------------+---------------------------- 1 | ? | DCD | Modem -> PC | Data Carrier Detect 2 | 22 | RxD | Modem -> PC | Received Data (by DTE) 3 | 21 | TxD | PC -> Modem | Transmitted Data (by DTE) 4 | ? | DTR | PC -> Modem | Data Terminal Ready 5 | 15 | GND | Common | Signal Ground 6 | ? | DSR | Modem -> PC | Data Set Ready 7 | 16 | RTS | PC -> Modem | Request To Send 8 | 7 | CTS | Modem -> PC | Clear To Send 9 | ? | RI | Modem -> PC | Ring Indicator 10 | | prot.GND | Common | Shield