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58 lines
2.0 KiB
Markdown
58 lines
2.0 KiB
Markdown
---
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title: HP 50g and missed keypresses
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layout: default
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language: en
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created: 2017-03-18 22:29:30 +0100
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updated: 2017-03-18 22:29:30 +0100
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toc: false
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tags:
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- know-how
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- hardware
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- hp
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- 50g
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- calculator
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---
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The default key debouncing wait time in the HP 50g is very long so that it misses lots of
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keypresses when typing fast. E.g. when typing `500` the calculator only registers `50`. This
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behaviour is controlled by the `KEYTIME` setting.
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The `KEYTIME` setting specifies the number of processor ticks, any further keypresses are ignored
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after a key was pressed. The default value is **1138** which resembles about 140 ms.
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Setting this to e.g. **500** (~61 ms) makes entering numbers much more reliable. Some users even
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disabled it by setting it to **0** and had no problems at all.
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Changing the value
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==================
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To set the `KEYTIME` setting to **500**, press the following keys (in RPN mode):
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1. <kbd>5</kbd><kbd>0</kbd><kbd>0</kbd>
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1. <kbd>ENTER</kbd>
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1. <kbd>ALPHA</kbd><kbd>ALPHA</kbd>
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1. <kbd>K</kbd><kbd>E</kbd><kbd>Y</kbd><kbd>T</kbd><kbd>I</kbd><kbd>M</kbd><kbd>E</kbd>
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1. <kbd>STO ▶</kbd>
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But this only works for the current session. After a reboot of the device, the value will be back
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to the default value of **1138** again.
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Changing the value on bootup
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============================
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To have this value changed on every bootup of the calculator, we have to save the instructions
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to a special variable called `STARTUP`. To do this, press the following keys (in RPN mode):
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1. <kbd>↱</kbd><kbd>+</kbd> (this will insert `<< >>` and place the cursor in the middle)
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1. <kbd>5</kbd><kbd>0</kbd><kbd>0</kbd>
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1. <kbd>↱</kbd><kbd>0</kbd> (this will insert a `→`)
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1. <kbd>ALPHA</kbd><kbd>ALPHA</kbd>
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1. <kbd>K</kbd><kbd>E</kbd><kbd>Y</kbd><kbd>T</kbd><kbd>I</kbd><kbd>M</kbd><kbd>E</kbd>
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1. <kbd>ENTER</kbd>
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1. <kbd>S</kbd><kbd>T</kbd><kbd>A</kbd><kbd>R</kbd><kbd>T</kbd><kbd>U</kbd><kbd>P</kbd>
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1. <kbd>STO ▶</kbd>
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This stores the instruction into the special variable `STARTUP` which gets evaluated on every
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bootup.
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