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Diffstat (limited to 'docs/faq_debug.md')
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diff --git a/docs/faq_debug.md b/docs/faq_debug.md index f6cc729b6..5cc20251d 100644 --- a/docs/faq_debug.md +++ b/docs/faq_debug.md | |||
@@ -184,22 +184,15 @@ Pressing any key during sleep should wake host. | |||
184 | 184 | ||
185 | Arduino Leonardo and micro have **ATMega32U4** and can be used for TMK, though Arduino bootloader may be a problem. | 185 | Arduino Leonardo and micro have **ATMega32U4** and can be used for TMK, though Arduino bootloader may be a problem. |
186 | 186 | ||
187 | ## Enabling JTAG | ||
187 | 188 | ||
188 | ## Using PF4-7 Pins of USB AVR? | 189 | By default, the JTAG debugging interface is disabled as soon as the keyboard starts up. JTAG-capable MCUs come from the factory with the `JTAGEN` fuse set, and it takes over certain pins of the MCU that the board may be using for the switch matrix, LEDs, etc. |
189 | You need to set JTD bit of MCUCR yourself to use PF4-7 as GPIO. Those pins are configured to serve JTAG function by default. MCUs like ATMega*U* or AT90USB* are affected with this. | ||
190 | 190 | ||
191 | If you are using Teensy this isn't needed. Teensy is shipped with JTAGEN fuse bit unprogrammed to disable the function. | 191 | If you would like to keep JTAG enabled, just add the following to your `config.h`: |
192 | 192 | ||
193 | See this code. | 193 | ```c |
194 | #define NO_JTAG_DISABLE | ||
194 | ``` | 195 | ``` |
195 | // JTAG disable for PORT F. write JTD bit twice within four cycles. | ||
196 | MCUCR |= (1<<JTD); | ||
197 | MCUCR |= (1<<JTD); | ||
198 | ``` | ||
199 | https://github.com/tmk/tmk_keyboard/blob/master/keyboard/hbkb/matrix.c#L67 | ||
200 | |||
201 | And read **26.5.1 MCU Control Register – MCUCR** of ATMega32U4 datasheet. | ||
202 | |||
203 | 196 | ||
204 | ## Adding LED Indicators of Lock Keys | 197 | ## Adding LED Indicators of Lock Keys |
205 | You need your own LED indicators for CapsLock, ScrollLock and NumLock? See this post. | 198 | You need your own LED indicators for CapsLock, ScrollLock and NumLock? See this post. |