12/8/2022 0 Comments Teensy as spi programmer![]() That was actually a big improvement, but as libraries like ST7735 were developed, this became a problem. The early Teensy 3.1 cards dropped the numbers. The numbers confused a lot of people, since the convention Arduino and other uses, which we follow for everything else, uses the number to mean which port is belongs to. The original Teensy 3.0 card has these labeled CS0, CS1, CS2, CS3, CS4. Four of the 5 can route to 2 different pins.ĬS on pin 20 is the same as CS on pin 23.ĬS on pin 21 is the same as CS on pin 22. The main problem is there really are only 5 of those special signals inside the chip. This was done to simplify the pinout card. Pretty much everything else uses the pins as normal digital outputs.ĭoes anyone (Paul) know why the SPI CS on D2, D6, D22, D23 have disappeared in the move from 3.1 to 3.2. ![]() The optimized display libs, ILI9341_t3, ST7735 and TFT_ILI9163C are the main ones. Only a few very special libraries actually use those special CS pins. Hardware CS might even be slightly slower in some cases, depending on arcane details of how the compiler generates code with constants and how the flash memory cache works inside the chip. You'd think automatic CS signals would be faster, and indeed in some very special cases they are, but for normal libraries the extra overhead to enable the automatic signal works out to be about the same as just controlling a digital pin through a pointer (the common speedup technique used in many Arduino libs). But it doesn't happen automatically unless special Teensy-specific code enables it, so it's only sort-of automatic. Those pins labeled CS have special hardware which can automatically create the CS signal. This is true for all SPI-based libraries designed for regular Arduino boards which don't have special Teensy-specific optimizations. ![]() You can use SD.begin(4) to use pin 4, and it works fine even though pin 4 isn't labeled as CS on the card. For example, the SD library uses normal digital output. Before I answer this, please understand most SPI-based programs and libraries create their chip select signals using normal digital outputs.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |