tones: keep frequencies in tone tables in 8.8 fixed point format The phase calculation is already done using fixed point math, so we can trivially feed it tone frequencies in the same format. This results in the tones being closer to the desired frequencies. E.g., a E6 will sound as 1319 Hz (as it should) instead of 1344 Hz as before. Signed-off-by: Josef 'Jeff' Sipek <jeffpc@josefsipek.net>
main: do phase math using a uint16_t fixed point Using integer math for the phase calculation limits the tone frequencies to rather large discrete steps. When we represent a frequency as how many wave array steps we make per sample relative to 1 Hz, we get about 64 possible frequencies (assuming 16384 Hz sample rate and 256 entry wave array): > c(0:64)*(16384/256) [1] 0 64 128 192 256 320 384 448 512 576 640 704 768 832 896 [16] 960 1024 1088 1152 1216 1280 1344 1408 1472 1536 1600 1664 1728 1792 1856 [31] 1920 1984 2048 2112 2176 2240 2304 2368 2432 2496 2560 2624 2688 2752 2816 [46] 2880 2944 3008 3072 3136 3200 3264 3328 3392 3456 3520 3584 3648 3712 3776 [61] 3840 3904 3968 4032 4096 That is, we get frequencies that are multiples of 64 Hz. This are pretty substantial steps and makes many musical patterns sound out of tune. Instead of using a uint8_t to describe the frequency and the current phase, we could use more bits with an implied decimal point some number of bits in. This would allow us to calculate more accurately, and then simply round the index or interpolate between two values when doing the wave array lookup. This commit switches the phase calculation to uint16_t used as a 8.8 fixed point number. That is, given a phase x, the real world phase is x / 256. Signed-off-by: Josef 'Jeff' Sipek <jeffpc@josefsipek.net>
Use ARRAY_LEN instead of sizeof to detect end of fixed tone pattern The two are equivalent for uint8_t, but break if the type changes to something larger. Signed-off-by: Josef 'Jeff' Sipek <jeffpc@josefsipek.net>
tones: add a helper macro to convert from Hz to steps Signed-off-by: Josef 'Jeff' Sipek <jeffpc@josefsipek.net>
Use symmetry to store only 1/4 of a sine wave This shrinks the sine_wave array by 190 bytes, but requires a bit more complex code to calculate any value which takes up 42 extra bytes of flash. So, overall we save 148 bytes of flash. text data bss dec hex filename 1530 2 33 1565 61d fmfox-atmega48p.elf (before) 1382 2 33 1417 589 fmfox-atmega48p.elf (after) Additionally, this fixes slight offset in the negative half-cycle. Previously, the mean of the sine wave was 127.5 instead of 128 as one would expect from a sine wave. Signed-off-by: Josef 'Jeff' Sipek <jeffpc@josefsipek.net>
gen-eeprom: fix typo in usage message Signed-off-by: Josef 'Jeff' Sipek <jeffpc@josefsipek.net>
Don't open-code mcu_set_clock_prescalar Signed-off-by: Josef 'Jeff' Sipek <jeffpc@josefsipek.net>
Remove redundant code The most recent merge with avr-common brings us these macros via arch.h. Therefore the ones in main.c are redundant. Signed-off-by: Josef 'Jeff' Sipek <jeffpc@josefsipek.net>
Merge avr-common Signed-off-by: Josef 'Jeff' Sipek <jeffpc@josefsipek.net>
arch.h: add ARRAY_LEN Signed-off-by: Josef 'Jeff' Sipek <jeffpc@josefsipek.net>
arch: add MCU_RAW_FREQ for ATmega48P Signed-off-by: Josef 'Jeff' Sipek <jeffpc@josefsipek.net>
arch: move most of generic code into arch/generic_*.h Signed-off-by: Josef 'Jeff' Sipek <jeffpc@josefsipek.net>
arch: add mcu_set_clock_prescalar helper A more advanced version would disable interrupts if they are enabled to avoid an interrupt mid-function breaking the back-to-back instruction requirement. Signed-off-by: Josef 'Jeff' Sipek <jeffpc@josefsipek.net>
arch: add __set_pin static inline This is a low-overhead function to set/clear a GPIO pin. Signed-off-by: Josef 'Jeff' Sipek <jeffpc@josefsipek.net>
arch: add PIN_{INPUT,OUTPUT}_* macros
These can be used to construct the PORT and DDR register values in more
semantically readable way.
Signed-off-by: Josef 'Jeff' Sipek <jeffpc@josefsipek.net>
manual: proofreading pass by Holly At this point, the manual should be done. Signed-off-by: Josef 'Jeff' Sipek <jeffpc@josefsipek.net>
manual: add a check for current draw to the step-by-step instructions Signed-off-by: Josef 'Jeff' Sipek <jeffpc@josefsipek.net>
manual: include the BOM in an appendix Signed-off-by: Josef 'Jeff' Sipek <jeffpc@josefsipek.net>
manual: minor edit to the construction chapter Signed-off-by: Josef 'Jeff' Sipek <jeffpc@josefsipek.net>
manual: address remaining datasheet todo items Signed-off-by: Josef 'Jeff' Sipek <jeffpc@josefsipek.net>