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Optimize MAX7456 driver invert and brightness functions 

Eliminate unnecessary register writes by keeping previous state information and only writing the registers when the related settings actually change. Saves 17 register writes per `clearScreen()` call.

Also fixed character invert flag handling. Previously changes to the flag would only affect subsequently drawn characters and previous characters would remain unchanged. So for static OSD elements it produced an inconsistent state. Now all characters immediately reflect the current state of the invert flag.

Results in appoximately a 33% reduction in processing time for the OSD task at default settings (~31us reduced to ~21us on F405).
This commit is contained in:
Bruce Luckcuck 2019-02-05 11:55:20 -05:00
parent af84f9e99d
commit f1e3c60dd9
1 changed files with 28 additions and 8 deletions
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36
src/main/drivers/max7456.c
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@ -226,6 +226,11 @@ static bool fontIsLoading = false;
static uint8_t max7456DeviceType;
// previous states initialized outside the valid range to force update on first call
#define INVALID_PREVIOUS_REGISTER_STATE 255
static uint8_t previousBlackWhiteRegister = INVALID_PREVIOUS_REGISTER_STATE;
static uint8_t previousInvertRegister = INVALID_PREVIOUS_REGISTER_STATE;
static void max7456DrawScreenSlow(void);
static uint8_t max7456Send(uint8_t add, uint8_t data)
@ -355,6 +360,11 @@ uint8_t max7456GetRowsCount(void)
return (videoSignalReg & VIDEO_MODE_PAL) ? VIDEO_LINES_PAL : VIDEO_LINES_NTSC;
}
static void max7456ClearShadowBuffer(void)
{
memset(shadowBuffer, 0, maxScreenSize);
}
void max7456ReInit(void)
{
uint8_t srdata = 0;
@ -392,6 +402,7 @@ void max7456ReInit(void)
}
// Set all rows to same charactor black/white level
previousBlackWhiteRegister = INVALID_PREVIOUS_REGISTER_STATE;
max7456Brightness(0, 2);
// Re-enable MAX7456 (last function call disables it)
__spiBusTransactionBegin(busdev);
@ -405,7 +416,7 @@ void max7456ReInit(void)
__spiBusTransactionEnd(busdev);
// Clear shadow to force redraw all screen in non-dma mode.
memset(shadowBuffer, 0, maxScreenSize);
max7456ClearShadowBuffer();
if (firstInit) {
max7456DrawScreenSlow();
firstInit = false;
@ -516,9 +527,15 @@ void max7456Invert(bool invert)
displayMemoryModeReg &= ~INVERT_PIXEL_COLOR;
}
__spiBusTransactionBegin(busdev);
max7456Send(MAX7456ADD_DMM, displayMemoryModeReg);
__spiBusTransactionEnd(busdev);
if (displayMemoryModeReg != previousInvertRegister) {
// clear the shadow buffer so all characters will be
// redrawn with the proper invert state
max7456ClearShadowBuffer();
previousInvertRegister = displayMemoryModeReg;
__spiBusTransactionBegin(busdev);
max7456Send(MAX7456ADD_DMM, displayMemoryModeReg);
__spiBusTransactionEnd(busdev);
}
}
/**
@ -531,11 +548,14 @@ void max7456Brightness(uint8_t black, uint8_t white)
{
const uint8_t reg = (black << 2) | (3 - white);
__spiBusTransactionBegin(busdev);
for (int i = MAX7456ADD_RB0; i <= MAX7456ADD_RB15; i++) {
max7456Send(i, reg);
if (reg != previousBlackWhiteRegister) {
previousBlackWhiteRegister = reg;
__spiBusTransactionBegin(busdev);
for (int i = MAX7456ADD_RB0; i <= MAX7456ADD_RB15; i++) {
max7456Send(i, reg);
}
__spiBusTransactionEnd(busdev);
}
__spiBusTransactionEnd(busdev);
}
//just fill with spaces with some tricks