Electronics > Microcontrollers
Help to port a library from AVR to stm32!
kgavionics:
Hello guys
I'm trying to port a Nokia5110 display from AVR to Stm32, but I have a problem with printing characters stored on the flash, the rest is working fine!
The original library is using program space to read from the flash memory :
--- Code: ---void N5110_PrintStr(uint8_t x, uint8_t y, char *str, bool set)
{
uint8_t f_width = pgm_read_byte(&CurrentFont[0]);
uint8_t length = strlen(str);
for(int i = 0; i < length; i++)
{
N5110_PrintChar(x + (i * f_width), y, *str++, set);
}
}
--- End code ---
for the stm32, I just removed pgm_read_byte:
--- Code: ---void N5110_PrintStr(uint8_t x, uint8_t y, char *str, bool set)
{
uint8_t f_width = (&CurrentFont[0]);
uint8_t length = strlen(str);
for(int i = 0; i < length; i++)
{
N5110_PrintChar(x + (i * f_width), y, *str++, set);
}
}
--- End code ---
the fonts are stored like this:
--- Code: ---const uint8_t SmallFont[] =
{
/* Width, Height, Offset, Number */
0x06, 0x08, 0x20, 0x5f,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, // sp
0x00, 0x00, 0x00, 0x2f, 0x00, 0x00, // !
0x00, 0x00, 0x07, 0x00, 0x07, 0x00, // "
0x00, 0x14, 0x7f, 0x14, 0x7f, 0x14, // #
0x00, 0x24, 0x2a, 0x7f, 0x2a, 0x12, // $
0x00, 0x23, 0x13, 0x08, 0x64, 0x62, // %
0x00, 0x36, 0x49, 0x55, 0x22, 0x50, // &
0x00, 0x00, 0x05, 0x03, 0x00, 0x00, // '
0x00, 0x00, 0x1c, 0x22, 0x41, 0x00, // (
0x00, 0x00, 0x41, 0x22, 0x1c, 0x00, // )
0x00, 0x14, 0x08, 0x3E, 0x08, 0x14, // *
0x00, 0x08, 0x08, 0x3E, 0x08, 0x08, // +
0x00, 0x00, 0x00, 0xA0, 0x60, 0x00, // ,
0x00, 0x08, 0x08, 0x08, 0x08, 0x08, // -
0x00, 0x00, 0x60, 0x60, 0x00, 0x00, // .
0x00, 0x20, 0x10, 0x08, 0x04, 0x02, // /
0x00, 0x3E, 0x51, 0x49, 0x45, 0x3E, // 0
0x00, 0x00, 0x42, 0x7F, 0x40, 0x00, // 1
0x00, 0x42, 0x61, 0x51, 0x49, 0x46, // 2
0x00, 0x21, 0x41, 0x45, 0x4B, 0x31, // 3
0x00, 0x18, 0x14, 0x12, 0x7F, 0x10, // 4
0x00, 0x27, 0x45, 0x45, 0x45, 0x39, // 5
0x00, 0x3C, 0x4A, 0x49, 0x49, 0x30, // 6
0x00, 0x01, 0x71, 0x09, 0x05, 0x03, // 7
0x00, 0x36, 0x49, 0x49, 0x49, 0x36, // 8
0x00, 0x06, 0x49, 0x49, 0x29, 0x1E, // 9
0x00, 0x00, 0x36, 0x36, 0x00, 0x00, // :
0x00, 0x00, 0x56, 0x36, 0x00, 0x00, // ;
0x00, 0x08, 0x14, 0x22, 0x41, 0x00, // <
0x00, 0x14, 0x14, 0x14, 0x14, 0x14, // =
0x00, 0x00, 0x41, 0x22, 0x14, 0x08, // >
0x00, 0x02, 0x01, 0x51, 0x09, 0x06, // ?
0x00, 0x32, 0x49, 0x59, 0x51, 0x3E, // @
0x00, 0x7C, 0x12, 0x11, 0x12, 0x7C, // A
0x00, 0x7F, 0x49, 0x49, 0x49, 0x36, // B
0x00, 0x3E, 0x41, 0x41, 0x41, 0x22, // C
0x00, 0x7F, 0x41, 0x41, 0x22, 0x1C, // D
0x00, 0x7F, 0x49, 0x49, 0x49, 0x41, // E
0x00, 0x7F, 0x09, 0x09, 0x09, 0x01, // F
0x00, 0x3E, 0x41, 0x49, 0x49, 0x7A, // G
0x00, 0x7F, 0x08, 0x08, 0x08, 0x7F, // H
0x00, 0x00, 0x41, 0x7F, 0x41, 0x00, // I
0x00, 0x20, 0x40, 0x41, 0x3F, 0x01, // J
0x00, 0x7F, 0x08, 0x14, 0x22, 0x41, // K
0x00, 0x7F, 0x40, 0x40, 0x40, 0x40, // L
0x00, 0x7F, 0x02, 0x0C, 0x02, 0x7F, // M
0x00, 0x7F, 0x04, 0x08, 0x10, 0x7F, // N
0x00, 0x3E, 0x41, 0x41, 0x41, 0x3E, // O
0x00, 0x7F, 0x09, 0x09, 0x09, 0x06, // P
0x00, 0x3E, 0x41, 0x51, 0x21, 0x5E, // Q
0x00, 0x7F, 0x09, 0x19, 0x29, 0x46, // R
0x00, 0x46, 0x49, 0x49, 0x49, 0x31, // S
0x00, 0x01, 0x01, 0x7F, 0x01, 0x01, // T
0x00, 0x3F, 0x40, 0x40, 0x40, 0x3F, // U
0x00, 0x1F, 0x20, 0x40, 0x20, 0x1F, // V
0x00, 0x3F, 0x40, 0x38, 0x40, 0x3F, // W
0x00, 0x63, 0x14, 0x08, 0x14, 0x63, // X
0x00, 0x07, 0x08, 0x70, 0x08, 0x07, // Y
0x00, 0x61, 0x51, 0x49, 0x45, 0x43, // Z
0x00, 0x00, 0x7F, 0x41, 0x41, 0x00, // [
0xAA, 0x55, 0xAA, 0x55, 0xAA, 0x55, // Backslash (Checker pattern)
0x00, 0x00, 0x41, 0x41, 0x7F, 0x00, // ]
0x00, 0x04, 0x02, 0x01, 0x02, 0x04, // ^
0x00, 0x40, 0x40, 0x40, 0x40, 0x40, // _
0x00, 0x00, 0x03, 0x05, 0x00, 0x00, // `
0x00, 0x20, 0x54, 0x54, 0x54, 0x78, // a
0x00, 0x7F, 0x48, 0x44, 0x44, 0x38, // b
0x00, 0x38, 0x44, 0x44, 0x44, 0x20, // c
0x00, 0x38, 0x44, 0x44, 0x48, 0x7F, // d
0x00, 0x38, 0x54, 0x54, 0x54, 0x18, // e
0x00, 0x08, 0x7E, 0x09, 0x01, 0x02, // f
0x00, 0x18, 0xA4, 0xA4, 0xA4, 0x7C, // g
0x00, 0x7F, 0x08, 0x04, 0x04, 0x78, // h
0x00, 0x00, 0x44, 0x7D, 0x40, 0x00, // i
0x00, 0x40, 0x80, 0x84, 0x7D, 0x00, // j
0x00, 0x7F, 0x10, 0x28, 0x44, 0x00, // k
0x00, 0x00, 0x41, 0x7F, 0x40, 0x00, // l
0x00, 0x7C, 0x04, 0x18, 0x04, 0x78, // m
0x00, 0x7C, 0x08, 0x04, 0x04, 0x78, // n
0x00, 0x38, 0x44, 0x44, 0x44, 0x38, // o
0x00, 0xFC, 0x24, 0x24, 0x24, 0x18, // p
0x00, 0x18, 0x24, 0x24, 0x18, 0xFC, // q
0x00, 0x7C, 0x08, 0x04, 0x04, 0x08, // r
0x00, 0x48, 0x54, 0x54, 0x54, 0x20, // s
0x00, 0x04, 0x3F, 0x44, 0x40, 0x20, // t
0x00, 0x3C, 0x40, 0x40, 0x20, 0x7C, // u
0x00, 0x1C, 0x20, 0x40, 0x20, 0x1C, // v
0x00, 0x3C, 0x40, 0x30, 0x40, 0x3C, // w
0x00, 0x44, 0x28, 0x10, 0x28, 0x44, // x
0x00, 0x1C, 0xA0, 0xA0, 0xA0, 0x7C, // y
0x00, 0x44, 0x64, 0x54, 0x4C, 0x44, // z
0x00, 0x00, 0x10, 0x7C, 0x82, 0x00, // {
0x00, 0x00, 0x00, 0xFF, 0x00, 0x00, // |
0x00, 0x00, 0x82, 0x7C, 0x10, 0x00, // }
0x00, 0x00, 0x06, 0x09, 0x09, 0x06 // ~ (Degrees)
};
--- End code ---
Can someone tell me what I'm doing wrong! TIA
brucehoult:
--- Code: ---pgm_read_byte(&CurrentFont[0]);
--- End code ---
You should consider how you would actually implement pgm_read_byte for the ARM...
--- Code: ---char pgm_read_byte(char *p){
return *p;
}
--- End code ---
... and then do the same actions instead of the call.
(and then simplify the resulting code, though it's not necessary as the compiler will do that for you)
SiliconWizard:
--- Quote from: kgavionics on May 28, 2023, 11:57:47 pm ---for the stm32, I just removed pgm_read_byte:
--- Code: ---void N5110_PrintStr(uint8_t x, uint8_t y, char *str, bool set)
{
uint8_t f_width = (&CurrentFont[0]);
--- End code ---
--- End quote ---
You're assigning the address of the item instead of its value.
hans:
Since the font is marked 'const', it is stored in FLASH. AVR and some other 8-bit MCUs uses a Harvard architecture. This means the FLASH memory has its own address space. You can get pointers to things that are stored in FLASH, but dereferencing it with '*pointer' would read it from the data memory instead. So that's why AVRs use pgm_read_byte, which internally use a special instruction of the CPU to read FLASH data.
On ARM and many other architectures that can support a wider address bus, they have chosen for a Von Neumann architecture. Here instruction and data are within the same address space, and so you don't need special instructions anymore. You can just replace pgm_read_byte by the a placeholder as bruce shows. If you turn on the compiler optimizer (if you need the speed), that function will disappear in its enterity.
kgavionics:
--- Quote from: brucehoult on May 29, 2023, 12:15:22 am ---
--- Code: ---pgm_read_byte(&CurrentFont[0]);
--- End code ---
You should consider how you would actually implement pgm_read_byte for the ARM...
--- Code: ---char pgm_read_byte(char *p){
return *p;
}
--- End code ---
... and then do the same actions instead of the call.
(and then simplify the resulting code, though it's not necessary as the compiler will do that for you)
--- End quote ---
Thank you, brucehoult, your solution worked like a charm!
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