<\/p>\n\n\n\n
Many Chinese microcontroller manufacturers develop awesome and cheap general-purpose MCUs using the popular 8051 architecture. There are many reasons for that but most importantly the 8051 architecture is a very common one that has been around for quite a long time. Secondly, manufacturing MCUs with 8051 DNA allows manufacturers to focus less on developing their own proprietary core and to give more effort in adding features. Holtek, Nuvoton, STC, etc are a few manufacturers to name. <\/p>\n\n\n\n
![\"\"](\"https:\/\/embedded-lab.com\/blog\/wp-content\/uploads\/2021\/12\/Untitled.jpg\")
<\/figure><\/div>\n\n\n\n\n\n\n\nRather than mastering a good old 8051-based microcontroller like the AT89C52 or similar, it is better to learn something new that has many similarities with that architecture. As mentioned earlier, STC has various flavour of microcontrollers based on 8051 cores. STC8A8K64S4A12 of the STC8 family is one such example. Here for this documentation, I will be using this MCU specifically. In short, it is a beast as it offers lot of additional hardware that are usually not seen in regular 8051s. Some key features are listed below. The red box highlights the STC8A8K64S4A12 micro in particular.<\/p>\n\n\n\n
![\"\"](\"https:\/\/embedded-lab.com\/blog\/wp-content\/uploads\/2021\/12\/image.png\")
<\/figure><\/div>\n\n\n\nI chose STC8A8K64S4A12 for this tutorial for all of its rich features. My favourite features include 12-bit ADC, multiple timers, reduced EMI feature and PCA module.<\/p>\n\n\n\n
![\"\"](\"https:\/\/embedded-lab.com\/blog\/wp-content\/uploads\/2021\/12\/image-1.png\")
<\/figure><\/div>\n\n\n\nNow let\u2019s see the naming convention of STC microcontrollers. The figure below shows us what the name of a STC8 micro means:<\/p>\n\n\n\n
![\"\"](\"https:\/\/embedded-lab.com\/blog\/wp-content\/uploads\/2021\/12\/image-2.png\")
<\/figure><\/div>\n\n\n\nThe name STC8A8K64S4A12 is quite a mouthful\nand given the nomenclature info, STC8A8K64SA412 is actually a STC8 series micro\nwith on-chip 12-bit ADC, 8kB SRAM, 64kB code space and 4 hardware serial (UART)\nports. Apart from these hardware thingies, the naming convention does not\nreveal other cool features, for if it had been so, the device name would be\neven longer. <\/p>\n\n\n\n
Initially I wanted to make this tutorial with the STC15F(L)204EA microcontroller but later I changed my mind because STC8A8K64S4A12 is much richer in hardware peripheral terms than STC15F(L)204EA, not to mention several similar hardware are present in both models of microcontroller. Since I planned to use STC8A8K64S4A12, I waited for the arrival of the board shown below before completing this work. Although this development board is an official board, it has been smartly designed for fast learning and rapid deployment of projects. As a matter of fact, if someone learns about this micro with this board, he\/she will rule over all of STC\u2019s 8051-based line-up.<\/p>\n\n\n\n This board has the following schematic and it will be needed throughout this tutorial. <\/p>\n\n\n\n On board, we have connectors for OLED display, GLCD, LCD, TFT Display, nRF24L01 transceiver, ESP8266 Wi-Fi module, etc. We also have on board W25x16 flash, 24C04 EEPROM, RS485 communication bridge and a CH340G USB-serial converter that doubles as an on-board programmer. <\/p>\n\n\n\n\n\n\n\n To deal with the vast array of peripherals of STC8A8K64S4A12,\nI needed something to quickly deploy projects without going through the\nregisters every time. Having gotten the idea of Board Support Package<\/strong>\n(BSP) while working with Nuvoton N76E003, it was time for me to develop\nsomething similar for STC micros here as officially STC does not have such\nbeautiful software implementation for their microcontrollers. However, STC does\nprovide lot of both C and assembly language examples in their reference manuals\nand programmer GUI unlike other manufacturers. Those examples, though helpful,\ndo not fit in all possible scenarios and often incomplete in terms of meaning.\nBy having a BSP, we can use our micro\u2019s hardware peripherals more efficiently\nwith ease and in a wide variety of ways. We would no longer need to create and\ncall functions for hardware peripherals every time. Nuvoton, TI,\nSTMicroelectronics, Silicon Labs and many other mainstream microcontroller\nmanufacturers are tooling various methods to reduce coding efforts and aid in\nrapid code development. <\/p>\n\n\n\n It is not an easy task to go through an\nentire reference manual, reading and trying out everything one-by-one. However,\nI had to do it no matter how painstaking job it was. This is because firstly, I\nhate setting registers repetitively every single time when I want to make a new\nproject and secondly, I want to make work easy so that less time, resource and\neffort are spent. I also have a tendency to forget things quickly. This solution will be as such that it can be\nmodified easily and ported for other STC microcontrollers as well.<\/p>\n\n\n\n I have developed my BSP for STC8A8K64S4A12 in an orderly fashion. There are header files for each hardware peripherals that contain all necessary functions and definitions. An example of STC8A8K64S4A12\u2019s watchdog timer\u2019s header file is shown below:<\/p>\n\n\n\n Now let\u2019s see what the registers and their settings look like:<\/p>\n\n\n\n As we can see there are\na whole bunch of settings that need attention while using. This is perhaps the\neasiest way to show what I wanted to achieve.<\/p>\n\n\n\n Please note that I have tested most of the\nstuffs that STC8A8K64S4A12 could offer. I tested them rigorously and with\nconfidence I can say all of these functions have been found to be okay. Being the sole\ndeveloper, I did my checks as much as possible but there could be unforeseen\nbugs that I may have overlooked. A typical case could be wrong function naming.\nThis is so because during development of these BSP files I made several changes\nwhen new issues appeared. Therefore, I would like to request readers to report\nany issue when discovered and I would also like readers to read the reference\nmanual of STC8 series completely if possible. <\/p>\n\n\n\n The examples presented in this document are based on my custom BSP and I believe that the journey with STC microcontroller supported by my BSP would be a joyful one. <\/p>\n\n\n\n\n\n\n\n The very first thing to do with a new microcontroller is to play with its GPIOs and this is what we will begin with. STC micros are based on 8051 architecture and so it is no surprise that the GPIOs will have similarities with typical 8051s. GPIOs of STC micros are essentially same as those of Nuvoton N76E003. Those who have seen my past Nuvoton tutorials<\/a> will find similarities. <\/p>\n\n\n\n Like always this first example is a simple variable flash rate LED flasher. Onboard LED connected to P5.5 and onboard push button connected to P5.2 are used. The board\u2019s schematic shows us that P5.2\u2019s push button must have an internal pull-up to properly function because it is not tied to any external pull-up resistor and P5.5\u2019s LED must be configured as an open-drain output. These are configured so in the setup function.<\/p>\n\n\n\n In the main loop, P5.5\u2019s LED state is toggled every 200ms. If P5.2\u2019s push button is pressed, P5.2\u2019s state changes and so additional 400ms delay is added, making the total toggling delay 600ms. <\/p>\n\n\n\n Note no clock settings are applied and the micro is running at default clock frequency of 24MHz.<\/p>\n\n\n\n![\"\"](\"https:\/\/embedded-lab.com\/blog\/wp-content\/uploads\/2021\/12\/image-3.png\")
<\/figure>\n\n\n\n![\"\"](\"https:\/\/embedded-lab.com\/blog\/wp-content\/uploads\/2021\/12\/image-4.png\")
<\/figure><\/div>\n\n\n\nMy Customized BSP<\/h2>\n\n\n\n
\/*
Watchdog Overflow Time = ((12 * 32768 * 2^(WDT_PS + 1)) \/ Sysclk)
*\/
#define WDT_div_factor_2 0x00
#define WDT_div_factor_4 0x01
#define WDT_div_factor_8 0x02
#define WDT_div_factor_16 0x03
#define WDT_div_factor_32 0x04
#define WDT_div_factor_64 0x05
#define WDT_div_factor_128 0x06
#define WDT_div_factor_256 0x07
#define WDT_set_prescalar(value) do{ \\
WDT_CONTR &= 0xF8; \\
WDT_CONTR |= value; \\
}while(0)
\/\/CNT_mode
#define WDT_stop_counting_in_idle_mode 0x00
#define WDT_continue_counting_in_idle_mode 0x08
#define WDT_start bit_set(WDT_CONTR, 5)
#define WDT_get_overflow_flag get_bit(WDT_CONTR, 7)
#define WDT_clear_overflow_flag bit_set(WDT_CONTR, 7)
#define WDT_reset bit_set(WDT_CONTR, 4)
#define WDT_clear do{ \\
WDT_CONTR = 0x00; \\
}while(0)
#define WDT_setup(CNT_mode, PS) do{ \\
WDT_clear; \\
WDT_CONTR |= CNT_mode; \\
WDT_set_prescalar(PS); \\
}while(0) <\/pre>\n\n\n\n![\"\"](\"https:\/\/embedded-lab.com\/blog\/wp-content\/uploads\/2021\/12\/image-5.png\")
<\/figure>\n\n\n\n![\"\"](\"https:\/\/embedded-lab.com\/blog\/wp-content\/uploads\/2021\/12\/image-6.png\")
<\/figure>\n\n\n\n![\"\"](\"https:\/\/embedded-lab.com\/blog\/wp-content\/uploads\/2021\/12\/image-7.png\")
<\/figure>\n\n\n\nGeneral Purpose Input-Output (GPIO)<\/h2>\n\n\n\n
![\"\"](\"https:\/\/embedded-lab.com\/blog\/wp-content\/uploads\/2021\/12\/image-8.png\")
<\/figure>\n\n\n\n![\"\"](\"https:\/\/embedded-lab.com\/blog\/wp-content\/uploads\/2021\/12\/image-9.png\")
<\/figure><\/div>\n\n\n\nBSP<\/h3>\n\n\n\n
\/\/P00
#define P00_quasi_bidirectional_mode do{bit_clr(P0M1, 0); bit_clr(P0M0, 0);}while(0)
#define P00_push_pull_mode do{P00_quasi_bidirectional_mode; bit_clr(P0M1, 0); bit_set(P0M0, 0);}while(0)
#define P00_input_mode do{P00_quasi_bidirectional_mode; bit_set(P0M1, 0); bit_clr(P0M0, 0);}while(0)
#define P00_open_drain_mode do{P00_quasi_bidirectional_mode; bit_set(P0M1, 0); bit_set(P0M0, 0);}while(0)
#define P00_pull_up_enable do{bit_set(P_SW2, 7); bit_set(P0PU, 0); bit_clr(P_SW2, 7);}while(0)
#define P00_pull_up_disable do{bit_set(P_SW2, 7); bit_clr(P0PU, 0); bit_clr(P_SW2, 7);}while(0)
#define P00_schmitt_trigger_enable do{bit_set(P_SW2, 7); bit_set(P0NCS, 0); bit_clr(P_SW2, 7);}while(0)
#define P00_schmitt_trigger_disable do{bit_set(P_SW2, 7); bit_clr(P0NCS, 0); bit_clr(P_SW2, 7);}while(0)
#define P00_high bit_set(P0, 0)
#define P00_low bit_clr(P0, 0)
#define P00_toggle bit_tgl(P0, 0)
#define P00_get_input get_bit(P0, 0) <\/pre>\n\n\n\nCode<\/h3>\n\n\n\n
#include \"STC8xxx.h\"
#include \"BSP.h\"
void setup(void);
void main(void)
{
setup();
while(1)
{
P55_toggle;
if(P52_get_input == 0)
{
delay_ms(400);
}
delay_ms(200);
};
}
void setup(void)
{
P55_open_drain_mode;
P52_input_mode;
P52_pull_up_enable;
} <\/pre>\n\n\n\nSchematic<\/h3>\n\n\n\n
![\"\"](\"https:\/\/embedded-lab.com\/blog\/wp-content\/uploads\/2021\/12\/image-10.png\")
<\/figure>\n\n\n\nExplanation<\/h3>\n\n\n\n
void setup(void)
{
P55_open_drain_mode;
P52_input_mode;
P52_pull_up_enable;
} <\/pre>\n\n\n\n P55_toggle;
if(P52_get_input == 0)
{
delay_ms(400);
}
delay_ms(200); <\/pre>\n\n\n\nDemo<\/h3>\n\n\n\n
![\"\"](\"https:\/\/embedded-lab.com\/blog\/wp-content\/uploads\/2021\/12\/image-11.png\")
<\/figure><\/div>\n\n\n\n